1. Chapter 4
Fiber
2009 Cengage-Wadsworth

2. Definitions of Dietary Fiber & Functional Fiber
Dietary fiber - nondigestible CHO & lignin that are intact & intrinsic in plants
Functional fiber - nondigestible CHO that are isolated, extracted, or manufactured & known to have physiological benefits
2009 Cengage-Wadsworth

3. Fiber and Plants >95% of fibers from cell wall
Primary wall
Secondary wall
Fiber-related components
Cellulose
Hemicellulose
Lignin
Pectins
Suberin
Cutin
2009 Cengage-Wadsworth

4. Chemistry & Characteristics of Dietary & Functional Fibers
Varieties:
Cellulose
Hemicellulose
Pectins
Lignin
Gums
-glucans
Fructans
Resistant starch
Chitin & chitosan
Polydextrose & polyols
Psyllium
Resistant dextrins
2009 Cengage-Wadsworth

5. Cellulose Dietary & functional fiber
Long, linear polymer of  1-4 linked glucose units
Main component of plant cell walls
Sources: bran, legumes, nuts, peas, root vegetables, cabbage family, outer covering of seeds, apples
2009 Cengage-Wadsworth

6. Hemicellulose Dietary fiber
Heterogenous group of polysaccharide substances
Sugars in backbone & side chains
Xylose, mannose, galactose (backbone)
Arabinose, glucoronic acid, galactose (side chains)
Sources: bran, whole grains, nuts, legumes, some vegetables & fruits
2009 Cengage-Wadsworth

7. Pectins Dietary & functional fiber
Complex group of polysaccharides called galacturonoglycans
Backbone = galacturonic acid
Cell wall & middle lamella in plants
Water-soluble, gel-forming
Sources: apples, strawberries, citrus
2009 Cengage-Wadsworth

8. Lignin Dietary & functional fiber
Highly-branched polymer composed of phenol units with strong bonding
Structural components of plants - found in stems, seeds, bran layer
Sources: wheat, mature root vegetables, fruits with edible seeds
2009 Cengage-Wadsworth

9. Gums (Hydrocolloids) Dietary & functional fibers
Group of substances secreted at site of plant injury
Tree exudates: gum arabic, gum karaya, gum ghatti
Shrub exudate: gum tragacanth
Composed of sugars & derivatives
Sources: oatmeal, barley, legumes
2009 Cengage-Wadsworth

10. -Glucans Dietary & functinal fibers
Homopolymers of glucopyranose units
Water-soluble, highly fermentable
Sources: cereal brans, especially oats & barley
2009 Cengage-Wadsworth

11. Fructans--Inulin, Oligofructose, & Fructooligosaccharides
Dietary fibers
Fructose units in chains of varying length
Prebiotics
Sources: chicory, asparagus, onions, garlic, artichokes, tomatoes, bananas
2009 Cengage-Wadsworth

12. Resistant Starch Starch that cannot be digested by humans Types
RS1 - plant cell walls
RS2 - ungelatinized starch granules
RS3 - retrograde starch from cooking & cooling or extruding foods
RS4 - chemically modified starch
RS1 & RS2 = dietary fibers, RS3 & RS4 = functional fibers
2009 Cengage-Wadsworth

13. Chitin & Chitosan Chitin Chitosan
Amino-polysaccharide polymer containing  1-4 linked glucose units
Cells walls of some lower plants
Chitosan
Deacetylated form of chitin; polysaccharide made of glucosamine & N-acetyl glucosamine
2009 Cengage-Wadsworth

14. Polydextrose & Polyols
Polysaccharide of glucose & sorbitol units that have been polymerized at high temperatures & partial vacuum
Polyols
Polyglycitol & malitol
Found in syrups
2009 Cengage-Wadsworth

15. Psyllium Functional fiber Mucilage from husk of psyllium seeds
Used as laxative
Must ingest plenty of fluids
2009 Cengage-Wadsworth

16. Resistant Dextrins Functional fibers
Generated by treating cornstarch with heat & acid & then with amylase
Glucose polymers containing  1-4 &  1-6 glucosidic bonds &  1-2 &  1-3 bonds
2009 Cengage-Wadsworth

17. Selected Properties & Physiological Effects of Fiber
Important properties include:
Solubility in water
Water-holding capacity & viscosity
Adsorption or binding ability
Degradability/fermentability
2009 Cengage-Wadsworth

18. Solubility in Water Classifications:
Soluble - dissolve in hot water
Insoluble - don’t dissolve in hot water
Water-soluble: some hemicelluloses, pectin, gums, -glucans
Water-insoluble: cellulose, lignin, some hemicelluloses, chitosan, chitin
2009 Cengage-Wadsworth

19. Solubility in Water Soluble Insoluble Delay gastric emptying
Increase transit time
Decrease nutrient absorption
Insoluble
Decrease transit time
Increase fecal bulk
2009 Cengage-Wadsworth

20. Water-Holding/Hydration Capacity & Viscosity
Ability of fiber to bind water
Delayed (slowed) gastric emptying
Reduced mixing of gastrointestinal contents with digestive enzymes
Reduced enzyme function
Decreased nutrient diffusion rate--attenuation of the blood glucose response
Altered small intestine transit time
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21. Adsorption or Binding Ability
Diminished absorption of lipids
Increased fecal bile acid excretion
Lowered serum cholesterol concentrations (hypocholesterolemic properties)
Altered mineral & carotenoid absorption
2009 Cengage-Wadsworth

22. Degradability/Fermentability
Fermentable fibers
Fermentable fibers as prebiotics
Short-chain fatty acid generation
Increased water & sodium absorption in the colon
Mucosal cell proliferation
Provision of energy
Acidification of luminal environment
2009 Cengage-Wadsworth

23. Degradability/Fermentability
Nonfermentable fibers
Detoxification
Increased fecal volume (bulk)
2009 Cengage-Wadsworth

24. Roles of Fiber in Disease Prevention & Management
Hypoglycemic & hypolipidemic effects of soluble fibers
For diabetes & high serum cholesterol
Insoluble, nonfermentable fibers for GI diseases
Diverticular disease, gallstones, IBS, constipation
Health claims for fiber
2009 Cengage-Wadsworth

25. Roles of Fiber in Disease Prevention & Management
Mechanisms
Adsorb bile acids, promote excretion
Increase fecal bulk
Provide fermentable substrates for bacteria in colon
Shortened fecal transit time
Decreases interluminal pH
Fermentation may release fiber-bound calcium
Butyric acid appears to hinder cancer cells
Insoluble fibers bind carcinogens
2009 Cengage-Wadsworth

26. Recommended Fiber Intake
Adequate Intakes
Adults:
19-50: 25 g for women, 38 g for men
51 or >: 21 g for women, 31 g for men
Children:
1-3: 19 g; 4-8: 25 g
Girls 9-18: 26 g
Boys 9-13: 31 g; boys 14-18: 38 g
2009 Cengage-Wadsworth

27. Phytochemicals & Herbal Supplements in Health & Disease
Perspective 4
Phytochemicals & Herbal Supplements in Health & Disease
2009 Cengage-Wadsworth

28. Phytochemicals & Herbals
Echinacea
Garlic
Ginkgo biloba
Ginseng
Milk thistle
St. John’s wort
Regulation of herbal supplements
2009 Cengage-Wadsworth