FIBER IN FOODS

Presented by

Dr.T.Poongodi Vijayakumar

Head

Department of Food Science & Nutrition

Periyar University

Salem-11

Fiber is the fibrous

material present in plants

and their products like

fruits and vegetables.

Dietary fibre is defined

as that portion of food

derived from plant cells

which is resistant to hydrolysis /

digestion by the elementary

enzyme system in human being.

FIBRE IN FOODS

• Dietary fiber (fibre), sometimes called roughage, is the indigestible portion of plant foods having two main components — soluble (prebiotic, viscous) fiber that is readily fermented in the colon into gases and physiologically active byproducts, and insoluble fiber that is metabolically inert, absorbing water throughout the digestive system and easing defecation. It acts by changing the nature of the contents of the gastrointestinal tract, and by changing how other nutrients and chemicals are absorbed.

• Dietary fiber can be soluble (able to dissolve in water) or insoluble. Fiber cannot be digested by humans. However, soluble fiber absorbs water to become a gelatinous, viscous substance and is fermented by bacteria in the digestive tract. Insoluble fiber has bulking action and is not fermented, although a major dietary insoluble fiber source — lignans — may alter the fate and metabolism of soluble fibers.

• Chemically, dietary fiber consists of non-starch polysaccharidessuch as arabinoxylans, cellulose and many other plant components such as dextrins, inulin, lignin, waxes, chitins, pectins, beta-glucansand oligosaccharides. The term "fiber" is somewhat of a misnomer, since many types of so-called dietary fiber are not fibers at all.

TYPES OF DIETARY CARBOHYDRATES

Dietary Carbohydrates

Available Unavailable

Simple Sugars /

carbohydrates

Complex

Carbohydrates

Monosaccharide

Disaccharides

Starches

Dextrins

Dietary fiber

(intrinsic and

intact)

Functional

fiber (isolated

and

manufactured)

Water Soluble Water insoluble

Categories of Dietary Fiber

• Cellulose, found in bran, legumes, peas, root vegetables, cabbage family, outer covering of seeds, and apples

• Hemicellulose, found in bran and whole grains

• Polyfructoses (Inulin and Oligofructans)

• Galactooligosaccharides

• Gums, found oatmeal, barley, and legumes.

• Mucilages

• Pectins, found in apples, strawberries, and citrus fruits

• Lignin, found in root vegetables, wheat, fruits with edible seeds (such as strawberries)

• Resistant Starches, found in ripe bananas, potatoes

DIETARY FIBER

• Plant non-starch polysaccharides (cellulose, pectin, gums, hemicellulose, β-glucan, fiber in oat and wheat bran)

• Plant carbohydrates not recovered by alcohol precipitation (inulin, oligosaccharides and fructans)

• Lignin

• Some resistant starch (RS1 and RS2)

FUNCTIONAL FIBER

Isolated or extracted non digestible carbohydrates using chemical, enzymatic and aqueous steps of 3-4 degrees of polymerisation

• Plant (resistant starch, pectin and gums)

• Animal (chitin and chitosan)

• Commercially produced(resistant starch, polydextrose, inulin, indigestible dextrins)

DIGESTION OF FIBERFIBER

Anaerobic fermentation by colonic microflora

Short chain fatty acids (Acetate, Butyrate, Propionate)

Reduces pH of the gut

Favorable environment for

probiotic colonization

Fosters the growth of

Lactobacillus & Bifidobacterium

Butyrate –

preferred fuel

substrate for

colonocytes

where it

metabolised to

acetoacetate

and β-hydroxy

butyrate

Acetate and

Propionate enters

into liver and

metabolized into

source of energy;

propionate utilized

by the liver for

gluconeogenesis

and acetate

metabolized

peripherally

Products of fiber fermentation

• Volatile fatty acids – acetate – liver

– Propionate – liver

– Butyrate – colonocytes

• Gases– Methane – flatus and breath

– Hydrogen - flatus and breath

– Carbon dioxide - flatus and breath

• Energy for microbial growth - feces

• When soluble fiber is fermented, short-chain fatty acids (SCFA) are produced. SCFA are involved in numerous physiological processes promoting health, including:

• stabilize blood glucose levels by acting on pancreatic insulin release and liver control of glycogen breakdown

• stimulate gene expression of glucose transporters in the intestinal mucosa, regulating glucose absorption

• provide nourishment of colonocytes, particularly by the SCFA butyrate

• suppress cholesterol synthesis by the liver and reduce blood levels of LDL cholesteroland triglycerides responsible for atherosclerosis

• lower colonic pH (i.e., raises the acidity level in the colon) which protects the lining from formation of colonic polyps and increases absorption of dietary minerals

• stimulate production of T helper cells, antibodies, leukocytes, cytokines, and lymphmechanisms having crucial roles in immune protection

• improve barrier properties of the colonic mucosal layer, inhibiting inflammatory and adhesion irritants, contributing to immune functions

• SCFA that are not absorbed by the colonic mucosa pass through the colonic wall into the portal circulation (supplying the liver), and the liver transports them into the general circulatory system.

