Ingestion, Digestion, Absorption, Metabolism, Transport, Excretion Carbohydrates Lipids.

Ingestion, Digestion, Absorption, Metabolism, Transport, Excretion

Carbohydrates

Lipids

Ingestion, Digestion, Absorption, Metabolism, Transport, Excretion

Carbohydrates

Lipids

What happens when we eat?-entry to exitWhat happens when we eat?-entry to exit

• Ingestion (I)-food and drink in mouth

• Digestion (D)-breaking to food down to absorbable units

• Absorption (A)-absorbable units cross the gi tract to blood or lymph

• Transport (T)-movement about the body in blood or lymph to cells for metabolism

• Metabolism(M)-all the chemical reactions that occur in the body-more on this later in the course

• Excretion (E)-waste leaves body in urine and faeces primarily

• Whole idea with IDATME is to get nutrients to where (W) they are needed, when (W) they are needed, in the form (F) they are needed and in the quantity (Q) they are needed-IDATME and WWFQ must be a tightly choreographed operation or body shuts down

• Remember IDATME WWFQ

IDATME VIDEOIDATME VIDEO

• https://www.youtube.com/watch?v=08VyJOEcDos

https://www.youtube.com/watch?v=08VyJOEcDos

Carbohydrates

Chapter 2

Carbohydrates

Chapter 2

CarbohydratesCarbohydrates• More than just “sugar” and “starch”

• Provide the majority of calories in almost all human diets

• Carbohydrate classifications

– Carbohydrates

o Class of energy-yielding nutrients that contain only carbon, hydrogen, and oxygen, hence the common abbreviation of CHO

o CH2O is the basic formula and hence the name carbohydrate carbo = carbon and hydrate = H2O

o Simple carbohydrates contain only one or two saccharide units (monosaccharide and disaccharides). Mono = 1 and di = 2

o Complex carbohydrates contain many saccharide unit molecules (oligosaccharides (3-10 saccharide units and polysaccharides (> 10 saccharide units)).

Carbohydrates—(cont.)Carbohydrates—(cont.)

• Carbohydrate classifications—(cont.)

– Monosaccharides-single saccharide units

o Simplest of all sugars

o Most common

Glucose

Fructose

Galactose

Carbohydrates—(cont.)

Monosaccharides-building blocks of disaccharides, oligosaccharides and

polysaccharides

Carbohydrates—(cont.)

Monosaccharides-building blocks of disaccharides, oligosaccharides and

polysaccharides



– Monosaccharides—(cont.)

o Glucose

Also known as dextrose

Component of all disaccharides

Sugar into which the body converts all other digestible carbohydrates



– Monosaccharides—(cont.)

o Fructose or “fruit sugar” Sweetest of all natural sugars High-fructose corn syrup (HFCS)

o Galactose Does not occur in appreciable amounts

in foods Combines with glucose to form lactose



– Disaccharides

o Made of two linked monosaccharides

o Sucrose, maltose, and lactose are disaccharides. Sucrose or “table sugar”

Composed of glucose and fructose Occurs naturally in some fruits and

vegetables



– Disaccharides—(cont.)

o Maltose

Composed of two joined glucose molecules

Not found naturally in foods

Results from breakdown of starch in humans

o Lactose or “milk sugar”

Composed of glucose and galactose

Found naturally in milk

Least sweet of all sugars



– Disaccharides—(cont.)



• Complex carbohydrates

– Oligosaccharides

o 3-10 saccharide units

Found naturally in foods e.g. beans (e.g. raffinose and stachyose)

Some are tough to digest and are passed to the large intestine where bacteria make gas, short chain fatty acids and lactic acid from them

Are now considered to be dietary fibre



– Polysaccharides

o Complex carbohydrates

o Do not taste sweet

o Starch, glycogen, and fibre are types of polysaccharides.



– Polysaccharides—(cont.)

o Starch Glucose not used by plants stored as starch Grains

World’s major food crops Foundation of all diets Potatoes, dried peas and beans have

starch



– Polysaccharides—(cont.)

o Glycogen Animal (including human) version of

starch Liver glycogen releases glucose into

the bloodstream to maintain blood sugar between meals.

