Fiber

Health Benefits of Fiber-Diabetes

*Inverse association between dietary fiber intake and risk of developing Type 2 Diabetes *Diets high in fiber are associated with improved glycemic control in people with diabetes or prediabetes. *Ingestion of fiber supplements or foods rich in viscous gel forming fibers improve glycemic control through reduced rates of glucose absorption and insulin secretion. *Improvements are observed with fiber intake of at least 30 grams per day.

Foods Rich in Water-Soluble Fibers

*Legums *Oats *Barley *Rye *Chia *Flaxseeds *Most fruits *Some vegetables *Cooked and cooled pasta, rice and potatoes

Fermentable Insoluble Fibers

*Lignin *Hemicelluloses

Constipation

*Long transit time *Difficult stool expulsion *Low stool output *Incomplete rectal emptying *Best treated with non fermentable fibers

Bifidobacterium and Lactobacillus

*Main bacterial species associated with health and well-being in humans

Where Fermentation Occurs

*Mainly in upper colon *By the cecum and ascending region of colon

Solubility in Water

*Not all soluble fibers alter nutrient absorption *Focus has shifted to viscosity and fermentability when classifying fibers

Gum Sources

*Oatmeal *Barley *Legumes

B-Glucan Sources

*Oats *Barley

Flavonoids

*Organic, bioactive, polyphenolic secondary metabolites *Occur in small quantities in a wide variety of plants

Effective LDL Lowing Quantities

*Pectin - 12 to 24 g *Guar gum - 9 to 30 g *Barley B-glucan - 5 g *Methylcellulose - 5 g *Psyllium - 6 g *Oat B-glucan - 6 g

Viscous Gel Forming Fibers

*Pectins *B-Glucans *Mucilages (psyllium) *Gums

Longer Chain Water-Soluble Fibers

*Pectins *Gums *Inulin *Resistant Starches *Wheat dextrin

Longer-Chain Fiber Fermentation

*Pectins *Inulin *Resistant Starch *Gums

Mucilages

*Plant polysaccharides *Structure similar to gums *Found in seeds of a variety of plants *Includes flax and psyllium

Polydextrose

*Polysaccharide consisting of glucose and sorbitol units that have been polymerized at high temps and under a partial vacuum *Added to foods as a bulking agent or as a sugar substitute *Partly fermentable by colonic bacteria

Health Benefits of Fiber

*Positive effects on: *CVD *Diabetes *Appetite *Satiety *Weight Control *Gastrointestinal Disorders

Galacturonic Acid

*Primary constituent of pectin's backbone *Unbranched chain of a (1-4) linked D-galaturonic acid units

Intermediately Soluble Fibers

*Psyllium *B-glucans *Some hemicelluloses and pectins

Functional Fiber (examples)

*Psyllium (a mucilage) *All dietary fibers except hemicellulose, fructans and lignin.

Shorter-Chain Fermentation

*Rapidly and almost completely fermented by bacteria in colon *frucotooligosaccharides and galactooligosaccharides

Viscosity

*Related to fiber's ability both to bind or hold water and form a gel within the digestive tract. *Most fibers are strongly hydrophilic *Not all fibers form a viscous gel *Viscosity and fermentability are most associated with health benefits

Fiber in Plants

*Rye and barley contain more fiber than other grains *Fruits and vegetables provide almost equal quantities of cellulose and pectin; some hemicellulose and fructans in selected fruits. *Legumes are fiber-rich containing cellulose, hemicellulose, pectins, gums, galactooligosaccharides and resistant starches.

Fructans

*Sometimes called polyfructose *Incudes inulin, oligofructose and fructooligosaccharides. *Composed of fructose units in chains of varying lengths *Water soluble *Highly fermentable *Do not form viscous gels

RS2

*Starch that resists digestion because it is tightly packaged inside of granules within foods *Ungelatinized starch granules *Prevalent in raw or uncooked foods; unripe bananas, potatoes, some legumes and maize. *Dietary fiber

RS4

*Starch that results from chemical modifications of starch *Found in some corn based products. *Functional fiber *Partially fermented by colonic bacteria

Chitin

*Straight chain polymer *Contains B (1-4) linked glucose units *Similar in structure to cellulose; N-acetyl amino group substituted for the hydroxyl group at carbon 2 of glucose. *Component of the exoskeleton of insects; found in shells of crabs, shrimp and lobsters *Insoluble in water *Can adsorb dietary lipids *Promote excretion of lipids in feces

Prebiotics

*Substances that are not digested by human digestive enzymes *Provide health benefits to the host by acting as substrates for the growth and/or activity of one or more species of healthful bacteria in the colon.

Hemicellulose Side Chains

*Sugars in these confer important characteristics on the hemicellulose *Acids in these are slightly charged and more water soluble *Sugar in these influences fermentability by intestinal bacteria

Health Benefits of Fiber - GI Disorders

*Three disorders: constipation, diverticular disease and colon cancer associated with low fiber intake; IBS associated with specific fibers.

