Fiber

Question 1

What is fibre?

Answer 1

• non-digestible portion of plants
• animal fibre -> collagen and keratin
• food additives
  Plant cell wall = 95% of dietary fibres
• primary and secondary wall
• cellulose and hemicellulose
• lignin -> structural support
• pectins -> intracellular cement, btw and around the cell walls

Question 2

Dietary fibre

Answer 2

consists of non-digestible carbohydrates and lignin that are intrinsic and intact in plants

Question 3

Functional fibre

Answer 3

consists of isolated, non-digestible carbohydrates that have beneficial physiological effects in humans

Question 4

Cellulose

Answer 4

• dietary and functional fibre
• B 1-4 linked glucose units
• main component of plant cell walls
• water-insoluble
• poorly fermented by colonic bacteria
• ex. bran, legumes, nuts, peas, root veggies

Question 5

Hemicellulose

Answer 5

• dietary fibre; component of cell walls
• B 1-4, a 1-2; a 1-3 glycosidic bonds
• sugars in side chains determine characteristics
• water soluble or insoluble
• fermentability varied

Question 6

Pectin

Answer 6

• a 1-4 galacturonic acid
• dietary and functional fibre
• part of plant cell wall
• water soluble with ion-binding potential, gel-forming
• completely metabolized by bacteria
• citrus fruits

Question 7

Ligning

Answer 7

• phenol units
• dietary and functional fibre
• a structural component of plants
• insoluble in water, poorly fermented
• metabolized or enterolactone
• strawberry

Question 8

Gums

Answer 8

• B 1-3 galactose, B 1-6 galactose
• dietary and functional fibre
• secreted at the site of plant injury
• water double and highly fermented by bacteria
• uses as a gelling, thickening agent
• oatmeal, barley

Question 9

Beta-glucans

Answer 9

• B-D-glucopyranosyl (B 1-4 and 1-3 linkages)
• dietary and functional fibre
• water-soluble
• reduce serum cholesterol, postprandial blood glucose
• highly fermentable
• forms viscous gels w/in the GI tract
• oat products

Question 10

Resistant Starch (RS)

Answer 10

• cannot be easily enzymatically digested and absorbed by humans
  RS1 = whole or partially milled grains and seeds
  RS2 = potato, unripe banana, maize, some legumes ‘
  RS3 = cooked/cooled starchy foods (growth of beneficial bacteria, improved glycemic response)
  RS4= chemical modification of starch

Question 11

Fructans

Answer 11

(insulin, oligofructose, fructooligosaccharides)
- fructose units
Promotes growth of bifidobacteria (prebiotic)
- Dietary fibre
- artichokes, onions, chicory, wheat

Question 12

Chitin and Chitosan

Answer 12

• B 1-4 glucose units
• insoluble functional fibre
• bind dietary lipids in the stomach
• binds unesterified cholesterol and phospholipids promoting their exception in the feces
• reduce serum cholesterol
• immune enhancing function

Question 13

Psyllium

Answer 13

• binds water = adds viscosity
• function fibre
• promote a reduction in serum lipids

Question 14

What are the major physiological effects of fibre?

Answer 14

1. Some fibres form a gel:
   - delay and lower nutrient absorption
   - earlier satiation
2. other fibres
   - speed up and digestion

Question 15

What are the factors affecting physiologic and metabolic properties?

Answer 15

1. Solubility in water
2. Water Holding Capacity
3. Adsoprtion or binding ability
4. Degradability or fermentability

Question 16

Solubility in water

Answer 16

Soluble:
- delay gastric emptying
- inc., transit time (slower movement)
- dec., nutrient absorption

Insoluble:
- inc. fecal bulk
- dec. transit time (speed up movement)
- dec., of nutrient absorption

Question 17

Water Holding Capacity

Answer 17

the ability of fibre to bind water as it moves through the GI tract
- describes how much fibre can act as a sponge
Impact:
- pH of GI tract/bolus/chyme
- size of particle
- level of food processing
1. delayed gastric emptying
- slows down movement
2. Reduced missing chyme with digestive enzymes
- gel acts as a ‘physical barrier’ preventing digestive enzymes from assessing the foods
3. Reduced enzyme function
4. Decreased nutrient diffusion
- thickness of the water layer on the surface of enterocytes
- dec. peristaltic movements
5. transit time

Question 18

Adsorption or binding ability

Answer 18

ability to bind inorganic and organic molecules, for ex., enzymes or nutrients
A. Diminish absorption of lipids
- Type of fibre: soluble fibres
- interact w/ fatty acids, cholesterol, bile acids -. prevents the formation of micelles
B. Increased fecal bile exertion
- Type of fibre: soliuble fibre
- absorbs bile acids preventing recirculation and use of formation of micelles
C. lowered serum cholesterol concentration
- Type of fibre: Psyllium, B-glucans
- 1) inc., bile/cholesterol exertion -. dec. cholesterol in the liver -> more LDL
- 2) bile commotion changes -> inhibits HMG CoA reduction -> synthesis of cholesterol
- 3) production of short-chained fatty acids -> inhibits cholesterol and fatty acids synthesis
D. Altered mineral, carotenoid, and phytochemical
- Type of fibre: hemicellulose, pectins, gums,
- enhance or inhibits mineral absorption -> degree of fermentatively
- slows fermentable fibre -> inhibitory effect
- rapidly fermentable -. enhancing effect