No dietary source of glycogen

Oligosaccharides-part of fibre

Carbohydrates—(cont.)Carbohydrates—(cont.)• Carbohydrate classifications—(cont.)

– Polysaccharides—(cont.)o Fibre

Generally considered a group name for oligosaccharides and polysaccharides that cannot be digested by human enzymes

Commonly referred to as “roughage” Categorized as water-insoluble or water-soluble Commonly assumed that fibre does not provide any calories However, fibre is broken down by bacteria in the colon to

form short chain fatty acids (acetic, proprionic and butyric) acids and lactic acid all of which can be used for energy

Gases (H2, CO2, CH4) is also formed by bacteria in the colon


• Sources of carbohydrates

– Grains, Vegetables, Fruits, and Dairy are provide the majority of carbohydrates.

– Nuts and dried peas and beans

– Grains

o Synonymous with “carbs”

o Classified as “whole” or “refined”

Carbohydrates—(cont.)Carbohydrates—(cont.)• Sources of carbohydrates—(cont.)

– Grains—(cont.)

o Whole grains

Consist of the entire kernel of a grain

Can be cracked, ground, or milled into flour

Composed of three parts

The bran

The endosperm

The germ (embryo)


– Grains—(cont.)

o “Refined” grains

Grains rich in starch but as the result of refining lose fibre, vitamins, trace minerals, fat, and phytochemicals found in whole grains so have to be enriched with e.g. folic acid

Enrichment

“Enriched” versus “fortified” -enriched foods have nutrients added back in after refinement . Fortified foods add more nutrients to the food, rather than replacing the removed nutrients.

Examples include white flour, white bread, white rice, and refined cornmeal.


• Sources of carbohydrates—(cont.)

– Vegetables

o Starch and some sugars provide the majority of calories in vegetables.

o “Starchy” vegetables provides three times more carbohydrate than the same amount of “watery” vegetables.


– Fruits

o Almost all of the calories in fruit come from sugar (mostly fructose), with small amounts of starch and minute quantities of protein providing negligible calories.

o Exceptions to this are avocado, olives, and coconut, which get the majority of their calories from fat.

o fibre is located in the skin of fruits.


– Dairy

o One cup of milk provides 12 g of carbohydrate in the form of lactose.

o Cottage cheese, which has about 6 g of carbohydrate per cup

– Empty calories

o e.g. soft drinks

o Carbohydrate content varies

Carbohydrates—(cont.)Carbohydrates—(cont.)• How the body handles carbohydrates

– Digestion

o Cooked starch begins to undergo digestion in the mouth by the action of salivary amylase.

o Most carbohydrate digestion occurs in the small intestine.

o Disaccharidase enzymes split disaccharides into monosaccharides.

o Monosaccharides are the only form of carbohydrates the body is able to absorb intact.

o Normally, 95% of starch is digested usually within 1 to 4 hours after eating.


• How the body handles carbohydrates—(cont.)

– Absorption

o Monosaccharides are absorbed through intestinal mucosa cells.

o Undigested starch passes with stools.

o Fibres may impair the absorption of some minerals—namely, calcium, zinc, and iron—by binding with them in the small intestine.

Carbohydrates—(cont.)Carbohydrates—(cont.)• How the body handles carbohydrates—(cont.)

– Metabolismo Fructose and galactose are converted to glucose

in the liver.o Liver releases glucose to maintain blood sugar

level.o Rise in blood sugar causes pancreas to release

insulin.o Postprandial state

Blood glucose concentration begins to drop. Pancreas releases glucagon. Glucagon stimulates liver to release glucose.


– glycaemic response to foods

o Increase in blood glucose levels

o glycaemic index (GI)

Determined by comparing the impact on blood glucose after 50 g of a food sample is eaten compared to the impact of 50 g of pure glucose or white bread= GI= 100

May help diabetics and athletes but is controversial and not found on food labels and not all foods have been assigned a GI value so its current utility is limited


– Glycaemic index



– Glycaemic response to foods

o Glycaemic index

Whole grain foods have a lower glycaemic index than white bread

potato > yam

legumes > root veggies

fruits ~ legumes

Fruits about equal to milks in GI (fructose ~ lactose in terms of GI)

Meats- GI = 0 (no carbs in meat)



• Low glycemic index (GI of 55 or less): Most fruits and vegetables, beans, minimally processed grains, pasta, low-fat dairy foods, and nuts.

