B

REVIEW OF

LITERATURE

9

2. REVIEW OF LITERATURE

Presently, urban Indian population is going through a phase of dietary transition;

people have started opting for commercially available packaged foods or quick

homemade foods (Misra et al, 2009a). These snacks often regarded as “comfort/

convenience/ ready to eat foods” are quickly prepared or are available

commercially anywhere anytime. Of all the countries, India is one of the largest

snack markets and people consume more than 400,000 tonnes of snacks every

year. These so called “comfort foods” include fried foods that are high in energy

(particularly fats) and low in other nutrients (Agrawal et al, 2008). These faulty

dietary habits have contributed to increased incidence of lifestyle related non

communicable diseases including obesity, the metabolic syndrome, type 2

diabetes mellitus (T2DM) and cardiovascular diseases (Misra and Khurana, 2008;

Bhardwaj et al, 2008). Figure 2.1 highlights the relationship between nutrition

transition, urbanization, and the rise in obesity, the metabolic syndrome and

T2DM in developing countries including India (Misra et al, 2010). Most of these

commercially prepared foods contain Trans fatty acids, also called Trans Fatty

acids (TFA), are coming from Vanaspati - the partially hydrogenated vegetable

oils, which is used for its low cost and longer shelf life. Also, due to ignorance or

to save resources, the oil after frying is used repeatedly not only at commercial

outlets but even at household level, leading to the generation of free radicals

(Martin et al, 2007; Donnelly and Robinson, 1995) and reportedly some TFAs,

making the oil unfit for consumption.

The developing world, especially the South Asian countries are facing the menace

of TFAs. In this region, the use of partially hydrogenated vegetable oils (vanaspati

ghee) in deep-fat frying of culinary items, such as samosa, paratha, poori/

bhatura, tikkie etc, results in increased consumption of TFAs (Butt et al, 2009). In

India, due to ignorance among consumers, scarcity of data on the TFA content of

fried/ baked foods, their formation in re-heated oils or their consumption through

Indian dietaries, no stringent guidelines to curb their intake, and resulting in

10

harmful effects of high TFA consumption. Presently the limited data available in

India on the TFA content of food articles are calculated on the basis of TFAs

present in the raw ingredients and not on the laboratory analysis of cooked food

items (Agrawal et al, 2008). Most importantly, Indian consumer today is

incognizant of the amount of TFAs present in such foods and lacks the

understanding of the actual amount of TFAs (s)he is consuming during the day.

The population in general is ignorant of the adverse effects of TFAs on various

body organs including heart.

*: Pattern 3 may be seen at different rates of progression in different developing countries, # : Likely to

affect all socio-economic strata

Figure 2.1: Relationship between nutrition transition, urbanization, and the rise in

obesity and the metabolic syndrome in developing countries (Source: Misra et al,

2010)

Pattern 1:

Diets rich in carbohydrates, fiber, low in fats, saturated

fats, high activity profile & lean body phenotype

Pattern 2:

Famine-like situation, low calorie, low protein and fat

diets, low body fat and fat-free mass, growth retardation

Improved food supply, Increased food availability (longer shelf life, 24-

hour supermarkets), Competitive prices of energy dense foods

Pattern 5:

Increase intake of; improved quality of fat,

green leafy vegetables, and fiber; decreased

intake of refined carbohydrates, energy-

dense foods

Pattern 4 #:

Rise of obesity, the metabolic

syndrome and type 2 diabetes

mellitus (T2DM)

Pattern 3 *:

Decreasing food scarcity and

famine, labor intensive work

Increased intake of fat, salt and sugar

Dietary liberalization and “westernization”

Demographic Changes:

Rural-urban migration,

increasing elderly

population, Mechanization

Economic Changes:

Urbanization, open

market economy,

increasing affluence

11

Also, since the quality of oil degrades during heat treatment (both at the industrial

level/ large scale cooking and at home) it is necessary to estimate the TFA content

of the fat subjected to heating/ repeated heating. Thus, research on TFAs and

education of the masses, particularly the women is of utmost importance, given

the alarmingly rising trend of diabetes, cardiovascular diseases and the metabolic

syndrome in India.

2.1 DIETARY FATS AND FATTY ACIDS

Fats and oils are the major components of our diet. In addition to being a

concentrated source of energy, dietary fats have several physiological functions

such as providing essential fatty acids, facilitating the delivery of fat soluble

vitamins, improving texture and palatability of the foods as well as contributing to

the satiety. The nutritional and health benefits of dietary fats depend on the type of

fatty acids and the minor components such as tocopherols, tocotrienols,

phytosterols etc present in the non-glyceride fraction of the vegetable oils.

Therefore, the current recommendations on dietary fats are now laying emphasis

on the type of fat rather than on the quantity alone. The pathogenesis of several

diet related chronic diseases such as cardiovascular diseases, type 2 diabetes

mellitus, hypertension, inflammatory bowel disease, certain types of cancers,

neurological and neuropsychiatric disorders are directly or indirectly related to

dietary fats.

Fats, oils or lipids consist of a large number of organic compounds including fatty

acids, monoacylglycerols, diacylglycerols, triacylglycerols (TG), phospholipids

(PL), eicosanoids, docosanoids, resolvins, sterols, sterol esters, carotenoids,

retinol, tocopherol, tocotrienols, fatty alcohols, hydrocarbons and wax esters

(FAO, 2008). Classically, lipids were defined as substances that are soluble in

organic solvents. This however, is a loose definition and could include a number

of non-lipid organic compounds. A chemically novel definition and

comprehensive system of classification of lipids were proposed in 2005 which

defines lipids as “small hydrophobic or amphipathic (or amphiphilic) molecules

that may originate entirely or in part by condensations of thioesters and/or

12

isoprene units”. The proposed lipid classification system enables the cataloguing

of lipids and their properties in a way that is compatible with other

macromolecular data bases. Using this approach, lipids from biological tissues

have been divided into 8 categories (Table 2.1) containing distinct classes and

subclasses of molecules (FAO, 2008; Fahy et al, 2005).

Table 2.1: Categories of lipid with typical examples

(FAO, 2008)

Category Example Category Example

Fatty acids Oleic acid Sterol lipids Cholesterol

Glycerolipids Triacylglycerol Prenol lipids Farnesol

Glycerophospholipids Phosphatidylcholine

Saccharolipids UDP-3-0-(3hydroxy-

tetradecanoyl)-N-

acetylglucosamine

Sphingolipids Sphingosine Polyketides Aflatoxin

2.1.1 Fats and Fatty Acids

Chemically, fatty acid is a carboxylic acid with an aliphatic tail (chain). These are

a diverse group of molecules, characterized by a repeating series of methylene

groups that impart hydrophobic character. The fatty acid structure represents the

major lipid building block of complex lipids and therefore, is one of the most

fundamental categories of biological lipids. This lipid class includes the various

types of fatty acids, eicosanoids, fatty alcohols, fatty aldehydes, fatty esters, fatty

amides, fatty ethers and hydrocarbons. Many members of this category,

especially the eicosanoids, derived from n-6 and n-3 polyunsaturated fatty acids

(PUFAs), have distinct biological activities. The fatty acids present in various

lipid molecules are the major components of dietary fats. In the body, they are

incorporated in blood lipids, in fats deposits and in structural lipids in biological

membranes.

Dietary fatty acids are derived from acylglycerols, free fatty acids, phospholipids

and sterol esters. Of these, triglycerides (TG) are the main sources. The physical

and chemical characteristics as well as the health and nutritional effects of dietary

fatty acids are influenced greatly by the kinds and proportions of the component

13

fatty acids. The predominant fatty acids are straight chain, can be saturated or

unsaturated (containing one or more carbon-carbon double bonds) with an even

number of carbon atoms. Fatty acids containing 1 double bond are called

‘monounsaturated fatty acids’ (MUFA) and those with two or more double bonds

are called ‘polyunsaturated fatty acids’ (PUFA). A cis configuration means that

the hydrogen atoms at the double bonds are on the same side of the chain while in

a trans configuration they are on opposite sides. In almost all the naturally

occurring PUFAs the double bond exists in a methylene (CH2) interrupted pattern

i.e. the double bonds are in non-conjugated position. In most of the naturally

occurring unsaturated fatty acids, the double bonds are in the cis configuration and

are typically positioned at the 3rd

(ω3/ n-3), 6th

(ω6/ n-6), or 9th

(ω9/ n-9) carbon

atom from the terminal methyl group.

2.1.2 Nomenclature of fatty Acids

There are a number of systems of nomenclature for fatty acids, but some do not

provide sufficient information on their structure. A chemical name must describe

the chemical structure unambiguously. The systematic nomenclature

recommended by the International Union of Pure and Applied Chemistry

(IUPAC-IUB Commission on Nomenclature, 1978) names the fatty acids on the

basis of the number of carbon atoms as well as the number and position of

unsaturation relative to the carboxyl group (Table 2.2). In addition the

configuration of double bonds, location of branched chains and hetero atoms and

other structural features are also specified. The carbon atom of the carboxyl group

is considered to be first and the carbons in the fatty acid chain are numbered

consequently from the carboxylic carbon (FAO, 2008).

By convention, a specific double bond in a chain is identified by the lower number

of the two carbons it joins. The double bonds are labeled with Z or E where

appropriate but are very often replaced by the terms cis and trans, respectively.

For example, the systematic name of linoleic acid (LA) is “Z-9, Z-12-

octadecadienoic acid” or “cis-9, cis-12-octadecadienoic acid”. Although the

IUPAC nomenclature is precise and technically clear, the fatty acid names are too

14

long and therefore, for convenience, ‘trivial’ or historical names and shorthand

notations are frequently used in scientific writings. There are several shorthand

notations for dietary fatty acids, but all of them adopt the form C: D, where C is

the number of carbon atoms and D is the number of double bonds in the carbon

chain.

Biochemists and nutritionists very often use the “n minus” system of notation for

naturally occurring cis unsaturated fatty acids. The term “n minus” refers to the

position of the double bond of the fatty acid closest to the methyl end of the

molecule. This system defines easily the different metabolic series, such asn-9, n-

6 and n-3, etc. The “n minus” system is applicable only to cis unsaturated fatty

acids and to those cis polyunsaturated fatty acids whose double bonds are

arranged in a methylene interrupted manner. LA, which has its second double

bond located at6 carbons from the methyl end, is abbreviated to 18:2n-6. The “n

minus” system is also referred to as the omega system. (IUPAC-IUB Commission

on Nomenclature, 1978).

Another system widely used is the delta (Δ) system, in which the classification is

based on the number of carbon atoms interposed between the carboxyl carbon and

the nearest double bond to the carboxylic group. This system specifies the position

of all the double bonds as well as their cis/trans configuration. It is applicable to a

large number of fatty acids, except those with branched chains, hetero atoms,

triple bonds and other fatty acids with unusual structural features. According to

the delta system, the shorthand notation for LA is “cis-Δ9, cis-Δ12-18:2”. For

convenience, it could be expressed as “cis,cis-Δ9,Δ12-18:2”. In some scientific

papers, authors drop the “Δ” notation and write it simply as “cis-9,cis-12-18:2” or

“9c,12c-18:2”.

In edible fats/ oils, the fatty acids are commonly classified as per the length of

carbon chain and their degree of saturation/ unsaturation. Fatty acids vary in

carbon chain length ranging from 2 to 80 carbons, but are typically present in food

as 14, 16, 18, 20 and 22 carbon atom chains. Fats varying in fatty acid chain

lengths are metabolized differently.

15

Based on the length of carbon chain, fatty acids are classified as short chain,

medium chain or long chain fatty acids.

Short chain fatty acids contain 2-8 carbon atoms, such as butyric acid (C-

4) or propionic acid (C-3). They are formed in the gut when

polysaccharides are fermented by the anaerobic bacteria present in the

large intestine. Short-chain fatty acids, just as medium-chain fatty acids,

are taken up directly to the portal vein during lipid digestion (Bird et al,

2000).

Medium chain fatty acids contain 6 to 12 carbons atoms. Triglycerides

containing medium chain fatty acids are known as Medium Chain

Triglycerides (MCTs). These are medium chain fatty acid esters of

glycerol. They are directly absorbed into the portal circulation and

transported to the liver for rapid oxidation (Scalfi et al, 1991). MCTs

passively diffuse from the GI tract to the portal system without requiring

any modification like long-chain fatty acids. In addition, MCTs do not

require bile salts for digestion. Patients suffering from malnutrition or

malabsorption syndromes are treated with MCTs because they do not

require energy for absorption, utilization, or storage. Coconut oil is

composed of approximately 66% medium-chain triglycerides. Other rich

sources of MCTs include palm kernel oils and camphor tree drupes.

Long chain fatty acids contain 12 or more carbon atoms. However, this

term is often used to describe the longer chain fatty acids that contain more

than 20 carbon atoms, which may also be referred to as very long chain

fatty acids. Long chain fatty acids are first acted upon by bile salts leading

to their emulsification and later these are absorbed into the lymphatic

system.

Based on the saturation/ unsaturation fatty acids are classified as saturated and

unsaturated fatty acids.

Saturated Fatty Acids (SFAs) contain only single (carbon-to-carbon)

bonds. Most of the SFAs occurring in nature have unbranched structures

and an even number of carbon atoms (Table 2.3). They have the general

16

formula R-COOH; and are represented by the number of carbon atoms

with zero double bonds (stearic acid; C18:0). SFAs are chemically the

least reactive and therefore they are more stable and have a longer shelf

life than the unsaturated fatty acids. The melting point of SFAs increases

with the chain length. Decanoic and longer chain fatty acids are solid at

normal room temperature. The SFAs are further classified into 4

subclasses according to chain lengths: short, medium, long and very long.

Since various definitions are used in the literature for the SFA subclasses

the FAO (2008) recognized that there is a need for universal definitions

and recommends the following:

Short-chain fatty acids: between 3 and 7 carbon atoms e.g. Butyric acid

(4: 0) and caproic acid (6: 0)

Medium-chain fatty acids: between 8 and 13 carbon atoms e.g.

Caprylic acid (8: 0), capric acid (10: 0) and lauric acid (12: 0)

Long-chain fatty acids: between 14 and 20 carbon atoms e.g. Palmitic

acid (16: 0) and stearic acid (18: 0). Palmitic acid is the most widely

occurring SFA, being present in practically every fat examined, it is

present in marine oils, in the milk and depot fats of land animals and in

vegetable fats; main sources include palm oil, cottonseed oil, lard and

beef tallow. Stearic acid is present in most vegetable fats, though a

significant component in only a few, such as cocoa butter and shea

butter. It is also present in most animal fats and is a major component

in the tallow of ruminant fats.

Very-long-chain fatty acids: those with 21 or more carbon atoms e.g.

Behenic acid (22: 0) and lignoceric acid (24: 0)

17

Table 2.2: Commonly used Fatty Acid Nomenclature Systems

System Example Explanation

Trivial

nomenclature Palmitoleic acid

Trivial names (or common names) are non-systematic

historical names, which are the most frequent naming

system used in literature. Most common fatty acids have

trivial names in addition to their systematic names.

These names frequently do not follow any pattern, but

they are concise and often unambiguous.

Systematic

nomenclature

(9Z)-octadecenoic

acid

Systematic names (or IUPAC names) derive from the

standard IUPAC Rules for the Nomenclature of Organic

Chemistry (Rigaudy, 1979) published along with a

recommendation published specifically for lipids (The

Nomenclature of Lipids, Recommendations, 1977).

Counting begins from the carboxylic acid end. Double

bonds are labeled with cis-/trans- notation or E-/Z-

notation, where appropriate. This notation is generally

more verbose than common nomenclature, but has the

advantage of being more technically clear and

descriptive.

Δx nomenclature

cis,cis-

Δ9,Δ

12octadecadienoic

acid

In Δx (or delta-x) nomenclature, each double bond is

indicated by Δx, where the double bond is located on

the xth

carbon–carbon bond, counting from the

carboxylic acid end. Each double bond is preceded by

a cis- or trans- prefix, indicating the conformation of the

molecule around the bond. e.g. linoleic acid is

designated "cis-Δ9, cis-Δ

12 octadecadienoic acid". This

nomenclature has the advantage of being less verbose

than systematic nomenclature, but is no more technically

clear or descriptive.

n - x nomenclature n - 3

n−x (n minus x, ω−x or omega-x) nomenclature

provides names for individual compounds and classifies

them by their likely biosynthetic properties in animals. A

double bond is located on the xth

carbon–carbon bond,

counting from the terminal methyl carbon (designated

as n or ω) toward the carbonyl carbon. e.g α-Linolenic

acid is classified as a n−3 or omega-3 fatty acid, and so

it is likely to share a biosynthetic pathway with other

compounds of this type. It is common in nutritional

literature, but IUPAC has deprecated it in favor

of n−x notation in technical documents (Rigaudy, 1979).