• Overall, SCFA affect major regulatory systems, such as blood glucose and lipid levels, the colonic environment, and intestinal immune functions.[51][52]

• The major SCFA in humans are butyrate, propionate, and acetate, where butyrate is the major energy source for colonocytes, propionate is destined for uptake by the liver, and acetate enters the peripheral circulation to be metabolized by peripheral tissues.

Beneficial effects of fiber

• low energy valve ( 1.5 – 2.5 kcal/g)

• increase in stool volume

• Promote laxation, blood cholesterol and blood glucose attenuation (SCFA – effective inhibitor of fatty acid and cholesterol synthesis and release glucose slowly) thereby reducing the risk of non communicable diseases

• Increases the colonic blood flow

• Lower luminal pH and modulation of the colonic flora by stimulation of beneficial bacteria and inhibition of undesirable bacteria

• Viscous fibers reduce the risk of duodenal ulcer by delaying the gastric emptying

Benefits continued….

• prevention of intestinal infection (butyrate down regulate the activity of transcription factor Nuclear Factor kappa – B (NF kB) – central regulator of immune and inflammatory responses)

• prevention of colorectal cancer (low pH depress the conversion rate of primary bile acids to secondary and lower their carcinogenic potential)

• improved bio availability and increased mineral uptake in intestine

• modulation of immune response (produce number of pro inflammatory cytokines and express the number of receptors on B and T-lymphocytes and macrophages required for initiation of immune response)

• Fiber does not bind to minerals and vitamins and

therefore does not restrict their absorption, but

rather evidence exists that fermentable fiber

sources improve absorption of minerals,

especially calcium. Some plant foods can reduce

the absorption of minerals and vitamins like

calcium, zinc, vitamin C, and magnesium, but

this is caused by the presence of phytate (which

is also thought to have important health

benefits), not by fiber.

Adverse effect of fiber• Intake of dietary fiber in excess of 50 grams per day may

cause an intestinal obstruction in susceptible individuals. In most individuals, however, this amount of fiber will improve (rather than compromise) bowel health.

• Excessive intake of fiber can also cause a fluid imbalance, leading to dehydration. Individuals who decide to suddenly double or triple their fiber intake are often advised to double or triple their water intake for this reason.

• In addition, excessive intake of nonfermentable fiber, typically in supplemental form, may lead to mineral deficiencies by reducing the absorption or increasing the excretion of minerals, especially when mineral intake is too low or when mineral needs are increased such as during pregnancy, lactation, or adolescence.

Drug-Nutrient Interactions

• Dietary fiber, especially the fiber found in fruit, beans, and oat bran, reduces the absorption of a class of cholesterol-lowering medications called HMG-CoA reductase inhibitors (for example, lovastatin) by binding to the drug in the gastrointestinal tract.

• Dietary fiber decreases the absorption of hydralazine, digoxin, and lithium.

• Diets high in dietary fiber may improve glucose control in people with type 2 diabetes, thereby reducing the dose of insulin or oral glucose lowering medications needed to control blood sugar.

• Certain medications, including pain medications (for example, codeine) and calcium channel blockers (for example, verapamil) can cause constipation.

• Increased intake of dietary fiber can reduce the constipation caused by these medications.

Safe level of total fiber

consumptionAI for Children

• 1–3 years 19 g/d

• 4–8 years 25 g/d

AI for Boys

• 9–13 years 31 g/d

• 14–18 years 38 g/d

AI for Girls

• 9–13 years 26 g/d

• 14–18 years 26 g/d

AI for Men

• 19–30 years 38 g/d

• 31–50 years 38 g/d

• 51–70 years 30 g/d

• > 70 years 30 g/d

AI for Women

• 19–30 years 25 g/d

• 31–50 years 25 g/d

• 51–70 years 21 g/d

• > 70 years 21 g/d

Fiber and calories• Because soluble fiber is changed during fermentation, it could

provide energy (Calories/kilojoules) to the body. As of 2009 nutritionists have not reached a consensus on how much energy is actually absorbed, but some approximate around 2 Calories (8.5 kilojoules) per gram of soluble fiber.

• Regardless of the type of fiber, the body absorbs fewer than 4 Calories (16.7 kilojoules) per gram of fiber, which can create inconsistencies for actual product nutrition labels. In some countries, fiber is not listed on nutrition labels, and is considered 0 Calories/gram when the food's total Calories are computed. In other countries all fiber must be listed, and is considered 4 Calories/gram when the food's total Calories are computed (because chemically fiber is a type of carbohydrate and other carbohydrates contribute 4 Calories per gram). In the US, soluble fiber must be counted as 4 Calories per gram, but insoluble fiber may be (and usually is) treated as 0 Calories per gram and not mentioned on the label.

RESISTANT STARCH

• RS1 – native starch inaccessible to α-amylase

• RS2 – native starch accessible to α-amylase by gelatinization

• RS3 – retrograded starch formed during cooking, cooling, extruding the starchy foods

• RS4 – chemically modified starch (starch esters, starch ethers and cross bonded starches

Points to remember for healthy

life style

• Stop eating fast food

• Drink plenty of water (2-3 liters per day)

• Eat your food slowly

• Eat 3 main meals and 2 small meals per day

• Eat vegetables first in each meal

• Make last meal 3 hours before bed time

• Try to do exercise at least 20 minutes per day

With healthy practices and

sustain the ecosystem

T H A N K

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