• Moderate glycemic index (GI 56 to 69): White and sweet potatoes, corn, white rice, couscous, breakfast cereals such as Cream of Wheat and Mini Wheats.

• High glycemic index (GI of 70 or higher): White bread, rice cakes, most crackers, bagels, cakes, doughnuts, croissants, most packaged breakfast cereals.



– glycaemic response to foods—(cont.)

o glycaemic load= GI times the carbohydrate (grams) in food (note grams of carbohydrate means carbohydrate in food not including fibre)


– Glycaemic load

Not reliable for choosing healthy diet



o Glucose metabolism = balance between catabolism (tear down) and anabolism (build up)



-Functions of carbohydratesoGlucose for energy

Primary function of carbohydrates is to provide energy for cells.

Brain is totally dependent on glucose for energy.

Spares protein and prevents ketosis

oProtein sparing

Need to consume adequate carbohydrates


– Functions of carbohydrates—(cont.)

o Preventing ketosis

Without adequate glucose, fat oxidation prematurely stops at the intermediate step of ketone body formation.

Increased production of ketones causes nausea, fatigue, loss of appetite, and ketoacidosis.

Dehydration and sodium depletion may follow.


• Using glucose to make other compounds

– Glycogen

o Body’s backup supply of glucose

o One-third of the body’s glycogen reserve is in the liver.

– Nonessential amino acids

– Carbohydrate-containing compounds

– Fat

Carbohydrates—(cont.)Carbohydrates—(cont.)• Dietary reference intakes

– Total carbohydrateo The RDA for carbohydrates is set at 130 g for both

adults and children.o Acceptable macronutrient distribution range 45-65

% of calories– Fibre

o Adequate intake for total fibre is set at 14 g/ 1000 calories.

– Sugaro Maximal level of 25% of total calories or less from

added sugars is recommended.


However, World Health Organisation indicated on 5 March 2014 that keeping one’s simple sugar (mono and disaccharides) consumption to less than 5 % of daily calories (i.e. less than about 6 teaspoons of sugar) has added health benefits compared to keeping one’s simple sugar (mono and disaccharides) consumption than 10 % of calories (WHO’s previous recommendation).

This refers to all simple sugars whether they are added (pop, cakes) or naturally (e.g. honey, fruit) occurring.

Carbohydrates in Health PromotionCarbohydrates in Health Promotion

• Concentrate on fibre and whole grains

– Most consistent benefit of consuming adequate fibre is to relieve or prevent constipation.

– Linked to a decreased risk of heart disease, cancer, diabetes, and obesity

– Dietary guidelines recommend that adults and children consume at least one-half of their grain servings from whole grains.

o Results in 20% to 30% lower risk of atherosclerotic cardiovascular disease

Carbohydrates in Health Promotion—(cont.)


• Concentrate on fibre and whole grains—(cont.)– Dietary guidelines—(cont.)

o Less likely to develop insulin resistance and metabolic syndrome, common precursors of type 2 diabetes

o Associated with improved body weight management– Tips for choosing whole grains

o Factors contributing to the low intake of whole grains include consumers’ inability to identify whole grains, a lack of awareness of their health benefits, cost, taste, and unfamiliarity with how to prepare whole grains.



• How to increase dietary fibre

– Replace refined grains with whole grains.

– Choose a ready-to-eat cereal with 5 g of fibre or more per serving.

– Eat dried peas and beans two to three times per week.

– Eat at least five servings of fruits and vegetables daily.

– Eat a variety of plant foods daily.

– Increase fibre intake gradually to avoid GI intolerance.

– Consume adequate fluid.



• Limit added sugars

– Sugar adds flavor and interest.