Lipid numbers

18:3

18:3, n - 6

18:3, cis,cis,cis-

Δ9,Δ

12,Δ

15

Lipid numbers take the form C:D, where C is the

number of carbon atoms in the fatty acid and D is the

number of double bonds in the fatty acid. This notation

can be ambiguous, as some different fatty acids can have

the same numbers. Consequently, when ambiguity exists

this notation is usually paired with either a Δx or

n−x term (Rigaudy, 1979)

18

Table 2.3: Common saturated fatty acids in food fats and oils

(FAO, 2008)

Trivial name Systematic name

Abbreviation Typical sources

Butyric acid Butanoic acid C4:0 Dairy fat

Caproic acid Hexanoic acid C6:0 Dairy fat

Caprylic acid Octanoic acid C8:0 Dairy fat, coconut and palm

kernel oils

Capric acid Decanoic acid C10:0 Dairy fat, coconut and palm

kernel oils

Lauric acid Dodecanoic acid C12:0 Coconut oil, palm kernel oil

Myristic acid Tetradecanoic

acid C14:0

Dairy fat, coconut oil, palm

kernel oil

Palmitic acid Hexadecanoic

acid C16:0 Most fats and oils

Stearic acid Octadecanoic acid C18:0 Most fats and oils

Arachidic acid Eicosanoic acid C20:0 Peanut oil

Behenic acid Docosanoic acid C22:0 Peanut oil

Lignoceric

acid

Tetracosanoic

acid C24:0 Peanut oil

Unsaturated Fatty Acids contain one or more double bonds (carbon-to-

carbon)and are found mostly in plants and sea food. Because of the

presence of double bonds, unsaturated fatty acids are chemically more

reactive than SFAs and their reactivity increases as the number of double

bonds increases. As per the FAO/WHO Expert Consultation, unsaturated

fatty acids are classified as:

• Short-chain unsaturated fatty acids: fatty acids with ≤ 19 carbon atoms.

• Long-chain unsaturated fatty acids: fatty acids with 20-24 carbon atoms.

• Very-long unsaturated chain fatty acids: fatty acids with ≥ 25 carbon

atoms.

Further, based on the extent of unsaturation, unsaturated fatty acids (UFA) are

categorized MUFAs and PUFAs and based on the placement of hydrogen on the

double bond they are classified as Cis or Trans isomers.

Cis-Monounsaturated Fatty Acids

Fatty acids containing one double bond are called Monounsaturated Fatty

Acids (MUFA). In general, they have an even number of carbon atoms,

19

between C14 to C24, and the double bond is most likely located at the 9th

position (Table 2.4). Oleic acid (cis-9-octadecenoic acid or 9c-18:1) is the

most frequently occurring cis -MUFA and is also the most widely

distributed of all the natural fatty acids. The other cis -MUFAs though

widely distributed in plants and animal tissues, are very often minor

components of the human diets. Palmitoleic acid (9c-16:1) is the most

widely occurring hexadecenoic acid. It is a minor component in most

animal and vegetable oils, but more significant in marine oils (around

10%), and it is a major component in a few seed oils (e.g. macadamia oil).

C22:1 acid (Erucic acid; 13- cis -docosenoic acid or 22:1n–9) occurs

generally in higher amounts in seed oils of Brassicaceae family, reaching a

level of 40-60% in mustard seed oil and high-erucic acid rapeseed oil.

These oils are consumed in some parts of Asia (particularly India) and

Eastern Europe. MUFAs with more than 22 carbon atoms are rare in

human diets, except for 15c-24:1 which is present as a minor component in

many marine oils.

Polyunsaturated Fatty Acids

Fatty acids containing more than one double bond are called

Polyunsaturated Fatty Acids (PUFA). Natural PUFAs with methylene-

interrupted double bonds and with all cis configuration can be divided

into12 different families ranging from double bonds located from the n–1

to n–12 positions countered from the methyl end (Gunstone, 1999). The

most important families, in terms of human health and nutrition include the

n-6 and n-3.All members of the n-6 family of fatty acids contain their first

double bond between the sixth and seventh carbon atoms from the terminal

methyl group, while all members of the n-3 family of fatty acids have their

first double bond between the third and fourth carbon atoms. Linoleic acid

(LA) is the parent fatty acid of the n-6 family, while α linolenic acid

(ALA) is the parent fatty acid of the n-3 family with both containing 18

carbon atoms. Both LA and ALA series are essential fatty acid (EFA) and

20

can be desaturated and elongated in humans to form a series of n-6 (Lin

series) and n-3 (Lan series) PUFA respectively (Table 2.5).

Table 2.4: Some common cis-monounsaturated fatty acids in fats and oils

(FAO, 2008)

Common name Systematic

Name

Delta

Abbreviation Typical sources

Palmitoleic acid cis-9-

hexadecenoic

acid

16:1Δ9c

(9c-16:1)

Marine oils, macadamia

oil, most animal and

vegetable oils.

Oleic acid cis-9-

octadecenoic

acid

18:1Δ9c

(9c-18:1)

All fats and oils, especially

olive oil, canola oil and

high-oleic sunflower and

safflower oil

Cis-vacceni acid

cis-11-

octadecenoic

acid

18:1Δ11c

(11c-18:1) Most vegetable oils

Gadoleic acid cis-9-eicosenoic

acid

20:1Δ9c

(9c-20:1) Marine oils

Eicosenoic acid cis-11-

eicosenoic acid

20:1Δ11c

(11c-20:1) Marine oils

Erucic acid cis-13-

docosenoic acid

22:1Δ13c

(13c-22:1)

Mustard seed oil, high

erucic acid rapeseed oil

Nervonic acid

cis-15-

tetracosenoic

acid

24:1Δ15c

(15c-24:1) Marine oils

Essential Fatty Acids (EFA)

Essential fatty acids (EFA) are those fatty acids, which the human body

cannot synthesize and therefore, they must be supplied through diet.

EFAs are long-chain unsaturated fatty acids derived from α-linolenic

(Omega-3) and linoleic acids (Omega-6). Oleic acids an Omega-9 MUFA

is necessary yet “non-essential” because the body can synthesize a modest

amount of this fatty acid, provided the other essential fatty acids are

present.

21

EFA deficiency is linked with serious health conditions such as heart

attacks, stroke, cancer, insulin resistance, obesity, diabetes, arthritis,

asthma, lupus, schizophrenia, depression/ postpartum depression,

accelerated aging, attention deficit hyperactivity disorder (ADHD) and

alzheimer’s disease among others (Simpoulos, 1999).Arachidonic acid

(AA) is the most important n-6 PUFA because it is the primary precursor

for the n-6 derived eicosanoids (Table 2.5). It is present, though in low

amounts in meat, eggs, fish, algae and other aquatic plants (Wood et al,

2008; Ackman, 2008). Eiocosapentaenoic acid (EPA) and

docosahexaenoic acid (DHA) on the other hand are the most important n-3

fatty acids in human nutrition.

EPA and DHA are components of marine lipids. Highly specialized

membranes such as synaptic terminals, retinal cells and heart myocytes,

contain very high amounts of AA (20:4 n-6) and DHA (22: 6 n-3). These

EFA are components of phospholipids, mainly the structural lipids (in

highly fluid membranes, contractile cells, and muscular cells) and play

functional roles (e.g. receptor functions, ion channels, neurotransmitter

release). While the AA is in turn converted to hormone-like substances

called eicosanoids including prostaglandins (PGs), thromboxanes (TXs),

prostacyclins, and lipoxins; while DHA is converted to docosanoids. The

eicosanoids and docosanoids play important roles in the regulation of

widely diverse physiological functions, including blood pressure, platelet

aggregation, blood clotting, blood lipid profiles, the immune response and

the inflammation response to injury/ infection.

LA occurs in almost all dietary fats and attains major proportions in most

vegetable oils (White, 2009). ALA is primarily present in plants, occurring

in high concentrations in some seeds and nuts and also in some vegetable

oils, although its presence in conventional diets is much lower than that of

LA. Marine fish such as mackerel, salmon, sardine, herring and smelt are

excellent sources of EPA and DHA (Ackman, 2008).

22

Conjugated Linoleic Acid

Small amounts of positional and geometrical isomers of LA, having two

conjugated double bonds, are also present in the human diet, primarily

derived from ruminant fats. Conjugated linoleic acids (CLA) are a family

of at least 28 isomers of linoleic acid found mainly in the meat and dairy

products of ruminant animals.

As the name implies, the double bonds of CLA are said to be conjugated

as there is only one single bond between the two double bonds.

Conjugated linoleic acid can occur both in a cis and a trans configuration.

The cis bond causes a lower melting point and ostensibly also the observed

beneficial health effects. Unlike other trans fatty acids, the trans CLA may

have beneficial effects on human health. CLA are produced by

microorganisms in the rumen of ruminants as a result of biohydrogenation

of dietary LA. Non-ruminants, including humans, produce certain isomers

of CLA from trans isomers of oleic acid, such as vaccenic acid, which is

converted to CLA by delta-9-desaturase (Kuhnt et al, 2006). More recent

studies using individual isomers indicate that the two isomers c9,t11-CLA

and t10,c12-CLAhave very different health effects (Tricon et al, 2004).

The CLA levels in dairy fats usually range from 0.3–0.6% of total fat

(Parodi, 2003). The beneficial functions of CLA include its antimutagenic,

anticarcinogenic and antiobesity properties as well as its effects on

regulating lipid metabolism and immune response. In view of the health

benefits of trans isomers, in the United States, trans linkages in a

conjugated system are not counted as trans fatty acids for the purposes of

nutritional regulations and labeling.

23

Table 2.5: Nutritionally Important n-3 and n-6 PUFA

(FAO, 2008)

Common name Systematic name N minus

abbreviation Typical sources

Nutritionally important n-3 PUFA

α-linolenic acid cis-9,cis-12, cis-15-

octadecatrienoic

acid

18:3n-3

(ALA)

Flaxseed oil, perilla

oil, canola oil,

soybean oil

Stearidonic acid

cis-6,cis-9,cis-

12,cis-15-

octadecatetraenoic

acid

18:4n-3

(SDA)

Fish oils, genetically

enhanced soybean oil,

blackcurrant seed oil,

hemp oil

Eicosatetraenoic

acid

cis-8,cis-11,cis-

14,cis-17-

eicosatetraenoic

acid

20:4n-3 Very minor

component in animal

tissues

Eicosapentaenoic

acid

cis-5, cis-8,cis-

11,cis-14,cis-17-

eicosapentaenoic

acid

20:5n-3

(EPA)

Fish, especially oily

fish (salmon, herring,

anchovy, smelt and

mackerel)

Docosapentaenoic

acid

cis-7,cis-10,cis-

13,cis-16, cis-19-

docosapentaenoic

acid

22:5n-3 (DPA)

Fish, especially oily

fish (salmon, herring,

anchovy, smelt and

mackerel)

Docosahexaenoic

acid

cis-4,cis-7,cis-

10,cis-13,cis-16,cis-

19-docosahexaenoic

acid

22:6n-3

(DHA)

Fish, especially oily

fish (salmon, herring,

anchovy, smelt and

mackerel)

Nutritionally important n-6 PUFA

Linoleic acid cis-9,cis-12-

octadecadienoic 18:2n-6 (LA) most vegetable oils

γ-linolenic acid cis-6, cis-9,cis-12-

octadecatrienoic

acid

18:3n-6

(GLA)

Evening primrose,

borage and

blackcurrant seed oils

Dihomo-γ-

linolenic acid cis-8,cis-11,cis-14-

eicosatrienoic acid 20:3n-6

(DHGLA)

Very minor

component in animal

tissues

Arachidonic acid

cis-5,cis-8,cis-

11,cis-14-

eicosatetraenoic

acid

20:4n-6 (AA) Animal fats, liver, egg

lipids, fish

Docosatetraenoic

acid

cis-7,cis-10,cis-

13,cis-16-

docosatetrtaenoic

acid

22:4n-6 Very minor

component in animal

tissues

Docosapentaenoic

acid

cis-4,cis-7,cis-

10,cis-13,cis-16-

docosapentaenoic

acid

22:5n-6 Very minor

component in animal

tissues

24

2.2 TRANS FATTY ACIDS AND THEIR FORMATION

The double bonds of most naturally occurring unsaturated fatty acids in food fats

are in the cis configuration, however, double bonds in the trans configuration do

occur in nature. In chemical terms, trans fatty acid refers to a lipid molecule that

contains one or more double bonds in trans geometric configuration. In trans

configuration, the carbon chain extends from opposite sides of the double bond,

rendering a straighter molecule, whereas, in cis configuration, the carbon chain

extends from the same side of the double bond, rendering a bent molecule (Figure

2.2).

Small amounts (2-6%) of trans fatty acids are naturally present in ruminant

deposits and milk fats (Huth, 2007). Trans fatty acids arise in the stomach of

ruminants as a result of the hydrogenation of dietary unsaturated fatty acids during

bacterial fermentation. Human diets contain not only natural trans fatty acids, but

also those arising from technological treatments, such as partial hydrogenation of

Trans Fatty Acids (TFAs) are unsaturated fatty acids that contain at least one

non-conjugated double bond in the trans configuration, i.e. the hydrogen on the

doubly bonded carbon atoms is in the trans configuration, resulting in a straighter

shape (Mozaffarian et al, 2006).

In the Codex Alimentarius, trans fat to be labeled as such is defined as “the

geometrical isomers of monounsaturated and polyunsaturated fatty acids having

non-conjugated [i.e. interrupted by at least one methylene group (-CH2-CH2-)]

carbon-carbon double bonds in the trans configuration”. This definition excludes

specifically the healthy 'trans fats' (vaccenic acid and conjugated linoleic acid)

which are present especially in human milk, dairy products, and beef (FAO/WHO,

2007).Trans fatty acids can be defined as the sum of all isomeric fatty acids with

14, 16, 18, 20 and 22 carbon atoms and one or more trans double bonds, i.e.

C14:1, C16:1, C18:1, C18:2, C18:3, C20:1, C20:2, C22:1, C22:2 trans isomeric

fatty acids.

TFA are less fluid and have a higher melting point than the corresponding cis fatty

acids and include both monounsaturated and Polyunsaturated trans fatty acids,

having either all unsaturations in the trans form or some in trans and other in cis

form (Martin et al, 2007).

25

oils to produce fat blends for margarine, shortening and deep fat frying (Craig-

Schmidt and Teodorescu, 2008).

Partially hydrogenated vegetable and marine oils constitute the main source of

trans fatty acids in human diets in some parts of the world. Trans fatty acids

derived from partial hydrogenation are often referred to as industrial trans fatty

acids (I-TFA). Trans fatty acids are also formed inadvertently during the refining

process of vegetable oils (Ackman et al, 1974). As a result, refined vegetable oils

can contain small amounts (~2%) of trans fatty acids (Ratnayake and Zehaluk,

2005). Both, bio-hydrogenation and industrial partial hydrogenation result in

isomerization of naturally occurring cis unsaturated fatty acids to trans isomers

as well as positional isomers. Thus, partial hydrogenation results in the formation

of an assortment of new cis and trans isomers of MUFA and PUFA. In ruminant

fats and partially hydrogenated vegetable oils, the trans-octadecenoic acid (trans-

oleic or trans-18:1) isomers are the most important group of trans fatty acids. The

position of the double bond of these dietary trans 18:1 isomers, counted from the

carboxylic carbon, usually varies from ∆4 to ∆ 16. The trans 18:1 isomer

distribution in partially hydrogenated vegetable oils depends on the fatty acid

composition of the starting oil, the extent of hydrogenation and very often the

trans 18:1 isomers form a Gaussian distribution that centers around the ∆ 9 or ∆

10 double bond (Ratnayake, 2004).The trans 18:1 isomer distribution of dairy fats

is distinctly different from that of partially hydrogenated vegetable oils. Vaccenic

acid (11t-18:1) is always the major isomer in ruminant fats (30–60% of total t-

18:1), whereas 9t-18:1 and 10t-18:1 isomers occur in relatively low amounts. In

addition to the trans 18: 1 isomers, partially hydrogenated oils contain several cis-

octadecenoic isomers (cis-18:1), wherein double bond position generally ranges

from 6 to 16 (Ratnayake, 2004; Parodi, 1976; Mendis et al, 2008).