Primary Phenols of Lignin

*Trans-coniferyl *Trans-sinapyl *Trans-p-coumaryl

Oligofructose

*Type of fructan *Dietary fiber

Inulin

*Type of fructan *Dietary fiber *Function as prebiotic

Fructooligosaccharides

*Type of fructan *Functional fiber *Formed from the partial hydrolysis of inulin or synthesized from sucrose by adding fructose *Functions as prebiotics

Wheat Dextrin

*Type of resistant dextrin *Water soluble *Fermentable by colonic bacteria *Shown to enhance growth of healthful bacteria in the colon

RS1

*Type of resistant starch *Physically inaccessible to digestion due to its location within a section of the plant's structure. *Found in whole or partially milled grains and seeds *Dietary fiber

Longer Chain Fibers

*Vary in degree of solubility and fermentability *Subdivided into four groups: soluble/highly fermentable, intermediately soluble/fermentable, insoluble/slowly fermentable, insoluble/nonfermentable

Factors that Effect Physiological Effects and Health Benefits of Fiber

*Viscosity *Fermentability *Solubility *Chain length

Lignin Sources

*Wheat *Rye *Carrots *Flaxseed *Berries

Foods Rich in Insoluble Fiber

*Whole grain products *Bran *Legumes *Nuts *Seeds *Cauliflower *Zucchini *Celery *Green beans *Some fruits

Cellulose (examples)

*Whole grains *Bran *Legume *Peas *Nuts *Root vegetables *Cabbage *Seeds *Apples

Hemicellulose sources

*Whole grains *Nuts *Legumes *Some vegetables and fruits

Recommended Fiber Intake

*25 grams/day for 2,000 cal diet * 14 grams/day per 1,000 cal diet *No TUL established

Polyols

*Hydrogenated carbohydrates or sugar alcohols *Used commercially to replace sugars in some foods *Do not raise blood glucose levels similar to sucrose *Include polyglycitol, sorbitol, xylitol, maltitol, mannitol, isomalt *Found in syrup, mints and gums *Also found naturally in apples, watermelon, plums, peaches and pears. *Absorb water in colon; contributes to laxation *Partially fermentable by colonic bacteria

Health Effects of Ingesting Gel-Forming Fibers

*Increased gastric distension *Delayed gastric emptying *Longer intestinal transit time *Reduced nutrient digestion *Reduced micelle formation *Decreased convective movement of nutrients *Decreased nutrient diffusion rate

2009 WHO Definition for Dietary Fiber

Carbohydrate polymers with 10 or more monomeric units, which are not hydrolyzed by human digestive enzymes and are in foods (intrinsic or intact), or have been extracted from food and have physiological benefits to health or are synthetic or modified and have physiological benefits to health.

Three Criteria for Fiber as Prebiotic

*Ingredient must be able to resist digestion by human enzymes and absorption *Ingredient must serve as a substrate for fermentation by intestinal microorganisms belonging to the human microbiota. *Ingredient must selectively stimulate the growth and/or activity of health promoting intestinal bacteria.

Dietary Fiber (term)

Nondigestible carbohydrates and lignin that are intact and intrinsic in plants.

Food Products That Are Prebiotics

*Fructans *Lactulose *Galactooligosaccharides

Shorter Chain Water-Soluble Fibers

*Fructooligosaccharides *Galactooligosaccharides

Shorter Chain Fibers

*Fructooligosacharides *Galactooligosaccharides *Not digestible *Highly soluble *Fermentable by colonic bacteria

Pectin's Backbone

*Galacturonic acid

Tree Exudates

*Gum arabic *Gum karaya *Gum ghatti

Shrub Exudate

*Gum tragacanth

B-Glucans

*Homopolymers of glucose units *Smaller in size; contain different linkages than cellulose *Water soluble *Highly fermentable by colonic bacteria *Form viscous gels within digestive tract *Used commercially as functional fiber *Effectiveness in reducing serum cholesterol and moderating blood glucose

How Fiber May Prevent Colon Cancer

*Adsorbing and promoting the excretion of primary bile acids, thereby decreasing their free concentration and availability for conversion to more harmful secondary bile acids *adsorbing procarcinogens and carcinogens and/or diluting intestinal contents to minimize carcinogenic compound interactions with colonic mucosal cells *reducing colonic transit time, which in turn decreases the time during which toxins can be synthesized and in which they are in contact with the colonic mucosa cells. *Short chain fatty acids produced during fermentation in the colon decrease the pH within the lumen of the colon

Gums

*Also called hydrocolloids *Dietary and functional fibers *Water soluble; fermentable by colonic bacteria *Secreted at site of plant injury; can be exuded from plants * Composed of sugars and derivatives *Used as food additives and thickening agents

Resistant Dextrins

*Also called resistant maltodextrin *Generated by heating and enzymatically treating starch with amylase *Consist of glucose polymers; contain a variety of glucosidic bonds. *Designated as functional fiber