– Limiting intake is prudent-added sugars contribute to obesity

– Sugar alternatives

o Sugar alcohols

o Nonnutritive sweeteners (e.g. sucralose

aspartame, saccharin, cyclamate)



• Limit added sugars—(cont.)– Sugar alternatives—(cont.)

o Sugar alcohols Sorbitol, mannitol, and xylitol Natural sweeteners derived from

monosaccharides Most are commercially synthesized. Incompletely absorbed Side effects Offer sweetness without promoting cavities



Limit added sugars—(cont.)

– Sugar alternatives—(cont.)

o Nonnutritive sweeteners Virtually calorie free Sweeter than sugar Do not raise blood glucose levels

o Risks and benefits of nonnutritive sweeteners Weight management Diabetes mellitus Safety



• Take steps to avoid dental caries

– Choose between-meal snacks that are healthy and teeth-friendly.

– Limit between-meal carbohydrate.

– Avoid high-sugar items.

– Brush promptly after eating.

– Chew gum sweetened with sugar alcohols.

– Use fluoridated toothpaste.



The most common sources of added sugars in the Canadian diet

– Soft drinks

– Cakes, cookies, and pies

– Fruit drinks and punches

– Dairy desserts such as ice cream

– Candy



• Sugar: too much of a good thing

– Behavioral problems in children-false

– Obesity-true

– Diabetes mellitus-type 2-true

– Atherosclerotic heart disease-true

Lipids-Chapter 4Lipids-Chapter 4

• Low-fat diets do not always mean weight loss.

• “Good” (unsaturated)

– Eat in moderation-too much causes weight gain

• “Bad” (saturated fat and trans fats)

– Limited-note however that now saturated fats are considered less problematic than before however recommendation is that dietary saturated fats make up less than 10 % of daily calories remains

LipidsLipids

• Four classes of lipids

– Fatty acids-mostly attached to triglycerides, phospholipids and cholesterol though a small pool of fatty acids are unattached and thus called free fatty acids

– Triglycerides (fats and oils)-most of the fat in our diets

– Phospholipids (e.g., lecithin)-least of the fat in our diets

– Sterols (e.g., cholesterol)-middling amount in our diets

Fatty acidsFatty acids

– Basically chains of carbon atoms with hydrogen atoms attached

– Vary in the length of their carbon chain and in the degree of unsaturation

– Carbon chain length

o Almost all fatty acids have an even number of carbon atoms in their chain.

o Long-chain fatty acids (11 or 13 carbons and above)

o Medium-(6-10 carbons)(some say 6-12 carbons) and short-chain (2-4 carbon) fatty acids

Fatty acids—(cont.)Fatty acids—(cont.)

– Degree of saturation

o When all the carbon atoms in a fatty acid have four single bonds each, the fatty acid is said to be “saturated” with hydrogen atoms.

o An “unsaturated” fatty acid does not have all the hydrogen atoms it can potentially hold; therefore, one or more double bonds form between carbon atoms in the chain.

Monounsaturated

Polyunsaturated


o All food fats contain a mixture of saturated, monounsaturated, and polyunsaturated fatty acids.


– Degree of saturation—(cont.)

o Saturated fats

Tend to be solid at room temperature

Animal lipids are richer in saturated fats compared to plant lipids.

The only vegetable fats that are saturated are palm oil, palm kernel oil, and coconut oil.

Fatty acids—(cont.)Fatty acids—(cont.)– Degree of saturation—(cont.)

o Saturated fats—(cont.)

Commonly known as a “bad” fat because it raises blood cholesterol levels

Raises total and LDL cholesterol levels

As levels rise, risk of coronary heart disease rises.

May also make the inner lining of arteries more prone to inflammation and the buildup of fatty plaques by interfering with the normal protective action of HDL cholesterol



o Unsaturated fats

Liquid at room temperature

Monounsaturated fats are the predominant fat in olives, olive oil, canola oil, peanut oil, avocado, cashews, almonds, and most other nuts.

Polyunsaturated fats are the predominant fat in corn, soybean, safflower, and cottonseeds oils and also in fish.



o Unsaturated fats—(cont.) Commonly known as “good fats” because when they

are eaten in place of saturated fats, they lower LDL cholesterol and raise HDL cholesterol



o Unsaturated fats—(cont.)