Dietary fats also contain a number of positional and geometrical isomers of LA

and ALA which are frequently present in low concentrations in both partially

hydrogenated and non-hydrogenated dietary fats (Ratnayake, 2004). Partially

hydrogenated vegetable oils contain 15 or more isomers of LAs; the major ones

26

being 9c, 12t-18:2 and 9t, 12c-18:2. These isomers are often detected in large

quantities in mildly hydrogenated vegetable oils (up to 6% of total fatty acids),

whereas they are hardly detectable in heavily hydrogenated oils. The LA and ALA

isomers present in non-hydrogenated fats or in many common food fats are the

result of exposure of these PUFAs to some form of heat treatment, such as steam

deodorization or stripping during refining of oils or simple heating in deep fat

frying (Grandgirard, 1994; Ackman et al, 1974). In these processes, the double

bonds do not shift in position, but are isomerized from cis to trans, resulting in the

formation of small amounts of geometric trans isomers of LA and ALA.

2.2.1 History of Trans Fatty Acid

The history of trans fatty acids, dates back to 19th

century. Trans fatty acid

containing partially hydrogenated fat, became popular with consumers and food

manufacturers because it acted as a preservative, giving foods a longer shelf life

(Katan, 2008). It also gave foods a more tempting taste and texture. The

hydrogenation process was first discovered around the turn of the 20th

century,

making it possible to produce partially hydrogenated fat. It was the first man-

made fat to join the food supply.

The synthesis of hydrogenated compounds originated in the 1890s, when French

chemist Paul Sabatier discovered that metal catalysts could be used to precipitate

hydrogenation reactions (for the discoveries concerning catalysts, Paul Sabatier,

shared the 1912 Nobel Prize for Chemistry with French chemist Victor Grignard).

In 1901, German chemist Wilhelm Normann experimented with hydrogenation

catalysts and successfully induced hydrogenation of liquid fat, producing

semisolid fat, which came to be known as trans fatty acids (Eckel et al, 2007).

This process, for which Normann received a patent in 1903, was adopted by food

manufacturers. Products containing unsaturated fats were susceptible to rancidity

upon exposure to air, resulting in a short shelf life (Table 2.6). Therefore, a stable

form of unsaturated fat had the potential to significantly extend the shelf life and

value of a variety of foods. Hydrogenation was important particularly in the

production of margarine, which was used in place of butter when the latter was

27

rationed during World War II (Schleifer, 2012). In the following decades, the use

of hydrogenation to stabilize the shelf life of food products grew rapidly. The first

food product developed that contained trans fatty acids was “Crisco” vegetable

shortening, introduced in 1911 by Procter & Gamble Company. By the 1980s,

many food manufacturers in the western countries had stopped using tallow and

lard, replacing these fats with trans-fat based products, which had similar smoke

points and were thought to be healthier. In India, the partially hydrogenation of

vegetable oil (PHVO) was introduced in 1960s and marketed under the brand

name “vanaspati” (Ghafoorunissa, 2008).

Table 2.6: Landmarks in the History of Trans fatty Acids

Year Developments

1890s French chemist Paul Sabatier developed the hydrogenation process. He

became a Nobel laureate in 1912.

1902 German chemist, scientist, Wilhelm Normann established that liquid oils

can be hydrogenated to form semi-solid fats (trans fatty acids) and got

the process patented. Trans fat became the first man-made fat to join the

food supply.

1911 Procter & Gamble introduced Crisco vegetable shortening in grocery

stores. Crisco became the first food product containing trans fatty acids.

1937 During the second World War, the use of margarine escalated due to the

rationing of butter.

1957 The American Heart Association for the first time proposed that

reducing dietary fats, namely saturated fats found in foods like butter

and beef, can reduce the chances of getting heart diseases.

1960 In India, the partially hydrogenation of vegetable oil (PHVO) was

introduced which was marketed under the brand name “vanaspati”.

1984 Consumer advocacy groups campaigned against using saturated fat

(SFA) for frying in fast-food restaurants. In response, most fast-food

companies began using partially hydrogenated oils containing trans fatty

acids instead of beef tallow and tropical oils high in saturated fats.

1993 Following the release of several scientific studies, health advocacy

groups called for fast-food restaurants to stop using partially

hydrogenated oils in their deep fryers.

1999 The U.S. government proposed a law requiring food manufacturers to

list trans fatty acids amounts on nutrition labels. The proposal was

however, not passed as law.

28

2002 The government agreed with researchers for the first time on record that

there was likely no safe level of trans fat and that people should eat as

little of TFA as possible.

2003 Denmark became the first country to regulate trans fatty acids

consumption on a national basis, putting a very small cap on the amount

of TFA that the food may contain. Later in 2003, the U.S. Food and

Drug Administration (U.S. FDA) passed a law requiring trans fatty acids

to be listed on the Nutrition Facts label on food products; food

manufacturers were given three years to comply. Many reformulated

their products to limit TFA.

2006 Trans fat labeling became mandatory in the United States. The

American Heart Association was the first major health organization to

specify a daily limit: less than 1 percent of calories from trans fatty

acids. Later in the year, New York became the first U.S. city to pass a

regulation limiting trans fatty acids in restaurants. Multiple cities and

states have since proposed similar regulations.

2007 To put trans fatty acids into the context of the overall “big fat picture,”

and help consumers better understand fats and their impact on health,

the American Heart Association launches its “Face the Fats” consumer

education campaign.

January,

2010

Food Safety and Standards Authority of India (FSSAI) organized

“National Consultation on the Proposed Trans Fat Regulation” at NIN

May,

2010

The Food Safety and Standards Authority of India (FSSAI) ask for

comments from stakeholders and the public on the “Revised Draft

Regulation of Trans Fatty Acids (TFAs) in Partially Hydrogenated

Vegetable Oils, PHVOs”. The FSSAI, through the

proposed draft notification, intends to change the limit level of TFA in

PHVO from 10% to 5% within three years. The proposed limit is based

on the recommendations given by National Institute of Nutrition,

Hyderabad.

2010 National Dietary Guidelines Consensus Group formulated the

Consensus dietary guidelines for healthy living and prevention of

obesity, the metabolic syndrome, diabetes, and related disorders in

Asian Indians and recommended that TFAs should be <1% of total

energy/day. (Misra et al, 2011)

2010 The Expert Group of the Indian Council of Medical Research released

the Nutrient requirements and recommended dietary allowances for

Indians, with recommendation in line with FAO/ WHO that TFAs

should be <1% of total energy/day. (ICMR, 2010)

2011 In the revised draft recommended dietary allowances by NIN/ ICMR in

2011, it was recommended that the intake of trans fatty acids should not

exceed 2% of energy (NIN/ ICMR, 2011)

29

Later during the 1990s numerous research studies were conducted, revealing

correlation between the trans fatty acids intake and increased LDL (bad)

cholesterol levels and a higher incidence of heart diseases. Around this time

nutrition labels became a hotly debated topic. Scientists and food manufacturers

argued over whether it is required to separately list the trans fatty acid content on

food packages (Katan, 2008). Table 2.6 briefly summarizes the landmarks in the

history of Trans fatty acids.

2.2.2 Biochemistry of Trans Fatty Acids

TFA are formed in large amounts during artificial processing of vegetable oils

while some amount of TFA exists naturally in dairy products and meats.

Depending on the position of the double bond, several positional isomers are

possible. During partial hydrogenation of vegetable oils, the cis double bonds

present in the fatty acids are converted into trans configuration. This change in

configuration completely alters the physical property of the vegetable oils. The cis

configuration induces a characteristic “U” shaped bend in the acyl chain and

therefore they are less tightly packed and exist as liquid at room temperature due

to lower melting point. Compared to cis, trans configuration has more rigid

structure similar to saturated fatty acids and are tightly packed. Therefore, the

fatty acids in trans configuration exist as solid at room temperature due to high

melting point. Thus, TFA are less fluid and have a higher melting point than the

corresponding cis fatty acids. These class include monounsaturated trans fatty

acids (MTFA), and Polyunsaturated trans fatty acids (PTFA), having either all

unsaturations in the trans form or some in trans form and other in cis form (Wolff,

1992).

2.2.3 Formation and Types of Trans Fatty Acids

Among the processes resulting in TFA formation, hydrogenation of vegetable oils

stands out for its impact on the diet of populations in industrialized countries.

Other processes such as thermal treatments including edible oil refining, meat

irradiation, frying, and bio-hydrogenation also contribute to the dietary intake of

TFA (Martin et al, 2007). Trans fatty acids present in our diet can be naturally

30

occurring/ Ruminant Trans Fatty Acids (N-TFAs) and/ or industrially produced

Trans Fatty Acids (I-TFAs) which are produced during partial hydrogenation and

thermal treatments of oils.

Figure 2.2: Structure of Trans, Cis and Saturated fatty acids

(Source: http://en.wikipedia.org/wiki/Trans_fat)

2.2.3.1 Natural/ Ruminant Trans Fatty Acids: Some TFAs are found naturally

in small amount in ruminant animals and their products like various meat and

dairy products. In animals belonging to the Ruminantia suborder, the action of

microorganisms present in the rumen (Butyrivibrio fibrisolvens and Megasphaera

elsdenii) leads to isomerization of polyunsaturated fatty acids, resulting in

formation of conjugated linolenic acid (18:2 9c, 11t ) and vaccenic acid (18:2 10t,

12c) (Bauman et al, 1999). The effects observed for acids 18:2 9c, 11t and that of

18:2 10t, 12c are distinct from those of the other TFA. Isomer 9c, 11t seems to

have physiological importance as an antioxidant and in the inhibition of several

forms of neoplasias as demonstrated in animal studies (Martin et al, 2007). On the

other hand, the observed effect of the isomer 18:2 10t, 12c on the metabolism of

lipids is important, as this trans fatty acid is capable of generating favorable body

composition changes in some people.

Cis Configuration Trans Configuration Saturated fatty acid

Oleic acid is a cis unsaturated

fatty acid that comprises 55–

80% of olive oil (Alonso et al,

1999).

Elaidic acid is the

principaltransunsaturated fatty acid

found in partially hydrogenated

vegetable oils (Thomas, 2002).

Stearic acid is a saturated fatty

acid found in animal fats

(Thomas, 2002).

Melting Point: 13.4oC Melting Point: 45

oC Melting Point: 66.9

oC

31

Table 2.7: Trans Fatty Acids: Major Isomers with their Sources

(Bhardwaj et al, 2011a)

Trans Fatty

Acid

Process % of

Trans

Fatty

Acid

Major Isomer Sources

Natural/

Ruminant

Trans Fatty

Acid

Bio-

hydrogenatio

n

3-8%

18:1 Δ11t

(Vaccenic acid)

Conjugated

linolenic acid

(CLA; 0.5 -

2%)

Milk, Meat,

Dairy Products

Industrially

produced

Trans Fatty

Acid

Partial

Hydrogenatio

n of

Vegetable

Oils

10 - 50

%

18:1 t (Elaidic

acid, 18:1Δ9t)

(80-95%)

Others

include18:2,

18:3 & 16:1

trans isomers

Vanaspati,

Margarine

Thermal

Treatments

(Deodorizatio

n, cooking &

frying)

1-3 % 18:2 & 18:3

trans isomers

Refined

Vegetable oil,

fried food items

prepared in re-

heated/ re-used

oil

The trans fatty acid content of ruminant products can be changed to some degree

by altering the animals’ feed, although levels of trans fat in milk and meats are

already relatively low ranging from 1 to 8 percent of total fats (Lock and

Bauman, 2004). In fact, most efforts have focused on increasing, rather than

decreasing, the levels of conjugated linolenic acid in ruminant products, owing to

its hypothesized health benefits for humans. However, the evidence of such

benefits is inconclusive. For example, dietary trials indicate that consumption of

conjugated linolenic acid (CLA) reduces insulin sensitivity, increases lipid

peroxidation, and has mixed effects on markers of inflammation and immune

function (Riserus et al, 2004). Of four prospective studies evaluating the relation

between the intake of trans fatty acids from ruminants and the risk of CHD, none

identified a significant positive association, whereas three identified non-

significant trends toward an inverse association (Jakobsen et al, 2008; Oomen et

al, 2001). Another review on the quantitative comparison of the effect of

32

ruminant trans fatty acids and CLA with that of industrial trans fatty acids on

blood lipoproteins in humans indicated that all three classes of trans fatty acids

raise the ratio of LDL to HDL, and therefore, presumably, the risk of coronary

heart disease (Figure 2.3, 2.4. 2.5). The effect of ruminant trans fatty acids and

CLA on the LDL to HDL ratio was less than that of industrial trans fatty acids

although the difference was not significant. However, more studies are needed to

decide whether this difference is real or due to chance (Brouwer et al, 2010). The

absence of concrete evidence of a higher risk of CHD associated with the intake

of trans fatty acids from ruminants as compared to the industrially produced TFA

may be due to lower levels of ruminant TFA intake (typically less than 0.5

percent of total energy intake), different biological effects (ruminant and

industrial trans fatty acids share some, but not all, isomers), or the presence of

other factors in dairy and meat products that balance any effects of the small

amount of TFA, if any.

33

Figure 2.3 Results of randomized studies of the effects of diets high in

industrial trans fatty acids, ruminant trans fatty acids and CLA compared

with cis-unsaturated fatty acids on the ratio of LDL- to HDL-cholesterol.

Source: Brouwer et al, 2010

2.2.3.2 Industrially Produced Trans Fatty Acids (I-TFAs) result from the

industrial processes such as hydrogenation of vegetable oils and thermal

treatments such as refining of vegetable oils, frying of foods and food irradiation.

Figure 2.4Results of randomized studies of

the effects of diets high in industrial trans

fatty acids, ruminant trans fatty acids, CLA

compared with cis-unsaturated fatty acids on

LDL cholesterol.

Figure 2.5 Results of randomized studies of

the effects of diets high in industrial trans

fatty acids, ruminant trans fatty acids, CLA

compared with cis-unsaturated fatty acids

on HDL cholesterol.

34

Hydrogenation of Vegetable Oils: TFAs are mainly produced when the oil

is converted to solid fat through a chemical process – hydrogenation,

wherein hydrogen is added to unsaturated fatty acids in vegetable oil(s).

This changes the fat from a liquid to a soft/solid state simultaneously

generating TFAs (Mozaffarian et al, 2006). The TFA content of the

hydrogenated fat varies from 10-40%. Several factors such as

polyunsaturated fatty acid (PUFA) composition of the native oil, type of

catalyst used and the hydrogenation conditions such as temperature and

pressure determine the trans fatty acid level and the type of trans isomer.

The major trans isomer present in the partially hydrogenated vegetable oil

is 18:1t (80-90%) isomer. Among the 18:1t isomer, elaidic acid (18:1 ∆9 t)

is the major trans isomer (85- 90%). Other trans isomers include 16:1t,

18:2t and 18:3t.

Partially hydrogenated vegetable oils can replace naturally solid, saturate-

rich fats (such as Desi Ghee, butter, lard etc.) in baked/fried foods, Indian

sweets as well as in commercial frying where vegetable oils cannot be

used. These fats are preferred by commercial food processors as they

accord a longer shelf life and impart desirable taste, shape, and texture to

the food; they are also used in baked products or are formed in the foods

while frying. The production of high TFA containing fats was considered

important for many decades by the hydrogenation industry not only to

increase shelf life, but also mainly to improve the physical, chemical, and

organoleptic characteristics of fats (Johnson, 1998).

Thermal Treatments: The thermal processes causing the formation of

trans fatty acids include refining of vegetable oils, frying of food and food

irradiation.

Refining of Vegetable Oils: Due to the exposure to high temperature,

small amount of TFA are also reportedly formed during the refining of

vegetable oils. Edible oils are subjected to refining in order to remove

certain impurities/ naturally present attributes (free fatty acids,

phospholipids, carbohydrates, and proteins as well as their degradation by-

35

products; water, chlorophyll, carotenoids, and fatty acid oxidation

products) which may alter the color, taste, and aroma. Such substances can

often restrict the application of oil, and reduce their shelf life. Refining

generally includes degumming, neutralization, bleaching, and

deodorization.