Pectin Sources

*Apple *Berries *Apricots *Citrus *Legumes *Nuts *Some vegetables

Fermentable Intermediate Solubility Fibers

*B-glucan *Psyllium

RS3

*Called retrograde starch or amylose *Formed with moist heat cooking then cooling of starch that has gelatinized. *Found in cooked and cooled potatoes, rice, pasta, bread and some corn. *Functional fiber; partially fermented by colonic bacteria

Dietary Fiber (examples)

*Cellulose *Hemicellulose *Pectins *Lignin *Gums *B-glucans *Fructans *Resistant Starches

Insoluble Fibers

*Cellulose *Lignin *Some hemicelluloses *Some pectins, resistant starches, chitosan and chitin

Non-Fermentable Fibers in Colon

*Cellulose *Lignin *Some hemicelluloses and resistant starches *Beneficial in promoting laxation *Beneficial in treating constipation by increasing fecal bulk or volume

Fructan Sources

*Chicory *Asparagus *Leeks *Onions *Garlic *Jerusalem artichoke *Tomatoes *Bananas

Diverticular Disease

*Condition characterized by the presence of diverticula in the colon *Diverticula is the protruding or bulging pouches of the wall of the colon

Bran Component of Cereals

*Contain the most fiber (over 95%) *Outer layer consists of primary and secondary cells walls. *Walls are fiber rich, contain strands of cellulose arranged within a matrix of other fibers. *Mostly hemicellulose and pectins *Lesser amounts of fructans, resistant starch and B-glucans.

Orafti

*Contains fructooligosaccharides

*FiberChoice

*Contains inulin

Citrucel

*Contains methylcellulose

Fiberall and Metamucil

*Contains psyllium

Benefiber

*Contains wheat dextrin

Chitosan

*Deacetylated form of chitin *Insoluble in water *Can adsorb dietary lipids *Promote excretion of lipids in feces

Pectin

*Dietary and functional fiber *Heterogeneous polysaccharides *Found in plant cell walls, intercellular regions of plants and in outer skin and rind of some fruits and vegetables. *Water soluble *Gel forming

Cellulose

*Dietary and functional fiber *Long, linear polymer of up to 10,000 B (1-4) linked glucose units *Water insoluble; can be modified chemically *Used as a food additive because modified form can be more soluble in water and more fermentable by colonic bacteria.

Hemicellulose

*Dietary fiber *Consists of a heterogeneous group of polysaccharides *Contain both hexoses and pentoses in backbone (xylose, mannose, galactose) *Side chains are made up of arabinose, glucoronic acid and galactose.

Lignin

*Dietary fiber; may serve as functional fiber *Highly branched polymer of phenol units *Strong intramolecular bonding *Hydrophobic binding capacity *Provides structural support in plant cell walls *Found in bran layer of cereal *Found in stems and seeds of fruits and vegetables *Insoluble in water *Generally not fermented by colonic bacteria

Health Benefits of Fiber-CVD

*Diets high in fiber associated with a reduced risk of death from CVD. *Evidence reported for inverse relationships between fruit and vegetable intake and heart attack and stroke; between intake of whole grains and heart disease. *Intake of several viscous gel forming fibers = lower serum total and LDL concentrations. *Viscous gel-forming fiber trap bile acid and cholesterol within a gelatinous mass; limits micelle formation and absorption enhancing they excretion in feces.

FDA Approved Health Claims

*Diets low in fat and rich in high fiber foods may reduce the risk of certain cancers *Diets low in saturated fat and rich in soluble fiber may reduce the risk of heart disease. *Diet low in total fat, saturated fat, and cholesterol and rich in whole grains and other plant foods may help reduce the risk of heart disease.

Water-Soluble Fibers Solubility

*Dissolve in hot water

Insoluble Fibers Solubility

*Do not dissolve in water

Fermentation of Fiber Provides What?

*Energy *Substances for microbial growth *Products such as short chain fatty acids

Health Benefits of Fiber - Appetite and/or Satiety and Weight Control

*Fiber rich foods have lower energy density and high volume; promotes satiety *Viscous gel forming fibers may promote satiety our to fiber induced delays in gastric emptying and/or alterations of digestive tract hormones (gherkin, glucagon, peptide YY, CCK) *Nonviscous fibers like galactooligosaccharides has been shown to reduce appetite

Six Subclasses of Flavonoids

*Flavonols *Flavanols *Flavones *Flavanones *Anthocyanins *Isoflavones

Psyllium

*From the husk of psyllium seeds *Contains several polysaccharides *Fairly soluble in water *Added to metamucil for its laxative properties

Functional Fiber (term)

Consists of isolated, extracted, or manufactured non digestible carbohydrates that have been shown to have beneficial physiological effects in humans.

Total Fiber

Dietary fiber present within food plus functional fiber that has been added to the food.

Resistant Starch

Starch that cannot be or is not easily enzymatically digested. *Four main types: RS1, RS2, RS3, RS4