Linoleic acid

The essential n-6 fatty acid

Especially abundant in plant oils

Alpha-linolenic acid

The essential n-3 fatty acid

Found in flaxseed, canola, soybean, and walnut oils and in nuts, especially walnuts


– Degree of saturation—(cont.)o Unsaturated fats—(cont.)

Alpha-linolenic acid—(cont.) Can convert alpha-linolenic acid to

eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in the body (very inefficient conversion of 5 % or less) EPA and DHA are in fish oils

Stability of fats Degree of unsaturation influences the stability of

fats. Polyunsaturated fats are most susceptible to

rancidity. – Food manufacturers may add antioxidants or hydrogenate to

prolong shelf life. However, hydrogenation can produce trans fats.

Fatty acids—(cont.)Fatty acids—(cont.)• Fatty acids—(cont.)


o Unsaturated fats—(cont.) Hydrogenation and trans fats

Hydrogenation is a process that adds hydrogen atoms to heart healthy polyunsaturated oils to saturate some or all of the double bonds so that the resulting product is less susceptible to rancidity.

If all of the double bonds are saturated get a saturated fatty acid; if not all of the double bonds are saturated get trans configuration

Saturated fats increase the bad cholesterol and Trans fats increase the bad cholesterol and decrease the good cholesterol-this is bad news as hydrogenation process creates clogging of the arteries with fat.

Clogging of the arteries is atherosclerosis which increases the risk of heart attack and stroke.

Cis fats are generally heart healthy while trans fats are not heart healthy


• Examples of fatty acids in the next slides

• Designated by carbon number, number of double bonds (if any) and if double bonds are present then the position of the first double bond relative to the methyl end of the fatty acid

• So 18:0 has eighteen carbons and no double bonds

• So 18:1 (n-9) or 18:1 9 has eighteen carbons and one double bond with the double bond on carbon 9 and the methyl carbon being carbon 1

Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

65

REPLACE WITH FIG 5-2 ACETIC ACIDREPLACE WITH FIG 5-2 ACETIC ACID

Fig. 5-1, p. 140

Triglycerides Triglycerides

• Three (tri) fatty acids attached to a glycerol backbone (glyceride) and hence the name triglyceride

• Approximately 98% of the fat in foods

• Made of the same elements as carbohydrates

– Carbon, hydrogen, and oxygen

– Proportionately more carbon and hydrogen atoms to oxygen atoms in triglycerides compared to carbohydrates and thus triglycerides yield more calories per gram than carbohydrates

Triglycerides—(cont.)Triglycerides—(cont.)

• Functions of fat in the body

– Primary function of fat is to fuel the body.

– Other important functions in the body

o Insulate and cushion internal organs

o Help to regulate body temperature

o Facilitate the absorption of the fat-soluble vitamins A, D, E, and K when consumed at the same meal

Triglycerides—(cont.)Triglycerides—(cont.)

• Functions of fat in the body—(cont.)

– Essential fatty acids have specific functions in the body.

– Much interest in fish oils (omega 3 fatty acids (eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA))

o Results of some (not all!!) of the fish oil research inconclusive- fish oils lower blood plasma triglyceride concentrations and platelet reactivity for sure - may improve insulin sensitivity (efficiency with which insulin gets glucose into cells)

Other LipidsOther Lipids Phospholipids

– Phospholipids have a glycerol backbone with fatty acids attached like triglycerides.

o Difference is phosphate group replaces one of the fatty acids.

– Both fat soluble (because of the fatty acids) and water soluble (because of the phosphate group)

o Enables them to act as emulsifiers

– Structural components of cell membranes that facilitate the transport of fat-soluble substances across cell membranes

Other Lipids—(cont.)Other Lipids—(cont.)

• Phospholipids—(cont.)

– Precursors of prostaglandins

– Lecithin is the best-known phospholipid.

o Supplements unnecessary

o Not an essential nutrient


Cholesterol

– A sterol

o Waxy substance whose carbon, hydrogen, and oxygen molecules are arranged in a ring

– Occurs in the tissues of all animals

o Found in all cell membranes and in myelin

– Found exclusively in animals

o Liver and egg yolks are the richest sources.