During refining, the vegetable oils are commonly heated between 60◦C and

100◦C; and then subjected to deodorization, which aims to improve oil’s

organoleptic characteristics by removing oil solvents used during the

process of extraction as well as low molecular weight compounds naturally

present in the oil. During deodorization process, the temperature is raised

(180 to 270ºC) which leads to formation of TFA in the vegetable oil

(Bhardwaj et al, 2011a). Double bonds in the fatty acids of vegetable oils

subjected to the high temperatures during refining, especially the

deodorization process, undergo geometrical isomerization from the cis to

trans configuration. Oleic acid is hardly affected, while α-linolenic acid

has a greater tendency to isomerization even than linoleic acid. The two

possible mono-trans isomers of linoleic acid (i.e. 9c, 12t-18:2 and 9t, 12c-

18:2) are formed in roughly equal amounts, while the all-trans isomer (9t,

12t-18:2) is produced at a much lower concentration (Moreno et al, 1999).

Frying of Food: Frying is one of the oldest and popular methods of food

preparations. Fried foods have a characteristic flavour, colour, and crispy

texture, which make deep-fat fried foods very popular among the

consumers. Frying is the process of immersing food in hot oil allowing a

close contact between air and food at high temperatures of nearly 150ºC to

190ºC or more. The simultaneous heat and mass transfer of oil, food and

air during deep-fat frying produces the desirable and unique quality of

fried foods; the frying oil acts as a heat transfer medium and contributes to

the texture and flavour of the fried food. During deep fat frying, edible

oils/fats undergo various chemical reactions which include oxidation,

hydrolysis, isomerization, polymerization and cyclization. As a result, a

36

multitude of products like free fatty acids, trans fatty acids, mono and

diacylglycerols, oxidized monomers, dimers and polymers are formed. At

the high temperatures of frying, thermal reactions occur, giving rise to

cyclic monomers, dimers and polymers (Goyal and Sundararaj, 2009). As

a result of these reactions several physical and chemical changes also

occur in the oil, producing numberless substances that are incorporated

into foods and which alter their appearance, aroma, and taste (Moreno et

al, 1999). Foods fried in deteriorated oil/fat absorb these products, many of

which are potentially toxic on consumption.

During food frying, formation of TFA is closely related to the processing

temperature and the oil use time (Moreno et al, 1999). Double bonds in the

fatty acids of vegetable oils subjected to the high temperatures during

frying, can also undergo geometrical isomerization from the cis to trans

configuration. Further, when instead of oils partially hydrogenated fats are

used, due to their comparatively lesser unsaturation the formation of TFA

is generally lower; however, their initially high TFA content results in a

larger concentration of trans isomers in the fried food. Several European

countries have specified that the frying oil temperature must not exceed

180◦C. In France, it has been established that the oil commercially used in

frying must contain at the most 3% alpha-linolenic acid (Wolff, 2002).

These measures not only help to decreased degradation of unsaturated fatty

acids but also result in a lower level of mono or poly trans fatty acids

(MTFA and PTFA) formation.

Food Irradiation: It is a form of food processing to extend the shelf life

and reduce the spoilage of the food (Minami et al, 2012). The use of

irradiation technology in food preservation has raised interest mainly due

to its efficiency and its multiple possible applications. Irradiation of meat

increases its shelf life by protecting it from pathogenic microorganisms;

however, it also produces structural changes in many nutrients, which may

have adverse consequences on nutritional value of foods. The free radicals

formed by irradiation of unsaturated fatty acids react with them leading to

37

the formation of carbonyl compounds, which are responsible for associated

changes in the nutritional and organoleptic characteristics of food (Martin

et al, 2007). Furthermore, breaking of the double bonds favours the

formation of TFA as its conversion in the trans configuration reduces the

free energy of the fatty acid. Minami et al (2012) examined the effects of γ

irradiation on the fatty acid composition, lipid peroxidation level, and

antioxidative activity of soybean and soybean oil. The results indicated

that irradiation at 10 to 80 kGy under aerobic conditions did not markedly

change the fatty acid composition of soybean, while 10-kGy irradiation did

not markedly affect the fatty acid composition of soybean oil under either

aerobic or anaerobic conditions. However, 40-kGy irradiation considerably

altered the fatty acid composition of soybean oil under aerobic conditions.

Further, 40-kGy irradiation produced a significant amount of trans fatty

acids under aerobic conditions. Irradiating soybean oil induced lipid

peroxidation and reduced the radical scavenging activity under aerobic

conditions, but had no effect under anaerobic conditions. These results

indicate that the fatty acid composition of soybean was not markedly

affected by radiation at 10 kGy, and that anaerobic conditions reduced the

degradation of soybean oil that occurred with high doses of γ radiation.

There are many controversies on appropriate doses for food irradiation.

Countries such as the United States and Canada have established that for

the red meat group, irradiation of fresh food must not exceed 4.5 kGy

(Kilogrey) while in England up to 7.0 kGy, and in South Africa upto 45

kGy is permitted (FDR, 2002).

2.2.4 Dietary Sources of Trans Fatty Acids

In developed countries some quality data on TFA content of various food items

do exist (Table 2.8). However, in India not much work has been done regarding

laboratory analysis of TFA content of commonly consumed food articles.

Therefore, Misra et al, (2009a) have reported TFA content of certain commonly

consumed food articles (Table 2.9) based on the levels of TFA content from

studies by Ghafoorunisa and Krishnaswamy (1994).

38

Table 2.8: Dietary Sources of TFA

S.No Source of TFA Category of Foods Food Items with their

TFA content (g/100 gm)

I

TFA formed during partial

hydrogenation of vegetable

oils e.g. vanaspati,

margarines

(i) Baked foods Cakes*(2.7), Cookies*(5.9),

Muffin*(1.3), Brownie*(3.4),

Pizza*(0.5)

(ii) Foods fried/cooked

in partially

hydrogenated

vegetable oil

French fries*(4.2-5.8)

II

TFA found naturally in

milk, milk products and

body fat of ruminant

animals (e.g. cattle,

buffalo, goats, etc)

Naturally occurring

foods

Milk**, dairy products**,

Meat from ruminant

animals** (mutton, beef etc.)

* Mozaffarain et al, 2006. **Exact TFA content among these food items is not known; and requires further investigation

Table 2.9: Fatty Acid Content of Some of the Cooked Food Items Frequently

Consumed in India (g/typical serving)

(Misra et al, 2009a)

# Fatty acids have been calculated on thebasis of fatty acid content of raw ingredients present in

food articles (Ghafoorunissa and Krishnaswamy, 1994; Gopalan et al, 1989) however TFA

content as per the laboratory analysis may differ.† Values for trans fatty acid content are given for

a typical serving. ‡Prepared in a combination of Vanaspati (hydrogenated fat) as shortening and

refined vegetable oil as the frying medium. §Prepared in Vanaspati. * Prepared in refined

sunflower seeds oil.

Nutrients† Parantha‡ Bhatura‡ Pulao§ Pakora* Dosa* Samosa‡ Fried

potato

chaat§

Halwa§

Typical

serving

size (g)

80 60 275 100 90 70 100 100

Total fat

(g)

12.03 20.32 11.61 17.40 11.36 15.64 15.6 20.73

SFA (g) 2.01 2.52 2.76 1.65 1.23 2.28 3.75 4.91

MUFA (g) 2.42 4.58 2.22 4.21 2.77 3.60 3.00 3.90

PUFA (g) 4.38 11.04 0.76 11.11 7.12 7.12 0.65 0.81

n-3 PUFA

(g)

0.15 12.16 0.06 0.09 0.22 0.09 0.12 0.33

n-6 PUFA

(g)

4.23 10.90 0.70 11.07 6.90 7.03 0.53 0.73

TFA (g) 2.72 4.45 5.30 0.21 0.142 2.79 7.95 10.6

39

2. 3 METABOLISM OF TRANS FATTY ACIDS

Although there is a clear understanding about the digestion, absorption and

metabolism of fats and fatty acids (as given in box and figure 2.5), there is scanty

literature available on the exact metabolism of trans fatty acid. The exact

biochemical methods by which trans fatty acids produce specific health problems

are a topic of continuing research. One theory is that the human lipase enzyme

works only on the cis configuration and cannot metabolize a trans fatty acids. A

lipase is a water-soluble enzyme that helps digest, transport, and process dietary

lipids such as triglycerides, fats, and oils in most of the living organisms. The

human lipase enzyme is ineffective against the trans configuration, so trans fatty

acid remains in the blood stream for a much longer period of time and is more

prone to arterial deposition and subsequent plaque formation.While the

mechanisms through which trans fatty acids contribute to coronary heart disease

are fairly well understood, the mechanism for trans fatty acids effect in diabetes is

still under investigation (Aro et al, 1997).

Figure 2.6: Digestion and Absorption of Fats in Human Body

(Source; Mahan and Escott-Stump, 2008)

40

Digestion, Absorption and Metabolism of Fats: Lipid metabolism is closely connected to the

metabolism of carbohydrates which may be converted to fats. Fatty acids are usually ingested as

triglycerides (triacylglycerols), but being water insoluble they cannot be absorbed by the intestine.

Therefore, they are first emulsified in the small intestine by bile salts forming micelles. Micelles

also serve as transport vehicles for those lipids that are less water-soluble than fatty acids, such as

cholesterol or fat-soluble vitamins A, D, E, and K.

Digestion of Fats: The emulsification of fats renders them susceptible to hydrolysis by pancreatic

lipase; which is virtually specific for the hydrolysis of primary ester linkages, the 1 or the 3 ester

bonds. As a result of this conversion 2-monoglyceride (2-monoacylglycerols) is formed.

Absorption of Fats: Short-chain fatty acids (up to 12 carbons) are absorbed directly through the

villi of the intestinal mucosa, enter the blood via capillaries that empty into the portal vein and are

transported via lipid carrier proteins directly to the liver, where they are used for energy

production. 2-Monoglycerides, long-chain fatty acids (more than 12 carbons), cholesterol and

lysophospholipids are absorbed from the lumen by intestinal mucosal cells, where they are

incorporated into lipoproteins and directed to the lymphatic system. Once across the intestinal

barrier, the triglycerides are re-synthesized. The triglycerides and other lipids (phospholipids and

cholesterol) appear in the form of chylomicrons that passes through the lymphatic vessels of the

abdominal region and later to the systemic blood. In the capillaries the extracellular enzyme

lipoprotein lipase (activated by apo C-II) hydrolyses triacylglycerols to fatty acids and glycerol

which are taken up by the cells in the targeted tissue. In muscle, the fatty acids are oxidized for

energy and in adipose tissue they are re-esterified for storage as triacylglycerols (stored as fat in

adipose tissue). The remnants of chylomicrons, depleted of most of their triacylglycerols but still

containing cholesterol and apolipoproteins, travel in the blood to the liver. In liver they are taken

up by endocytosis and processed into the various lipoprotein forms particularly VLDL-c and LDL-

c. Triacylglycerols that enter the liver by this route may either be oxidized to provide energy or act

as precursors for the synthesis of ketone bodies. In brief Chylomicrons carry diet-derived lipids to body cells, VLDL-c carry lipids synthesized by

the liver to body cells, LDL-c carry cholesterol around the body, HDL-c carry cholesterol from the

body back to the liver for breakdown and excretion (Figure 2.6).

Metabolism of Fats: The main pathways of lipid metabolism are lipolysis, beta-oxidation,

ketosis, and lipogenesis. Lipolysis is the breakdown of lipids, which involves the hydrolysis of triglycerides into free fatty

acids. β-oxidation is a cyclical process by which fatty acids, in the form of Acyl-CoA molecules, are

broken down in mitochondria and/or in peroxisomes to generate Acetyl-CoA, the entry molecule

for the Citric Acid cycle. In this process two carbons are removed from the fatty acid per cycle in

the form of acetyl CoA, which proceeds through the Krebs cycle to produce ATPs, CO2, and

water. Ketosis is a metabolic state that occurs when the liver converts fat into fatty acids and ketone

bodies, which can be used by the body for energy. It occurs during prolonged starvation and when

large amounts of fat are eaten in the absence of carbohydrate i.e. when the rate of formation of

ketones by the liver is greater than the ability of tissues to oxidize them. Lipogenesis is a process by which acetyl-CoA is converted to fats. It occurs in the cytosol. The

fatty acids are derived from the hydrolysis of fats, as well as from the synthesis of acetyl CoA

through the oxidation of fats, glucose and some amino acids. Lipogenesis from acetyl CoA also

occurs in steps of two carbon atoms. NADPH produced during the pentose-phosphate shunt is

required for this process. Phospholipids generated from triglycerides (TG) form the interior and exterior cell membranes

and are essential for cell regulatory signals (FAO/ WHO, 2003; Mahan and Escott-Stump, 2008).

41

2.3.1 Metabolism and Mechanism of Action of Trans fatty Acids

In general, nearly all isomeric cis and trans fatty acids (both ruminant and

industrial), when fed as part of a mixed diet, are efficiently absorbed and

incorporated into chylomicrons with the possible exceptions of fatty acids with

double bonds in the Δ2 to Δ7 positions.

Once the chylomicrons reach the liver, the fatty acids are repackaged into

triacylglycerols and exported into the circulation in the form of VLDL-c and

LDL-c (with little or no discrimination between cis and trans isomers in

triacylglycerol synthesis). Thereafter they are transported to the peripheral tissues,

where they are hydrolysed and taken up by the cells. In animal studies the

hydrolysis of cholesterol esters containing trans fatty acids was significantly lower

than those with cis double bonds highlighting that there is specificity in the

manner in which TFA are utilized by acyltransferases (Kinsella et al, 1981).

In human plasma, fatty acids in position 2 of phosphatidylcholine are transferred

to cholesterol to form cholesterol esters by the enzyme lecithin cholesterol acyl

transferase which strongly discriminates against the incorporation of trans isomers

of linolenic acid. In vivo, trans fatty acids are preferentially esterified into the Sn-l

position of phospholipids although trans-cis isomers of unsaturated fatty acids

may be acylated into Sn-2 position, particularly when saturated fatty acids occupy

position Sn-l. To quote an example di-trans 18:2 is incorporated preferentially into

position 1 of phosphatidylcholine and into the Sn-1 and Sn-3 positions of the

triacylglycerols, like the saturated fatty acids. In contrast, trans-cis fatty acids (9c,

12t-18:2) like linoleic acid (di-cis fatty acid) is incorporated into the Sn-2

position. It therefore, appears that the trans-15 ethylenic bond may be perceived as

a single bond by the acyltransferases involved. Support for this hypothesis comes

from a finding that esterification of 9c,12t-18:2 into position 2 of

phosphatidylcholine was similar to that of 9c-18:1.Once the plasma lipids reach

other tissues, both cis and trans fatty acids are rapidly taken up and incorporated

into tissue lipids. However, trans PUFA (9c, 12c, 15t-18:3) is selectively

incorporated into cardiolipin (phospholipid occurring primarily in mitochondrial

42

inner membranes) in a very similar manner to linoleic acid which is its structural

analogue.

The amounts of trans fatty acids absorbed and incorporated into tissue lipids

depends on their concentration in the diet. The deposition of trans fatty acids in

tissues may be selective. Thus adipose tissue and liver generally contain higher

levels of TFA than other tissues (Table 2.10) while, minimum deposition of trans

18:1 occurs in the brain (Schrock and Connor, 1975). After cessation of feeding,

depletion of trans 18:1 from the tissues occurs at a rate equivalent to that observed

for saturated fatty acids, normally taking about 4 to 8 week on the other hand

several studies have reported that trans fatty acids are oxidized at rates equivalent

to the corresponding cis isomers (Alfin-Slater and Aftergood, 1979; Kinsella et al,

1981). One study reported that animals consuming a diet containing trans

octadecenoate for a prolonged period might accumulate the trans fatty acids in

their depot fat, while in another study it was reported that trans 18:2 was rapidly

catabolized in rat liver, whereas cis 18:2 was elongated and acylated into

glycerolipids. Complete oxidation of trans isomers may not occur in all instances

and shortened isomers, i.e., trans 16: 1 and trans 14: 1 may accumulate (Wood,

1979).

Table 2.10: Trans Fatty Acid Concentration in Human Tissue Samples

Human Tissue Samples Trans Fatty Acid Concentrations (%)

Adipose Tissue * 2.4 to 12.2

Liver Tissue * 4.0 to 14.4

Heart Tissue * 4.9 to 9.3

Aortic Tissue * 2.3 to 8.8

Serum lipid (t18: 1) 1.9

Serum lipid (t18: 2) 0.8

Erythrocytes (t18: 1) 2.4

Erythrocytes (t18: 2) 0.7

* Primarily trans 18:1, but also contains trans 18:2

(adapted from Perkins et al, 1977)

43

Desaturation and Elongation: The incorporation of trans fatty acids into

membrane phospholipids may alter the packing of the phospholipid and

possibly influence the physical properties of the membrane as well as the

activities of the membrane associated enzymes (Kinsella et al, 1981), like

elongase, desaturase and PG synthetase. The trans fatty acids are converted

to CoA esters which act as substrates for acyl transferases and some

desaturases. Certain trans fatty acids are elongated and desaturated, and

possibly may decrease the availability of the natural cis polyunsaturated

fatty acids for prostaglandin (PG) synthesis by displacing them from the

various phospholipid fractions. Certain positional isomers of trans 18:1 can

be desaturated by ∆9 desaturase, and thus may compete with stearic acid

(18:0) which is the normal substrate for this desaturase.

Trans Fatty Acid; Linoleic Acid and Alpha Linolenic Acid: Animal

studies have suggested that di-trans-18:2 inhibits the elongation and

desaturation of linoleic and alpha linolenic acids. Linoleic acid is the

critical essential fatty acid which serves as the dietary precursor of

arachidonic acid (AA; 20:4n-6), while ALA is converted to

eicosapentanoic acid (EPA) which is further converted to docosahexaenoic

acid (DHA) in the body. Arachidonic acid (AA; 20:4n-6) and DHA

(22:6n-3) are critically important in fetal and infant growth as well as the

development of central nervous system (Elias and Innis, 2001).

Arachidonic acid is found in cell membrane phospholipids and cell

signaling pathways in cell division; and is the principal precursor of the

prostaglandin (PG), thromboxane, prostacyclin, and related endoperoxides

(Fig 2.6 and 2.7). There is clinical evidence supporting a relation between

blood lipid AA and infant growth and experimental evidence showing that

dietary AA reverses the growth failure resulting from deficiency of

essential fatty acids (Shoji et al, 2011). DHA on the other hand is involved

in visual and neural functions as well as neurotransmitter metabolism, its

concentrations being high in retinal and brain membrane phospholipids.

44

Liver microsomes have three desaturases which act on carbons 5, 6, and 9

of dietary fatty acids (Elias and Innis, 2001). The ∆6 desaturase which acts

on dietary linoleic acid (18:2 n-6) is a rate controlling enzyme in PUFA

synthesis. The ∆6 and ∆5 desaturases are involved in the conversion of

essential fatty acids to PG precursors [eicosatrienoic acid (20:3n-6)] and

arachidonic acid (20:4n-6); and since trans isomers of mono and dienoic

acids may inhibit these desaturases, they affect PG metabolism and their

diverse functions. It has been suggested that the trans isomers of oleic acid

(18:1) and linoleic acid (LA; 18:2 n-6), have adverse effects on growth and

development by inhibiting the desaturation and elongation of linoleic (LA)

and α-linolenic acid (ALA; 18:3n-3) to AA and DHA, respectively. In a

study, when trans-18:3 isomers were fed to animals in the form of heat-

isomerized linseed oil, they brought about a decrease in the concentration

of arachidonic acid (20:4 n-6) as well as in the ratio of arachidonic acid

(20:4 n-6) to linoleic acid (18:2 n-6) in the phospholipids of liver in

comparison to the animals fed fresh linseed oil. However, there are

conflicting views on this as some studies suggest that this only occurred

when very high levels of trans 18:3 isomers were fed.

Trans Fatty Acid and Essential Fatty Acid: Animal studies suggest that

trans fatty acids in the diet tend to increase the need for essential fatty acid

(EFA). In EFA deficiency, trans fatty acids accentuate dermal symptoms

and suppress growth and even relatively low levels of dietary trans

C18:2n-6 reduced the liver desaturase activity. Dietary trans 18: 1 inhibits

the conversion of linoleic acid (l8:2n-6) to arachidonic acid (20:4n-6) and

that of oleic acid (18:1) to mead acid (20:3n-9) apparently by acting as a

competitive inhibitor for the desaturase enzyme. This may partly explain

the mechanism by which trans monoenes (and trans, trans dienes)

exacerbate EFA deficiency symptoms (Figure 2.6).

Trans Fatty Acid and Lipoproteins: In controlled trials, consumption of

trans fatty acids reduces the activity of serum paraoxonase, (deRoos et al,

45

2002) an enzyme that is closely associated with HDL cholesterol, and

impaired postprandial activity of tissue plasminogen activator. (Muller et

al, 2001). In humans, TFA consumption increases plasma activity of

cholesteryl ester transfer (CET) protein, the main enzyme for the transfer

of cholesterol esters from HDL to LDL and VLDL cholesterol. This

increased activity may explain decreases in the levels of HDL and on the

other hand increases in the of LDL and VLDL cholesterol levels observed

with intake of trans fatty acids. Trans fatty acids also influence fatty acid

metabolism of adipocytes, resulting in reduced triglyceride uptake,

reduced esterification of newly synthesized cholesterol, and increased

production of free fatty acids. Consumption of TFA rich diets increases the

fasting plasma CET protein activity relative to the other major dietary fatty

acids. Although many other factors, such as lipoprotein receptor activity

and rates of lipoprotein secretion, could be involved, studies showing

increased fasting ratios of LDL to HDL cholesterol after short-term

consumption of high TFA diets support the role for TFA in regulating CET

protein activity (Mozaffarian et al, 2006).

In respect of Apo-lipoprotein, trans fatty acids appear to affect lipid

metabolism through several pathways. In vitro, trans fatty acids alter the

secretion, lipid composition, and size of apolipoprotein B-100 (apoB-100)

particles produced by hepatic cells (Mitmesser and Carr, 2005). Diets rich

in TFAs have also been shown to increase plasma concentration of

apolipoprotein a [apo(a)] compared with diets containing similar amounts

of oleic acid, stearic acid, palmitic acid or SFA combinations (Mozaffarian

et al, 2006).

Effects of Trans Fatty Acid on Eicosanoid Production: The eicosanoids

are derived primarily from arachidonic acid by the action of cyclo-

oxygenases and lipoxygenases (Figure 2.7 and 2.8); and they have a wide

range of functions in tissues at low levels, especially in relation to

inflammation. Fatty acids in the diet with trans double bonds could

46

potentially inhibit eicosanoid metabolism by reducing the availability of

substrates or by inhibiting the action of specific enzymes. Certain studies

have shown that Trans-dienoic isomers in hydrogenated fat inhibited

prostacyclin released by endothelial cells in the presence of high level of

linoleic acid e.g. 14-trans-20:4 inhibited the conversion of arachidonic acid

(20:4; n-6) to thromboxanes, and was itself converted into other eicosanoid

metabolites, while 17-trans-20:5 and 19-trans-22:6 inhibited the 12-

lipoxygenase and cyclooxygenase pathways, respectively (Muller et al,

1998; Mozaffarian et al, 2006).

Trans Fatty Acid and Prostaglandin Biosynthesis: Linoleic acid is the

critical EFA that serves as the precursor of prostaglandin (PG),

thromboxanes, prostacyclin, leukotrienes, hydroxy fatty acids, and related

endoperoxides (Mozaffarian et al, 2006). Availability of precursor acids is

one of the important factors regulating the biosynthesis of PGs (Oh et al,

2005). In a study using very high concentrations of dietary trans, trans

linoleate (alone) and in combination with cis, cis 18:2 fatty acids, it was

observed that TFA affected the level of PG precursors in various tissues

and the capacity of blood platelets to synthesize PGs. Animal studies have

also indicated that TFA interfered with the metabolism of essential fatty

acids thereby impairing their conversion to PGs. Abnormally high levels

of dietary trans fatty acids exert a greater impact on PG production than is

apparent from their effects on levels of the respective PG precursor fatty

acids. This may indicate that the trans, trans 18:2 fatty acid or its metabolic

derivatives inhibited some of the enzymes involved in prostaglandin

synthesis. The possible inhibition of PG synthase by trans fatty acids may

further implicate them in the exacerbation of EFA deficiency symptoms.

This may in part explain why the classical clinical symptoms of EFA

deficiency are more severe in the rats receiving high dietary levels of trans,

trans 18:2 (Mozaffarian et al, 2006).

47

Figure 2.7: Essential fatty acid production and metabolism to form

Eicosanoids

(Source: Abramczyk et al, 2011)

48

Figure 2.8: Arachidonic acid cascade, depicting biosynthesis of AA eicosanoid

products.

(Source;http://en.wikipedia.org/wiki/Eicosanoid)

There are several possible mechanisms whereby TFA may affect both lipid and

non-lipid risk factors for cardiovascular disease. The cellular mechanisms relating

trans fatty acids to inflammatory pathways and other, non-lipid pathways are not

well established. Monocytes and macrophages, endothelial cells, and adipocytes

may each play a role. Trans fatty acids modulate monocyte and macrophage

responses in humans, increasing the production by monocytes of TNF-α and

interleukin-6. Trans fatty acids have been shown to increase circulating

biomarkers of endothelial dysfunction and to impair nitric oxide dependent arterial

dilatation. Each of these pathways warrants additional investigation, particularly

the potential influence of trans fatty acids on nuclear receptors, membrane

receptors, and membrane fluidity. (Baer et al, 2004)

49

Dietary TFA have also been seen to adversely affect various hemostatic and

hematobiological properties of blood, enzyme activities and alter the properties of

membrane phospholipids (Clandinin et al, 1991). Mitochondria from rats fed trans

fatty acids are more susceptible to swelling and show lower rates of oxidative

phosphorylation (Mozaffarian et al, 2006). Takatori et al (1976) concluded that

the influence of trans fatty acids appeared to be out of proportion to their

concentration in the diet because even relatively small concentrations

accumulating in the tissues, significant metabolic effects were observed.

2.4 HEALTH HAZARDS ASSOCIATED WITH TFA CONSUMPTION

Since TFA have a similar but straighter chemical structure as compared to the

‘cis’ form of fatty acid, the body therefore, recognizes this chemical structure and

uses it for same purposes as ‘cis’ form, but TFA stacks together just like saturated

fats sabotaging the flexible, porous functionality needed by the body (Mozaffarian

et al, 2006; Ghafoorunissa, 2008; ASCN/ AIN-1996).Trans-fatty acids can compete

with natural fatty acids in enzymatic reactions involved in prostaglandin synthesis

and can thus affect platelet activity and other critical functions. Metabolic studies

have shown various adverse effects associated with high TFA consumption (Table

2.10), which include:

Obesity: Findings from long-term studies suggest that TFA consumption

promotes weight gain, particularly the accumulation of abdominal fat. A

long term study on monkeys showed that high intake of TFAs (8 en %)

significantly increased weight gain with increased intra-abdominal fat

deposition and is also associated with insulin resistance even in the

absence of caloric excess (Kavanagh et al, 2007). Further TFA intake was

associated with hyperphagia, increased fat accumulation in the liver and

visceral adipose tissue as well as impaired glucose tolerance, all of which

are important features of the metabolic syndrome (Thompson et al, 2011).

In the cohort study on 16000 men who provided two measurements of

abdominal circumference over 9 years, each 2 en% increase in TFA

consumption was associated with a 2.7cm increase in abdominal

50

circumference after adjusting for measurement error and other risk factors

(Koh-Banerjee et al, 2003). In another study carried out on more than

41000 women who provided two measurements of weight over 8 years,

increases in TFA consumption were robustly associated with increase in

body weight in both cross-sectional and longitudinal analyses, after

adjustment for other risk factors (Field et al, 2007). In both of these

studies, changes in consumption of other fats, including total fat, SFA,

MUFA and PUFA, were much less strongly associated with

adiposity/weight gain, consistent with prior findings that neither total

dietary fat nor most fat subtypes are major determinants of body fat or

weight gain (Willett and Leibel, 2002).

Cardiovascular Diseases: Consumption of TFAs adversely affects blood

lipids and lipoproteins beyond changes in low density lipoprotein

cholesterol (LDL-c) and high density lipoprotein cholesterol (HDL-c).

TFA consumption raise the very low density lipoprotein (VLDL-c) and

LDL-c levels and lower the HDL-c, causing heart diseases. It also leads to

reduced triglyceride uptake and production of free fatty acids

(Ghafoorunissa, 2008; Bhardwaj et al, 2011a). Compared with MUFA or

PUFA, TFAs also raise the fasting triglyceride levels (Mozaffarian and

Clarke, 2009).

TFA consumption increases the levels of Lp (a) [lipoprotein-a] and

reduces the LDL-c particle size which is a possible independent CHD risk

factor (Mauger et al, 2003; Mozaffarian 2006; Bhardwaj et al, 2011a).

Intake of partially hydrogenated vegetable oils contributes to the risk of

myocardial infarction (Ascherio et al, 1994).There are several other

mechanisms through which TFA may affect both, lipid and non-lipid, risk

factors for cardio vascular diseases. TFA consumption has been found to

be associated with significantly higher levels of soluble TNF-α receptors

(circulating biomarkers of TNF- α system activity) after adjustment for

other risk factors that might influence inflammation (including age,

51

smoking, physical activity, medication, alcohol consumption and other

dietary habits) (Mozaffarian et al, 2004a). It also increases the levels of

inflammatory markers Interleucin-6 (IL-6) and high-sensitivity C reactive

protein (hs-CRP), specifically among obese individuals (Lopez et al,

2005). Studies suggest that TFA consumption increases TNF- α activity,

among individuals with greater adiposity, IL-6 and hs-CRP (Figure 2.9).

Thus, both observational studies and controlled trials indicate that TFA

consumption is proinflammatory, leading to thickening of the arteries

(atherosclerosis), diabetes, and sudden death due to heart failure

(Mozaffarian et al, 2004; Mozaffarian, 2006). Ecologic studies have

suggested that the consumption of TFAs is positively associated with

ischemic heart disease (IHD) risk (Gatto et al, 2003; Karbowska and

Kochan, 2011).

Increased risk of IHD associated with TFA intake involves elevations in

both apolipoprotein (a) [apo (a)] concentrations and the ratio of LDL to

HDL cholesterol. High concentrations of apo (a), LDL cholesterol and low

concentrations of HDL cholesterol in fasting plasma are important

independent predictors of IHD risk (Wild et al, 1997). In randomized

crossover study, targeted to investigate whether postprandial lipoprotein

metabolism is affected by the consumption of trans fatty acids revealed

that consumption of meals high in trans fatty acids results in higher

Cholesteryl ester transfer (CET) protein and postprandial lipoprotein

concentrations enriched with apo (a) than does consumption of meals free

of trans fatty acids (Figure 2.8). TFA consumption is also associated with

higher levels of several circulating markers of endothelial dysfunction,

including soluble intercellular adhesion molecule-1, soluble vascular cell

adhesion molecule-1 and E-selectin (Lopez et al, 2005). Endothelial

dysfunction is a key step in the development of atherosclerosis

(Mozaffarian et al, 2004).

52

Insulin Resistance and Diabetes: Insulin resistance is an important risk

factor for type 2 diabetes. It precedes the development of type 2 diabetes

and as already indicated it is associated with multiple cardiovascular risk

factors (obesity, dyslipidemia, low HDL-c, hypertension, impaired glucose

tolerance further leading to metabolic syndrome). TFA have shown to

increase insulin resistance and seem to have a unique cardio-metabolic

imprint that is linked to insulin-resistance and metabolic-syndrome

pathways (Micha et al, 2009).

Recent studies have shown that insulin resistance is initiated in adipose

tissue which in turn affects insulin sensitivity of skeletal muscle and liver.

Several animal and human studies have investigated the impact of dietary

TFA on glucose-insulin homeostasis. Animal studies have demonstrated

that both SFA and TFA decrease insulin sensitivity as is evident by

increase in plasma insulin levels (marker of insulin resistance) and

decrease in peripheral insulin sensitivity leading to decreased adipose

tissue and skeletal glucose transport (Ibrahim et al, 2005; Natarajan et al,

2005). Even as compared to SFA, TFA decrease the insulin sensitivity to a

far greater extent. Saravanan et al (2005) have reported that increasing the

linoleic acid (n-6 PUFA) in the diet, did not prevent the adverse effects of

TFA on insulin sensitivity, suggesting that it is necessary to reduce the

absolute levels of TFA. In addition SFA and TFA differentially alter the

expression of genes associated with insulin sensitivity in adipose tissues.