• Cholesterol—(cont.)

– “Good” and “bad” cholesterol refer to the lipoprotein packages that move cholesterol through the blood.

– Not an essential nutrient

How the Body Handles FatHow the Body Handles Fat

• Digestion

– Minimal amount of chemical digestion of fat occurs in the mouth and stomach through the action of lingual lipase and gastric lipases, respectively.

– Duodenum

o Stimulates the release of the hormone cholecystokinin

Stimulates the gallbladder to release bile

Prepares fat for digestion

How the Body Handles Fat—(cont.)How the Body Handles Fat—(cont.)

• Digestion—(cont.)

– Most fat digestion occurs in the small intestine.

– End products of digestion are absorbed into intestinal cells.

– Small amount is excreted in feces.

– Digestion of phospholipids is similar.

– Cholesterol does not undergo digestion; it is absorbed as is.


• Absorption

– About 95% of consumed fat is absorbed.

- small fat molecules (short chain fatty acids, medium chain fatty acids, glycerol) go

direct to blood

- larger fat molecules (monoglycerides, long chain fatty acids) are packaged in

chylomicrons and released into lymph- from the lymph chylomicrons are passed into the blood to distribute dietary lipids throughout the body

How the Body Handles Fat—(cont.)How the Body Handles Fat—(cont.)• Fat metabolism (catabolism = tear down)

– Catabolism of fatty acids increases when

o Carbohydrate intake is inadequate (e.g., while on a very-low-calorie diet).

o Or catabolism of fatty acids is unavailable (e.g., in the case of uncontrolled diabetes).

– Fatty acids cannot be reassembled to make glucose.

– Inefficient choice of fuel for glucose-dependent brain cells, nerve cells, and red blood cells


• Fat anabolism (=build up)

– Most newly absorbed fatty acids recombine with glycerol to form triglycerides that end up stored in adipose tissue.

– Fat stored in adipose tissue represents the body’s largest and most efficient energy reserve.

– Adipose cells have a virtually limitless capacity to store fat.

– Fat reserves

o One pound of fat provides 3500 calories

Fat in FoodsFat in Foods

• Vital functions of fat

– Imparts its own flavor, from the mild taste of canola oil and corn oil to the distinctive tastes of peanut oil and olive oil

– Transfers heat to rapidly cook food, as in the case of frying

– Absorbs flavors and aromas of ingredients to improve overall taste

– Adds juiciness to meats

Fat in Foods—(cont.)Fat in Foods—(cont.)

• Vital functions of fat—(cont.)

– Creates a creamy and smooth “mouth feel” in items such as ice cream, desserts, and cream soups

– Adds texture or body to many foods, such as flakiness, tenderness, elasticity, and viscosity; for example, milk is watery and cheese is rubbery when fat is removed

– Imparts tenderness and moisture in baked goods, such as cookies, pies, and cakes, and delays staling

– Is insoluble in water, thus providing a unique flavor and texture to foods such as salad dressings


o Grains naturally contain very little fat.

o Unadulterated vegetables contain little or no fat.

o Fruits, with the exception of avocado, coconut, and olives, are naturally with minute quantities of fat.


• Dairy

– Classified into one of three subgroups: full fat, reduced fat, and fat free

o Fat in dairy products is predominately saturated, and full-fat products have more cholesterol than in the lower-fat options.

o Fat-free varieties of milk, yogurt, and cheese provide virtually no fat.

o The midrange is reserved for reduced-fat items—they have some of the fat and cholesterol removed yet retain some of the “mouth feel” characteristic of whole milk.

Fat in Foods—(cont.)Fat in Foods—(cont.)• Protein foods

o Fat added during cooking, such as frying or basting with fat, increases the overall fat content and counts as choices from the Oils group; it is recommended that meats be prepared by methods that do not add fat, such as baking, roasting, broiling, grilling, poaching, or boiling.

Fat in Foods—(cont.)Fat in Foods—(cont.)• Meats and fat content

– Untrimmed meats are higher in fat than lean-only portions.