Compared to animal studies, human studies provided variable results on

TFA intake and insulin resistance (Thompson et al, 2011). Short term

human studies showed that among lean and healthy subjects, TFA intake

did not have significant effect on insulin resistance. The observation from

prospective cohort studies of TFA intake and type 2 diabetes risks have

been mixed (Thompson et al, 2011). Two studies showed no relation

between TFA consumption and type 2 diabetes risk, whereas another large

study showed significant positive association between TFA intake and

diabetes risk. However, TFA intake resulted in higher levels of plasma

53

insulin levels among individuals who were more predisposed to insulin

resistance, such as those with pre-existing insulin resistance, greater

adiposity or lower physical activity levels (Mozaffarian et al, 2009).

Further studies are required to confirm the effects of TFA on insulin

resistance and diabetes.

Health effects of TFA from Vanaspati: In a case control study in two

major Indian cities, an inverse association between mustard oil

consumption and IHD risk was seen, whereas a somewhat elevated risk

was observed with vanaspati consumption (Rastogi et al, 2004). As a large

proportion of the Indian population is predisposed to insulin resistance;

and the prevalence of diabetes and coronary heart disease is high,

reduction in TFA intake both through hydrogenated oils and the foods

consumed coupled with other dietary and life style changes, need to be

actively advocated.

Figure 2.9: Potential Physiological Effects of Trans Fatty acids

(Source; Mozaffarian et al, 2006)

54

Hypertension: Dietary intake of various fats may have different effects on

blood pressure. Experimental studies found that feeding rats with saturated

fatty acids resulted in impaired endothelial function (Gerber et al, 1999)

and enhanced sympathetic nervous system activities (Young et al, 1994)

which increased the blood pressure. In contrast, consumption of long-chain

ω-3 PUFAs modulated plasma phospholipid composition and cell

membrane fluidity, increased the production of vasodilators, and reduced

cardiac adrenergic activity (Valensi, 2005) all of which lowered the blood

pressure. Similarly the study by West et al, (2005) also showed that

MUFA also modified membrane phospholipids composition and vascular

reactivity the net effects could either raise or lower blood pressure.

However, direct effects of TFA on blood pressure remain largely unclear.

Due to the lack of flexible structure of their parent unsaturated fatty acid,

TFA display biological features more similar to SFA. Furthermore, since

TFA compete with other unsaturated fatty acids for enzymatic

desaturation, the presence of TFA may increase the demand for essential

PUFA (Kinsella et al, 1981).Studies linking fatty acids intake with incident

hypertension have yielded inconsistent results. In the Nurses’ Health

Study, a cohort of 121,700 US women aged 34-59 years (Witteman et al,

1989) and the Health Professionals Follow-up Study, with a cohort of

51,529 US men aged 40-75 years (Ascherio et al, 1992), no association

was found between baseline intake of SFAs, MUFAs, PUFAs, or TFA

assessed from food frequency questionnaire and incident hypertension

during a follow-up of 4 years. However, in a large-scale prospective cohort

study aimed to examine the association between intake of subtype and

individual fatty acids and the risk of developing hypertension among

28,100 women (aged ≥39 years and free of cardiovascular disease and

cancer), it was found that after adjusting for demographic, lifestyle, and

other dietary factors, higher intake of SFA, MUFA and TFA was each

positively associated with the risk of hypertension among middle-aged and

older women. The associations for SFAs and MUFAs were largely

55

attenuated by adjustment for potential intermediate factors including BMI,

diabetes, and hypercholesterolemia, while the associations for TFA

remained significant even after these adjustments. Intake of PUFAs was in

general not associated with the risk of hypertension.

Cancer: There are few studies investigating the relationship between

TFAs and certain cancers (Smith et al, 2009). The role of TFA in the

causation of cancers remains unclear. The EURAMIC study which

investigated the association between TFA content in adipose tissues and

the incidence of breast, prostate and colon cancer, demonstrated a positive

association between TFA and the incidence of colon and breast cancer but

not prostate cancer. In a case control study, serum TFA levels were

positively associated with the incidence of breast cancer. In another study

high consumption of TFAs was positively associated with distal colorectal

cancer (Vinikoor et al, 2010). Overall the role of TFAs in the causation of

cancer remains inconclusive and further studies are needed to establish an

association.

Liver Dysfunction: Trans-fatty acids are uniquely handled by liver i.e.

they are metabolized differently by the liver than other fats. In a study by

Mahfouz (1981) on the effect of dietary trans fatty acids on the delta 5,

delta 6 and delta 9 desaturases of rat liver microsomes in vivo it was

shown that the dietary trans fatty acids are differentially incorporated into

the liver microsomal lipids and act as inhibitors for delta 9 and delta 6

desaturases. The delta 6 desaturase is considered as the key enzyme in the

conversion of the essential fatty acids to arachidonic acid and

prostaglandins both of which are important to the functioning of cells

(Mahfouz, 1981). This indicates that the presence of trans fatty acids in the

diet may induce some effects on the EFA metabolism through their action

on the desaturases.

Non Alcoholic Fatty Liver Disease (NAFLD) occurs when fat is

deposition (steatosis) in the liver is not due to excessive alcohol use. It is

56

related to insulin resistance and the metabolic syndrome (Adams and

Angulo, 2006). Non-alcoholic steatohepatitis (NASH) is the most extreme

form of NAFLD which is regarded as a major cause of idiopathic cirrhosis

of the liver (Clark and Diehl, 2003). TFA consumption has been associated

with NAFLD. In an animal study, the livers of TFA-treated animals

contained larger vesicular structures consistent with

macrovesicularsteatosis (Collison et al, 2009). In this model, 30 per cent of

the dietary fat was in the form of partially hydrogenated vegetable oil, and

when this was replaced by isocaloric amounts of lard, the extent of

steatosis was substantially reduced, indicating greater liver injury with the

consumption of industrially produced TFA (Tetri et al, 2008). The highest

level of hepatic TG occurred in the TFA diet group with a 1.43-fold

increase in hepatic lipid content compared with control. Trans-fat feeding

increased serum leptin, and total cholesterol levels, while robustly

elevating hepatic lipogenesis and lipid catabolism. It was also associated

with increasing markers of inflammation, lipid storage, DNA damage, and

cell cycle impairment (Collison et al, 2009).

Infertility: Consumption of TFAs has shown to increase the risk for

ovulatory infertility (Bhardwaj et al, 2011a). In a prospective cohort study

of 18,555 married, premenopausal women without a history of infertility it

was concluded that dietary TFAs increased the risk of ovulatory infertility

when they replace carbohydrates or unsaturated fats that are commonly

found in vegetable oils. Dietary consumption of TFAs instead of MUFAs

was significantly related to the risk of ovulatory infertility. The

replacement of 2 en% from MUFAs with 2 en% from TFAs was

associated with a more than double risk of ovulatory infertility. Similarly,

the consumption of 2 en% from TFAs rather than from n - 6 PUFAs was

associated with a significantly greater risk of ovulatory infertility

(Chavarro et al, 2007). Further the intake of TFAs has been associated

with greater insulin resistance, risk of type 2 diabetes and concentrations

57

of inflammatory markers, which may also adversely affect ovulatory

function.

Complications in Pregnancy: High intake of dietary TFA have also been

associated with complications during pregnancy. A retrospective case

control study showed that pregnant women with high erythrocyte trans

fatty acids were at a much higher risk of preeclampsia than pregnant

women with low levels of the same (Williams et al, 1998). Similarly

another case control study also showed that erythrocyte TFA levels,

particularly the 18:2 trans, were positively associated with the risk of

preeclampsia (Mahomed et al, 2007). Further, increased fetal loss has been

attributed to high intake of TFAs possibly by down regulating the nuclear

transcription factor (PPARγ), which plays a pivotal role in placental

function (Morrison et al, 2008).

Fetal Development: The PUFA status of the developing fetus depends on

that of its mother, as confirmed by the positive relation between maternal

PUFA consumption and neonatal PUFA status. Researchers from the

MaastrichtUniversity in the Netherlands showed that consumption of

TFAs appeared to be associated with lower maternal and neonatal PUFA

status. In addition, the presence of TFAs in cord tissue was associated with

proportionally lower amounts of essential PUFAs, a reduced birth weight,

and a smaller head circumference (Hornstra, 2000).

TFA compromises fetal development. There is a significant negative

relationship between birth weight and the C18:1(trans-9) concentration in

maternal plasma phospholipids during early stages of pregnancy (Hornstra

et al, 2006). TFAs are known to impair the metabolism of n-6 and n-3

PUFA to long chain PUFA, therefore these may possibly have adverse

effects on fetal growth and development (Innis, 2006). In pre-mature

infants, plasma TFA level was inversely associated with birth weight.

Another study showed an inverse relationship between long chain PUFA

and TFA in cord blood lipids of full term infants. Similarly high maternal

58

intake of TFAs was inversely related to gestational age and birth weight.

TFAs may have adverse effects on growth and development through their

interference with essential fatty acid metabolism; direct effects on

membrane structures or metabolism, or secondary effect by reducing the

intake of the cis essential fatty acids either in the mother or the child

(Innis, 2006). The PUFA status of the developing fetus depends on that of

its mother, as confirmed by the positive relation between maternal PUFA

consumption and neonatal PUFA status. In lactating women, the dietary

TFAs tend to displace the essential fatty acids (linoleic acid and alpha-

linolenic acid) in human milk, and eventually the TFAs end up in the

plasma phospholipids and triglycerides of their breast-fed infants (Innis

and King, 1999). Since TFAs have a negative impact on PUFA

metabolism, it is important to minimize the consumption of TFAs during

pregnancy and lactation to prevent the adverse effects of TFAs on fetal as

well as neonatal (infant) growth and development.

Animal studies have shown that maternal TFA consumption may have

long term adverse effects on glucose-insulin homeostasis in the off-spring

too. Several studies have shown that high intake of TFAs during

pregnancy and lactation predisposes the off-spring to insulin resistance in

adult life. Studies have also shown that the mothers' hydrogenated

vegetable fat intake during pregnancy and lactation led to hypothalamic

inflammation and impaired satiety-sensing, which promote deleterious

metabolic consequences such as obesity, even after the withdrawal of the

causal factor. In other words, the effect remains even after the

consumption of the standard chow by the offspring. (Pimentel et al, 2011).

In another animal study examining the effects of several individual

trans18:1 fatty acid isomers on fat synthesis, and expression of lipogenic

genes in mammary and liver tissue in lactating mice revealed that milk fat

percentage was decreased by trans-7-18:1 and PHVO by 27% and 23%

respectively, compared with control group (Kadegowda et al, 2010).

59

High intake of TFA during pregnancy and lactation increases adiposity in

breastfed infants and their mothers. These adverse effects of TFAs on

adiposity are of major concern since the recent increase in incidence of

obesity, especially childhood obesity in India, could be attributed to an

increase in the consumption of fast foods. These findings strengthen the

importance of restricting the intake of TFA during pregnancy and

lactation.

Asthma and Allergy: Low intake of certain polyunsaturated fatty acids,

particularly n-3 and n-6 fatty acids, has been associated with the

development of asthma and allergies in children, but little is known

whether the configuration (cis or trans) of these fatty acids also plays a

role. In an international study on asthma and allergies in childhood, the

incidence of asthma, allergic cold and asthmatic eczema in children

aged 13-14 years was investigated in ten European countries (155

centres around the world).

A positive association was found between the intake of trans fatty

acids and these diseases. Such an association was not observed for

the intake of monounsaturated and polyunsaturated fatty acids (Weiland

et al,1999). In another prospective study, the associations between dietary

intake of fatty acids, antioxidants and relevant food sources of these

nutrients on the clinical manifestation of asthma in adulthood were studied

and it was concluded that even in adulthood a high margarine intake

increases the risk of clinical onset of asthma. The effect was stronger in

men than in women (Nagel and Linseisen, 2005)

Mental Health and Cognition: Evidence from prospective epidemiologic

studies have shown that higher intakes of saturated fatty acids and TFAs

since midlife, and lower polyunsaturated to saturated fat ratio are

associated with a faster rate of cognitive decline and it also might be

60

associated with neurodegenerative diseases (Morris et al, 2003; Morris et

al, 2006; Devore et al, 2009).

- Alzheimer's Disease: A study examining the associations between intake

of specific types of fat and incident Alzheimer disease suggested that the

intake of both trans fatty acids and saturated fats promote the development

of Alzheimer disease (Morris et al, 2003). In an invitro study it was

revealed that trans fatty acids compared to cis fatty acids increase

amyloidogenic and decrease nonamyloidogenic processing of amyloid

precursor protein (APP), resulting in an increased production of amyloid

beta (Aβ) peptides, main components of senile plaques, which are a

characteristic neuropathological hallmark for Alzheimer's disease (AD).

The study also showed that oligomerization and aggregation of amyloid

beta (Aβ) are increased by trans fatty acids. The mechanism identified by

this in-vitro study suggests that the intake of trans fatty acids potentially

increases the risk of Alzheimer’s disease or causes an earlier onset of the

disease (Grimm et al, 2011).

- Depression: Studies have shown a detrimental relationship between

dietary intake of TFA and the risk for developing depression, whereas

weak inverse associations were found for MUFA, PUFA and olive oil. In a

Mediterranean cohort study, a direct and potentially harmful association

was observed between TFA intake and the risk of depression. The

magnitude of this association was robust and persisted after several

degrees of control for confounding and several sensitivity analyses. The

study also demonstrated an inverse dose-response relationship for total

PUFA and MUFA intake. Further , in another study it was found that

people over six years who ate more of trans fatty acid containing foods had

a 48 per cent higher risk of depression than those who did not consumed

trans fatty acids (Sánchez -Villegas et al, 2011).

Adverse Impact on Quality of Life: Quality of life is a broad concept

that relates to all aspects of human life. Quality of life questionnaires have

61

become an efficient way of gathering data about peoples’ functioning and

well being. Also, the health status measures have been shown to be a

powerful predictor for chronic diseases and mortality over the long term in

clinical practice (Guyatt et al, 2007; Wannamethee et al, 1991). Further,

the ageing population has fostered the general concern for leading health-

related better quality of life. A study conducted by Ruanco et al (2011)

showed a harmful association between the highest intake of TFA and

several domains of health survey (SF-36 domains). The association

remained significant for the mental domains (except for mental health),

and bodily pain after controlling for potential cofounders including the

adherence to the Mediterranean diet. A possible explanation this finding is

that TFA promote endothelial dysfunction and increase the production of

pro-inflammatory cytokines that may interfere with neurotransmitter

metabolism and inhibit Brain-derived neurotrophic factor (BDNF)

expression among other physiological effects (Ruanco et al, 2011). BDNF

is a peptide critical for axonal growth, neuronal survival as well as

synaptic plasticity and function. Therefore, it is likely that the consumption

of foods containing TFA could increase the vulnerability to some mental

or neurological disorders or act negatively on mental quality of life.

2.5 RECOMMENDATIONS FOR DIETARY TRANS FATTY ACIDS

Several organizations have given recommendations for dietary TFA including the

National Academy of Sciences (NAS), which advises the governments of United

States and Canada on nutritional science for use in public policy and product

labeling programmes. The Dietary Reference Intakes formulated by NAS in 2002

for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and

Amino Acids have included their findings and recommendations regarding trans

fatty acids (Food and Nutrition board, 2005).These recommendations are based on

two key facts; firstly, "trans fatty acids whether of animal or plant origin are not

essential and provide no known benefit to human health"; and secondly, while

both saturated fatty acid and TFA increase the LDL-c cholesterol, trans fatty acids

62

also lowers the HDL-c cholesterol; thus increasing the risk of coronary heart

disease. Because of these facts and concerns, the NAS has concluded that there is

no safe level of TFA consumption. There is no adequate level, recommended daily

amount or tolerable upper limit for TFA. This is because any incremental increase

in trans fatty acids intake heightens the risk of coronary heart disease. Despite this

concern, the NAS have not recommended the elimination of TFA from the diet.

This is because TFA though in trace amounts, is naturally present in many animal

foods, and therefore its removal from ordinary diets might introduce undesirable

side effects and nutritional imbalances if proper nutritional planning is not

followed.

The NAS has, therefore, "recommended that TFA consumption be as low as

possible while consuming a nutritionally adequate diet" (Food and Nutrition

board, 2005). Similarly, the World Health Organization has tried to balance public

health goals with a practical level of TFA consumption, recommending in 2003

that TFA be limited to less than 1% of overall energy intake (PAHO/WHO Task

Force, 2006).

The US National Dairy Council has asserted that the TFA present in animal foods

are of a different type than those in partially hydrogenated oils, and do not appear

to exhibit the same negative effects (National Dairy Council, 2004). While a

recent scientific review agrees with the conclusion stating that "the sum of the

current evidence suggests that the public health implications of consuming trans

fatty acids from ruminant products are relatively limited", it cautions that this may

perhaps be due to the low consumption of trans fatty acids from animal sources

compared to the industrially produced (Mozaffarian et al, 2006).

63

Figure 2.10: Summary of the potential role of dietary Trans fatty acids on

human health and quality of life.

Compromis

ed Fetal

Developme

nt

Cognitive

Decline

Visceral

adiposity

Dyslipidemia

Systemic

Inflammation

Insulin

Resistance

Hypertension

The Metabolic

Syndrome

Type 2

Diabetes

Cardiovascular

Disease

Cancer

Infertility

Problems in

Pregnancy

Decreased

Quality of Life

Dietary

Trans

Fatty Acids

Asthma &

Allergies

Liver

Dysfunction

64

Due to paucity of data on dietary intake of TFA or their levels in food items India

had not formulated recommendations on TFA till 2009. Thereafter “Consensus

Dietary Guidelines for Healthy Living and Prevention of Obesity, the Metabolic

Syndrome, Diabetes, and Related Disorders in Asian Indians” was developed

wherein based on the WHO recommendation a level of <1% of total energy was

proposed for the Indians too (Misra et al, 2011). The same was recommended by

Indian Council of Medical Research (ICMR) and National Institute of Nutrition

(NIN) (ICMR, 2010). However, in the revised dietary guidelines for Indians-final

draft by the NIN/ ICMR (2011)there is an upward revision has been suggested

proposing that the energy contribution from TFA should be less than 2 en%

(Table 2.11).

2.5.1 Data on consumption patterns of Trans Fatty Acids

In developed countries such as Europe and North America, the average intake of

TFA varies between 2-4 en percent or between 5 -10 grams/ person/ day in a

commonly consumed daily diet providing 2000 kcal/day (Craig-Schmidt, 2006).

Data from developed countries report wide variation in the intake of TFAs ranging

from 0.5 en% (Greece, Italy) to 2.1 en% (Iceland) among men and from 0.8 en%

(Greece) to 1.9 en% (Iceland) among women, this works to nearly 1.2 to 6.7g/ d

among men and 1.7 to 4.1 g/d among women. Intake of TFA was lowest in

Mediterranean countries (0.5-0.8 en %). It was below 1 en% in Finland and

Germany (Table 2.12). Moderate intakes were seen in Belgium, The Netherlands,

Norway and UK and highest intake was observed in Iceland (Hulshof et al, 1999).

In European countries the intake of TFAs (mean ± s.d.) was reported as 2.40 ±

1.53 g/day for men and 1.98 ± 1.49 g/day for women (Van de Vijver et al, 2000)

whereas in Iran it was approximately 12.3 g/day (Table 2.12). Intake of TFA on a

typical American diet has been estimated to be between 8-15 g/day, although wide

variation exists between individuals (Khosla and Hayes, 1996; Mozaffarian et al,

2007).

65

Table 2.11: National/ International Recommendations for Dietary Trans

Fatty Acids

Organization Year Country Recommendation

for Dietary

Trans Fatty

Acids*

NAS 2002 Advisory for

Canada and

United States of

America

No adequate level

FAO/ WHO 2003 Global TFA <1 en%

Food and Drug

Administration 2006

2006 United States of

America

TFA intake be

reduced to <1% of

energy intake.

Health Council of The

Netherlands (Hunter et al,

2006)

2005 The

Netherlands

TFA intake as low

as possible. UL

1% energy

Consensus Dietary

Guidelines for Healthy

Living and Prevention of

Obesity, the Metabolic

Syndrome,

Diabetes, and Related

Disorders in Asian Indians

(Misra et al, 2011)

2010 India TFA <1 en%

ICMR/ NIN Nutrient

requirements and

recommended dietary

allowances for Indians

(ICMR, 2010)

2010 India TFA <1 en%

NIN revised recommended

dietary allowances

guidelines final draft (NIN/

ICMR, 2011)

2011 India TFA < 2 en%

*Total TFAs: from ruminants and partially hydrogenated vegetable oils

In India, however, data on dietary consumption of TFA are rather scanty (Misra

et al, 2009a). The main source of TFA in India is vanaspati (partially

hydrogenated vegetable oil) used as a cheaper substitute for “ghee” (clarified

butter). It is widely used in the preparation of commercially fried, processed,

ready to eat/ street foods/ Indian snacks/ sweets/ savoury items/ frozen/ pre-frozen

foods, packaged foods and premixed foods. Vanaspati accounts for nearly 10% of

66

the total production of vegetable oils and approximately 55% of vanaspati

manufactured in India is consumed mainly in Haryana, Punjab, Uttar Pradesh and

Himachal Pradesh where it is majorly used as a cooking medium (Ghafoorunissa,

2008). Estimates of TFA intakes in India during the past 2 decades, based on the

per capita availability of vanaspati ranged between 1.0 and 1.3 kg/ year

(Srinivasan, 2005), while the estimates of TFA based on edible fats and oil

supplies that were available in India in the 1980s (approximately 0.8 million

tonnes), and the population size in the said period, indicated an average

availability of 3g/ person/ day of vanaspati (Achaya, 1987). In North India, where

vanaspati is used as a cooking medium, the consumption can be as high as nearly

20 g/ person/ day. In Delhi, nearly 37% of the fats and oils market is for vanaspati

(Singh and Mulukutla, 1996).

In the bakery industry, vanaspati, butter and specialty fats (margarines,

shortenings, gels) account for 60, 20 and 10%, respectively, of total fat usage. The

indirect consumption of vanaspati through foods purchased at these outlets is not,

reflected in the National Sample Survey (1999-2000). However, while the direct

monthly per capita consumption range between 0.01 kg and 0.45 kg (average,

rural 0.06 kg/ per person/ month, urban 0.04 kg/ per person/ month). This survey

further indicated that vanaspati consumption as cooking oil is confined mainly to

four states: Haryana, Punjab, Uttar Pradesh and Himachal Pradesh (National

Sample Survey, 2001; Srinivasan, 2005). The TFA content of vanaspati, varies

widely depending upon the proportion of palm oil or its fraction used during the

hydrogenation process.

The consumption of foods containing vanaspati has increased in recent years. This

high intake of TFAs may be part of several changes in dietary and other life style

patterns among urban middle, upper middle and high-income groups contributing

to the present day high prevalence of diet-related chronic diseases. In recent years,

the intake of TFAs has increased due to increased consumption of fast foods,

ready to eat foods and bakery products which are usually prepared using

67

vanaspati. The limited data obtained indicate that TFA content of biscuits ranged

between 30 to 40% of the total fatty acids (Ghafoorunissa, 2008).

Table 2.12: Data on Dietary intake of TFA across countries

S.No Author Sample Location TFA Intake

1 Van de Vijver

et al, 2000

327 (men),

299(women)

Eight of

the

European

countries

Mean (+/-s.d.) TFA intake was

2.40+/-1.53 g/day for men and

1.98+/-1.49 g/day for women

(0.87+/-0.48% and 0. 95+/-

0.55% of energy, respectively)

2 Allison et al,

1999 11,258 USA

Mean percentage of energy

ingested TFA = 2.6%, mean %

of total fat ingested as TFA =

7.4%.

3 Mozaffarian et

al, 2007

7158 urban &

rural households

(35,924

individuals)

Iran

TFA accounted for 33% of fatty

acids or 4.2% of all calories

consumed (12.3 g/day).

4 Hulshof et al,

1999

-

14 of the

Western

European

countries

TFA intake ranged from 0.5%

(Greece, Italy) to 2.1% (Iceland)

of energy intake among men and

from 0.8% (Greece) to 1.9%

among women (Iceland) (1.2-6.7

g/d and 1.7-4.1 g/d,

respectively). TFA intake was

lowest in Mediterranean

countries (0.5-0.8 en %). It was

below 1% of energy in Finland

and Germany. Moderate intakes

were seen in Belgium, The

Netherlands, Norway and UK

and highest intake in Iceland.

5 Elias et al,

2002

60 pregnant

females Canada

Mean fat intakes (in

g/person/day) for the second and

third trimesters, respectively,

were: 85.8 and 73.9, total fat,

31.5 and 26.4 and TFA 3.8 and

3.4. Fat represented 28% of

dietary energy in both trimesters.

The major sources of trans-fatty

acids were bakery foods (33% of

trans-fatty acid intake), fast

foods (12%), breads (10%),

snacks (10%), and

margarines/shortenings (8%).

68

6 Sartika, 2011a 388 workers Indonesia

The mean intake of TFA was

0.48% of the total dietary

calories. Fried foods contributed

most to the total TFA consumed

at 0.20% of the total calories.

TFA intake from ruminant

products, and margarine/

hydrogenated vegetable oil

products were 0.09% and 0.06%

of calories, respectively. Every

additional 1% of SFA intake is

associated with an increase in

TFAs amounting to 0.03% of

total calories (r2=0.320, p=

0.000).

7 Castro et al,

2009

2,298 male and

female subjects,

including 803

adolescents (12

to 19 years), 713

adults (20 to 59

years) and

782 elderly

people (60 years

or over)

Brazil

The mean trans fatty acid intake

was 5.0 g/day (SE = 0.1),

accounting for 2.4% (SE = 0.1)

of total energy and 6.8% (SE =

0.1) of total lipids.

8 Yamada et al,

2010

225 adults (30 to

69 years) Japan

Mean total fat and trans fatty

acid intake was 56.9 g/day

(27.7% total energy) and 1.7

g/day (0.8% total energy),

respectively, for women and

66.8 g/day (25.5% total energy)

and 1.7 g/day (0.7% total

energy) for men.

9 Misra et al,

2009a

13-18 years

(n 797)

India

Mean TFA intake was 1.1 en %

(Males: 0-10.7; Females; 0-

10.2g/d)

18-69 years

(n 227)

TFA intake was1.0 en% for

males and 0.8 en % for females.

2.5.2 Global Regulations on Dietary Trans Fatty Acids

Regulation is a simpler and efficient way of reducing TFA intake than labelling

impositions, because it does not require campaigns educating consumers for the

negative health implications of TFA. Moreover, regulation also allows controlling

all type of products, including those from bakeries and restaurants and not only

the pre-packaged ones (Bysted et al, 2009).

69

Governments across the world have now made it mandatory to label the TFA

content along with other nutritive values on the nutrition label of commercially

prepared and packaged food items (Stender et al, 2012). The permitted level

ranges from <1% of the total calories by WHO (Uauy et al, 2009) to 2% of fats

and oils destined for human consumption by Denmark (Stender et al, 2006) (Table

2.13).

At International level, the World Health Organization recommended that fats for

human consumption should contain less than 4% of the total fat as trans and urged

the food industry to reduce the presence of TFA in their products to these levels

(Priego-Capote et al, 2007). However in 2003, WHO recommended that

governments around the world phase out partially hydrogenated oils if trans-fat

labelling alone doesn't spur significant reductions. WHO also recommended that

the trans fatty acids consumption should be less than 1% of the total daily energy

intake (WHO, 2003).

The experts acknowledged the current recommendation of a mean population

intake of TFA of less than 1en% may need to be revised in light of the fact that it

does not fully take into account the distribution of intakes and thus the need to

protect substantial subgroups from having dangerously high intakes. This could

well lead to the need to remove partially hydrogenated fats and oils from the

human food supply (FAO, 2008). The Centre for Food Safety closely monitors

the latest international developments regarding regulation of trans fatty acids.

The World Health Assembly resolved in 2004 that elimination of TFA

should be a key point for action by governments (WHO, 2004). WHO/ FAO

has recently completed an extensive review of latest research on the links of

TFA to CVD and diabetes and recommended that all countries should take urgent

regulatory steps to limit trans fatty acids in their diet so that clear danger to heart

health in vulnerable groups is avoided (Hunter et al,2006). Consumption of

trans fatty acids result in considerable potential harm with no benefit

(Mozaffarian et al, 2006).

70

The Codex Alimentarius Commission in its response to the WHO’s Action plan

for implementation of the global strategy on diet, physical activity and health

stated that "if the provisions for labelling of, and claims for, trans-fatty acids

do not affect a marked reduction in the global availability of foods

containing trans-fatty acids produced by processing of oils and by partial

hydrogenation, consideration should be given to the setting of limits on the

content of industrially produced trans-fatty acids in foods”. Further, it prohibits

the use of hydrogenated fats in foods meant for infants and children (FAO/ WHO,

2007).

In India several commercial food items with high TFA content are being sold by

food industry as well as roadside vendors; which is a matter of serious concern.

There are four major regulatory policy instruments used in India for

enhancing food safety; mandatory product standards; mandatory process

standards; licensing and prohibitions as well as voluntary product and process

standards. The edible oil industry is regulated under different standards.

a. Prevention of Food Adulteration Act, 1954: It includes specific standard on

edible oils giving broad specification for different oils [cottonseed, coconut,

groundnut, linseed, mahua, rapeseed, sunflower oil etc. and now in olive

(revised)]. It includes standards for blended vegetable oil, which allows

different oils to be blended and sold. However, the specifications do not lay

down any guidelines on the fatty acid composition of different oils. In

addition, there are specifications for vanaspati (hydrogenated vegetable oil).

Under this standard, companies can mix any quantity of any ‘harmless’ vegetable

oil in their brand in varied proportions. In September 2008, the ministry issued

notification for labelling of food, under the PFA. This notification includes

for the first time labelling for nutrition and health claims (PFA, 2008). For

edible oils, if the company makes nutrition or health claims, then it is required to

provide information on its package about the amount or type of fatty acids,

71

highlighting cholesterol, SFA, MUFA, PUFA and TFA contents. The PFA Rules,

1955 amended from time to time require that:

(a) The foods in which hydrogenated vegetable fats or bakery shortening is

used shall declare on the label that “Hydrogenated vegetable fats or bakery

shortening used-contain trans fatty acids”.

(b) A health claim of ‘trans fat free’ may be made where the trans fat is less than

0.2g per serving of food.

(c) A claim ‘saturated fat free’ may be made only where the saturated fat does not

exceed 0.1g per 100g or 100ml of the food.

b. The Bureau of Indian Standards (BIS) lays down different

specifications for edible oils and vanaspati. Giving requirements for physical

and chemical tests for moisture and insoluble impurities (per cent by mass),

Colour, Refractive index at 40ºC, Iodine value, unsaponifiable matter (per

cent by mass), Flash Point (ºC), heavy metals, aflatoxins and pesticides, free fatty

acid value expressed as oleic acid (maximum 5.0 and 0.25 per cent by mass for

raw and refined grades of materials), but no standard are laid for fatty acid

composition or trans fatty acids.

c. The AGMARK is a voluntary standard for Vegetable Oils and vanaspati

governed by the directorate of marketing and inspection of the Ministry of

Agriculture (Government of India) as per the Agricultural produce Grading

and Marking Act (1937). Blended Edible Vegetable oil and fat spread are

compulsorily required to be certified under AGMARK. However, it does not have

any standards for fatty acids or trans fatty acids. As regards SFA the limit has

been expressed as 0.1 g/ 100 g or 100 ml. However, in case of TFA value per

serving is required.

72

Table 2.13: Global/ Country Level Guidelines for TFA Consumption as well

as Food Labeling

Country Agency/ Year Guidelines

Global

WHO/ FAO, 2003

Global phase out of partially

hydrogenated oils (Hunter et al,2006)

Codex alimentarius, 2007

Prohibits the use of hydrogenated fats in

foods meant for infants and children.

Setting of limits on the content of

industrially produced trans-fatty acids in

foods (FAO/ WHO 2007).

Canada

Health Canada, 2005 Products with less than 0.2 grams of TFA

per serving may be labeled as free of

trans fatty acids (DCC, 2008).

Task force co-chaired by

Health Canada & Heart &

Stroke Foundation of

Canada, 2006

A limit of 5% TFA (of total fat) in all

products sold to consumers in Canada

(2% for tub margarines & spreads)

(HCHSFC, 2006).