– “Red meats”—namely, beef, pork, and lamb—are higher in saturated fat than the “white meats” of poultry and seafood.

– White poultry meat is lower in fat than dark meat; removing poultry skin removes significant fat.

– Fat content varies among different cuts of meat. The leanest cuts are beef loin and round, veal and lamb from the loin or leg, and pork tenderloin or center loin chop.


• Meats and fat content—(cont.)– Beef grades can be used as a guide to fat content

because grades are based largely on the amount of marbling.

– Shellfish are very low in fat but have considerable cholesterol.

– Most wild game is very lean; the fat content in bison, venison, elk, ostrich, pheasant (without skin), rabbit, and squirrel ranges from 2 to 5 g per 3-oz serving.

– Processed meats, such as sausage and hot dogs, may provide more fat calories than protein calories.


• Nuts and fat content

– Nuts have many healthy attributes; they contain plant protein, fibre, vitamin E, selenium, magnesium, zinc, phosphorus, and potassium in a low–saturated fat, cholesterol-free package.

o Nuts’ high fat content of 13 to 20 g/oz comes mostly from monounsaturated fats and polyunsaturated fats; walnuts are a rich source of alpha-linolenic acid.


• Cholesterol in foods

– Egg yolks have approximately 213 mg of cholesterol. The cholesterol content of typical cuts of beef, pork, lamb, and poultry is generally around 70 mg/3 oz. Veal averages slightly more at about 90 mg/3 oz. The exceptions are organ meats, which are very high in cholesterol. Egg whites, dried peas and beans, are nuts are cholesterol free.


• Oils

– Allowances are small.

Dietary Reference Intakes Dietary Reference Intakes

• The issue of how much of each particular type of fat is needed, how much is optimal, and how much is too much is complex and in some cases controversial.

• Total fat

– Neither an AI nor RDA is set for total fat due to insufficient data.

– An Acceptable Macronutrient Distribution Range (AMDR) is estimated to be 20% to 35% of total calories for adults.

Dietary Reference Intakes—(cont.)Dietary Reference Intakes—(cont.)

• Saturated and trans fat

– Additional macronutrient recommendation issued for both of these fats is that intake should be as low as possible within the context of a nutritionally adequate diet.

– Neither of these fats needs to be consumed in the diet.

Dietary Reference Intakes—(cont.)Dietary Reference Intakes—(cont.)• Essential fatty acids

– Both an Acceptable Macronutrient Distribution Range and Adequate Intakes have been set for the essential fatty acids linoleic acid and alpha-linolenic acid.

– AI should not be confused with Recommended Dietary Allowance.

– Essential fatty acid deficiency

o Body cannot make essential fatty acids.

o Symptoms of essential fatty acid deficiency include growth failure, reproductive failure, scaly dermatitis, and kidney and liver disorders.

Dietary Reference Intakes—(cont.)Dietary Reference Intakes—(cont.)

• Cholesterol

– Maximum of 300 mg/day of dietary cholesterol for healthy adults

– Dietary cholesterol has little impact on blood cholesterol levels

Fat in Health Promotion Fat in Health Promotion

• Message to eat less fat was too simplistic.

• Type of fat in the diet can affect serum lipids more than the total amount of fat.

• Eat less saturated fat and keep trans fat consumption as low as possible

– To cut saturated fat intake, experts recommend

o Limiting meat intake, especially red meat, and choosing lean varieties

o Reduced- or no-fat dairy products

o Hydrogenated fats should be avoided.

Fat in Health Promotion—(cont.)Fat in Health Promotion—(cont.)

• Limit total fat and go for unsaturated fats

– Most effective way to limit total and saturated fat and increase unsaturated fats may be with a plant-based diet.

• Limit cholesterol

– Cholesterol intake becomes less important when saturated fat intake is low.

• What about “fish oils?”

– American Heart Association suggests healthy people eat at least two servings of fish per week. Oily fish like salmon, anchovies, trout and mackerel are best choices

– Fish oil pills are an alternative source of omega-3 fats.

Ingestion, Digestion, Absorption, Metabolism, Transport, Excretion Carbohydrates Lipids.

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