United

States of

America FDA, 2003

FDA has declared label value for TFA as

0.5 g or less per serving. Products

entering interstate commerce on or after

January 1, 2006 must be labeled with

trans fatty acids. Food manufacturers

can list amounts of TFA with less than

0.5 gram (1/2 g) per serving as 0 (zero)

on the Nutrition Facts panel (FDA, 2003).

Denmark 2003

The limit for TFA is 2% of fats and oils

destined for human consumption. This

restriction is on the ingredients rather

than the final products. This has made it

possible to eat "far less" than 1 g of

industrially produced trans fatty acids on

a daily basis (Stender et al, 2006).

India Beauro of Indian

Standards (BIS)

No standard for fatty acid composition

or TFA (CSE, 2009).

Prevention of Food

Adulteration Act (PFA)

To provide information on the

package about the amount or type of

fatty acids, including cholesterol,

SFA, MUFA, PUFA and TFA (PFA,

2008). A health claim of ‘tran fat free’

may be made where the trans fatty acid is

less than 0.2g per serving of food.

AGMARK

It does not have any standards for

fatty acids or trans fatty acid. (CSE,

2009)

73

2.6 APPROACHES FOR LIMITING TRANS FATTY ACIDS FROM FOOD

SUPPLY

In order to successfully remove trans fatty acids from the food supply, an effective

alternative has to be brought in to practice, which can fulfill the requirements of

food manufacturers and is not a cause of concern for the consumer’s health.

Removing partially hydrogenated vegetable oils (PHVO) from the food supply

requires replacement with fats and oils of similar physical and sensory properties.

Most fats and oils consumed on a regular basis are a combination of several fatty

acids. Saturated fatty acids are by far more stable than polyunsaturated and

monounsaturated fatty acids. This stability plays an important role in improving

the shelf life of packaged foods and in retarding the rancidity of the oils including

the oils used for frying.

The major fatty acids found in food are palmitic, stearic, oleic, linoleic, and α

linolenic acids. Their structure, physical properties, functionality traits, and health

effects are summarized in Table 2.14.

2.6.1 Fats and Oils for Human Consumption

Identification of a suitable alternative to trans fatty acid containing fats/ oils

requires thorough understanding of their end use. Fats and oils for human

consumption vary in their fatty acid profile (Figure 2.11) and are usually separated

into 3 categories: cooking oils, frying oils and solid fats. The quality issues of

edible oils include oxidative stability, nutrient composition, and functionality.

Cooking Oils are required for the purpose of day to day cooking (sautéing/

vegetable preparation). Bland flavor, light color, good stability,

manufacturing processing and packaging flexibility are important for

cooking oils. Good choices to meet these requirements are polyunsaturated

and monounsaturated oils. Low PUFA oils are preferred to minimize the

likelihood of rancidity and the need for refrigeration. Cooking oils are also

suitable for deep frying at household levels however repeated frying can

deteriorate the quality of the oil. These oils contain very little of TFA

74

(mainly occurring during refining and deodorizing) however, repeated

heating/ frying at household level can increase the TFA content. To curb

the formation of TFA during frying, consumer need to be made aware of

the ways to limit the TFA content.

Frying Oils are mainly used forcommercial frying applications which

includes restaurant/ commercial frying such as the preparation of deep-

fried foods and packaged foods like chips/ namkeen’s/ other snacks etc.

Oils for commercial frying require stability related to the thermal

deterioration processes of oxidation, hydrolysis, and polymerization. For

consumer acceptance, the fatty acid composition of the oils needs to have

20% to 30% linoleic acid to produce a desirable full deep-fried flavor to

the foods; however, higher levels of linoleic acid might introduce “off”-

flavours from oxidation. For restaurant use, oils need to be stable because

a long fry life is required and the oil has to withstand the high temperatures

of commercial frying. Food manufacturers prefer stable oils that can also

tolerate high temperatures and allow an extended shelf life for foods after

they are packaged.

Stable frying oils are characterized by increased amounts of oleic acid

(preferably in the moderate range of 50% to 65%), decreased amounts of

linoleic acid (desirable between 20% to 30%), and decreased amounts of

α-linolenic acid (preferably no more than 3%). It has been common to

acquire stable commercial frying oils by changing the fatty acid

composition through partial hydrogenation.

75

Table 2.14: Major fatty Acids Present in Foods

Fatty Acid Structure Physical

Property Functionality Trait Health Effect

Palmitic

Acid C16:0 Saturated

Solid at room

temperature

Stable in

storage and

during frying

Used for

preparation of

margarines,

shortenings, and

spreads As a cream

base for baked

products Desirable

smooth mouth feel

Increases LDL

cholesterol and

elevates the risk for

heart disease

Stearic Acid C18:0 Saturated

Solid at room

temperature

Stable in

storage and

during frying

Relative large

percent

converted to

oleic acid

Used to form

margarines,

shortenings, and

spreads As a cream

base for baked

products Promotes

more of a grainy

mouth feel

Little effect on serum

cholesterol levels

because a high

proportion is

desaturated to oleic

acid

Oleic Acid C18:1

Monounsaturat

ed with

1 cis double

bond

Liquid at

room

temperature

Relatively

stable in

storage and

during frying

High stability

generally a positive

feature. Oils

containing very

high amounts of

oleic acid tend to

produce undesirable

fried-food flavor,

sometimes

described as bland

or waxy, caused by

a lack of breakdown

products

Lowers cholesterol

and may slow

progression of

atherosclerosis

Linoleic

Acid

(omega-6)

C18:2

Polyunsaturate

d with

2 cis double

bonds

Liquid at

room

temperature

Unstable in

storage and

during frying

Small amount is

acceptable to food

flavors

Inverse association

between n-6

polyunsaturated fatty

acids intake and the

risk of coronary heart

disease

α Linolenic

Acid

(omega-3)

C18:3

Polyunsaturate

d with

3 cis double

bonds

Liquid at

room

temperature

Unstable in

storage and

during frying

Main source of off-

flavors because of

its tendency to

oxidize and

contribute to

rancidity in

packaged and fried

foods

Increased

consumption of n-3

fatty acids from fish

or fish oil

supplements, reduces

the rates of all-cause

mortality, cardiac

and sudden death,

and possibly stroke

76

Potential alternatives to partially hydrogenated oils for commercial frying

include naturally stable oils such as corn, cottonseed, palm, peanut, and

rice bran or modified fatty acid oils such as mid oleic corn, high oleic/ low

α-linolenic canola, high oleic sunflower, mid oleic sunflower, low α-

linolenic soybean, and mid oleic/ low linolenic soybean oils. In choosing

trans fatty acid free frying oils, due consideration needs to be given to the

cost, availability, oxidative stability, functionality in terms of the

appearance and texture, flavour, and nutrient composition of the options.

Specifically, some of these oils such as animal fats and tropical oils

contain high amounts of saturated fats.

Figure 2.11: Complete Fatty Acid Profile of Commonly Used Fats &

Oils in India All the values are in %. *Source; Nutrient requirement and recommended dietary

allowance for Indians (2010); National Institute of Nutrition, Indian Council of Medical

Research.

92

68

39

19 17 16 12 9.6 12 14 4 6

15 10

47

6

29

46

48 44

41.6

37

15

25.8 26

67 62

75

21

49

2 2

11

32.6 38 42

50

75

62 53

15 22

9

16

4 1

0.4 0.4 1 0.4 1 0.4 0.2

7 14 10

1

53

SFA MUFA LA ALA

77

Solid Fats: Solid fats are required to be used as shortening and provide

structure and texture in baking and frying.Functionality parameters in solid

fats (vanaspati, ghee, butter, bakers shortening/ margarine and spreads)

include the melting point, lubricity, moisture barrier, and creaming ability.

The parameters of fat content, emulsifiers, solid fat in blending, and

melting point need to be in place before the product development is

initiated. In the development of solid shortenings to reduce trans fatty

acids, functional parameters such as plasticity for extrusion into dough and

creaming properties are important. The dough should not be sticky or “oil

out” at high temperatures. Solid shortenings packed in cubes need to allow

handling without deformation.

Partially hydrogenated fats have been effective in achieving functionality

and stability requirements in solid fats. To meet the functionality and

stability requirements in solid fats while minimizing trans fatty acids,

many of the current options typically include significantly increasing

saturated fatty acids. Several consumer brands of solid TFA free

margarines have become available in recent years, as have solid

shortenings. The availability of these products for commercial use is

uncertain at this time.

2.6.2 Considerations for Selection of Trans Fatty Acid Alternatives

When evaluating alternatives to reduce trans fatty acids in the food supply, several

points need to be taken into consideration:

There are several different needs like cooking/ frying/ baking/ fat for

shortening etc., therefore different solutions for oils. As a result, there

cannot be a single solution in terms of alternative oils.

There are various applications with different attributes, including sensory

needs, the level of nutrition benefit sought, and functionality.

Food companies might have brand claims or product positions that drive

decisions regarding the oil choices.

78

Availability and cost considerations are paramount before a conversion

can happen. When evaluating alternatives to reduce trans fatty acids in the

food supply, several considerations need to be made. The trait-enhanced

oils also face the numerous challenges such as:

- Additional costs are incurred. A grower premium is provided to

farmers as an incentive for them to grow trait-enhanced beans/ seeds

and to compensate the growers for their efforts at the segregation of

trait-enhanced from the commodity oil seeds. There are also additional

oil processor costs related to the need to collect, crush, refine, and store

the oil separately.

- in the development of new varieties of oil seeds, long lead time is

required. The decision about which specific seeds to grow is made

several years in advance of the oil delivery; thus, contract planting is

necessary.

2.6.3 Alternatives to Partially Hydrogenated Fat

In recent years there have been a number of strategies suggested to reduce the

consumption of TFA at both population and individual in many of the developed

nations. In principle it is considered important that TFA are replaced preferably by

cis unsaturated fats from vegetable oils rather than saturated fats from tropical oils

or animal fats. The concern of the severe negative impact of TFA on human health

has led food industry to make a clear effort to search for alternatives. Some of the

potential ways to limit/ replace TFA include:

a) Modification of the partial hydrogenation process to produce fats with low

TFA levels

b) Use of plant breeding and genetic engineering to produce oil seeds with

modified fatty acid composition

c) Use of tropical oils, for instance, palm oil, palm kernel oil, coconut oil

d) Interesterification of mixed fats. Interesterification is the hydrolysis of the

ester bond between the fatty acid and glycerol (Tarrago-Trani et al, 2006; Lee

et al, 2008).

e) Genetic manipulation of soybean oil is providing alternative oils, which are

more stable.

79

The details of these approaches have been summarized in Table 2.15.

In view of the present scenario to replace dietary TFAs, two practical options are

available, 1) revert to a natural saturated fat without cholesterol which is most

likely palm oil or its fractions or 2) move to a newer model of modified fat

hardened by interesterification. Both of these options have been the subject of

nutritional scrutiny for approximately the last 40 years, and both have positive and

negative attributes.

2.6.4 Learning from the success of the developed nations

A number of successful approaches have been used globally to reduce the TFA

content of foods and hence the intakes of TFAs. Among the examples reviewed,

several common features can be highlighted, which appear to be central to

implementing successful approaches to reducing TFAs. First is science, or expert

national panels, which reviewed the situation regarding TFA consumption in their

respective jurisdiction and made concrete recommendations for their reduction,

which were appropriate to the local environment. Second, the role and importance

of the media in facilitating change cannot be overlooked. Active interest by the

media in increasing consumer awareness of, and pressurizing industry to meet the

challenges associated with reducing the TFA content of foods was a central aspect

of the TFA reduction activities in Denmark, Canada, New York and in Argentina.

This awareness stimulated and sustained consumer demand, industry action and,

in many cases, government involvement to ensure continued product

reformulation by the industry. Governments have approached the problem through

a variety of measures, reflective of local circumstances, but all programmes have

exhibited a degree of government involvement, which has ranged from the

introduction of regulatory limits, for example, Denmark or New York; to the

introduction of agricultural and tax measures to support the production of healthy

alternatives, for example, Argentina; to setting concrete objectives, coupled with

active monitoring, and publishing industry progress over a defined time interval to

sustain the voluntary commitments by industry to reformulate, for example,

Canada. Thus, the complexity involved in TFA reduction and replacement

80

throughout the food supply makes it absolutely necessary for all sectors

(government, industry, public health and academics) to work collaboratively to

reach TFA reduction/elimination goals. These actions also need to be supported

by both media and consumer awareness of the health concerns associated with

TFA intakes to be successfully implemented.

Table 2.15: Alternatives to Partially Hydrogenated Fat

(Eckel et al, 2007)

Type of

Alternative

Description Examples Advantages Drawbacks

Tropical oils

Oils that come

from tropical

plants

Palm oil

Palm kernel

oil

Coconut oil

Functionality

Economics

Availability

Past user experience

Negative health

effect associated

with high

saturated fat

content

Animal fats

Fats that come

from animals

Beef tallow,

Lard, Butter

Functionality

Past user experience

Negative health

effect associated

with high

saturated fat

content and

naturally

occurring

cholesterol

Trait-enhanced

oils

New oil seed

varieties that can

yield oils that are

stable without

requiring

hydrogenation

Low-linoleic

soybean and

canola oils,

Mid oleic

soybean and

sunflower

oils

High-oleic

soybean,

sunflower,

and

canola oils

Many new varieties

have been

developed

or are in research

and development

pipeline

Generally

acceptable

functionality for

frying

Generally higher

costs

Long lead time

for delivery

Uncertainties

regarding

availability

Blending liquid

soft oils with

harder

components

Blending partially

hydrogenated

vegetable oils,

fully hydrogenated

vegetable oils

(with PUFA and

MUFA converted

to stearic acid), or

tropical fats with

liquid vegetable

oils

Company

specific

products

Individually

formulated to

provide various

fatty acid

compositions and

melting points.

Used for frying or

baking depending

on the fluidity of

the fat

Modified

hydrogenation

process

Increasing the

pressure,

decreasing the

temperature,

and/or changing

Company

specific

products

Can selectively

reduce the amount

of trans fatty acids

produced during

hydrogenation

Extremely high

pressure and

concentrations of

catalysts

required can

81

the catalyst or

catalyst

concentration to

lower levels of

trans fatty acids

In some cases, trans

fatty acid

production has been

suppressed by up to

80%

reduce

commercial

viability

Fractionation of

tropical fats

Separating palm

oil into hard

fractions to be

used as structuring

fats for margarines

and shortenings.

Dry multiple

fractionation yields

at firststage hard

stearin and mostly

unsaturated olein,

and yields several

other fractions at

later stages

Company

specific

products

Fractions with

different solid fat

profiles and melting

point curves to

allow

versatility in

formulation

Negative health

effect associated

with highly

saturated hard

fractions

(including

palmitic [C16:0]

and palm kernel

oil containing

C12, C14, and

C16)

Interesterificati

on

A liquid and a hard

stock (e.g. palm

kernel oil, solid

palm fraction) are

blended together

and interesterified

Involves treating a

fat with an excess

of glycerol in the

presence of a

chemical or an

enzymatic catalyst

at arelatively low

temperature,

causing the

rearrangement or

redistribution of

the fatty acids on

the glycerol

portion of the

molecule, thus

producing fats

with different

melting profiles

and physical

characteristics than

the parent fat

Company

specific

products

Does not change the

degree of

unsaturation of the

fatty acids

Does not convert

cis into trans

isomers

If an enzymatic

catalyst is used,

resulting

interesterification

process is

continuous and

specific, with

steeper solid fat

curves to provide

better functionality

and few

unidentified

byproducts without

the need for

extensive post

processing

High cost of the

enzymatic

catalyst

Technology has

not been fully

examined for its

effects on health

Current evidence shows that TFA intake adversely affects the health. In view of

the adverse effects of trans fatty acids on health of population at large we need to

search out for suitable alternatives and develop TFA free fats/ oils. The fried foods

are quite popular among all and have been part of our conventional as well as

82

modern diets, thus these will continue to stay in the market along with baked

foods and therefore will be an integral part of Indian diet. The regulatory

authorities need to formulate strict guidelines to limit TFA content in the food

supply. The food industry and the manufacturers need to be educated regarding

ways to avoid the formation of TFA in fats/ oils during processing/ food

preparation. Active media participation in generating awareness regarding the

adverse effects of trans fatty acids and their sources can educate the consumer,

which can further generate the demand for healthier foods free of trans fatty acids

and pressurize the food industry to meet the demand.