Fiber

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Nutrition
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1

What is dietary fiber and functional fiber

Dietary fibre: nondigestible carbohydrates andlignins that are intrinsic and intact in plants.

• e.g. cellulose, pectin, gums, hemicellulose, beta-glucans

Functional fibre: Isolated, nondigestible carbohydrates that have beneficial physiological effects in humans.

• May be isolated or extracted.

• Can be derived from plants or animals

2

Dietary fiber can be isolated from animal and plant sources?

True/False

False

Dietary fiber - plants

Functional fiber - plants or animals

3

What is Crude Fiber?

Crude Fibre - the residue of plants remaining after extraction with dilute acid followed by dilute base and subtracting the ash

DOES NOT INCLUDE PECTINS AND GUMS

4

PECTINS AND GUMS are crude fiber?

True/False

False

Crude fiber - A measurement of fibre content.

5

Crude fibre is the insoluble residue of an acid hydrolysis followed by an alkaline one. This residue contains true cellulose and insoluble lignin.

...

6
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Cellulose

-dietary or functional fiber

-long linear polymer of _____

-with _____ linkage

-water soluble or insoluble?

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Dietary and functional fiber when added to foods

glucose polymer with ß1-4 linkages

insoluble in water

found in plant cells walls

7

Hemicellulose

-dietary or functional fiber

-structure

-soluble or insoluble

card image

dietary fiber and a component of plant cell walls

branched structure of different monosaccharides

generally insoluble, but can be partially soluble

8

The sugars in the side chains confer important characteristics on the hemicellulose.

What are they?

ex: hemicellulose that contain acids in their side chains are slightly charged and water soluble.

Other hemicelluloses are water insoluble

9

Pectins

-dietary or functional

-structure

-dietary and functional fiber

-made up of polygalacturonic acid backbone with possible side chains of other monosaccharides

-water soluble and gel-forming

10

What makes a backbone structure of pectins?

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Galacturonic acid is a primary constituent of pectin and makes up its backbone structure.

11

Pectins are gel-forming

true/false

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True

Pectin is added to jellies and jams to promote gelling.

Rich sources of pectins include apples, strawberries, and citrus fruits.

12

Lignins

-soluble or insoluble

-sources of lignins

-structure

-Insoluble in water, has hydrophobic binding capacity

- found in the woody parts of plants (e.g. in carrots, strawberry seeds). Especially in stems and seeds of the fruits.

- not a polysaccharide

13

-Edible seeds of strawberries is a source of lignin

-Lignin is a polysaccharide

true/false

True

False

14

Gums (e.g. gum arabic, guar, carrageenan) and mucilages (e.g. psyllium)

-structure

-soluble or insoluble; gel forming or not?

-have various monosaccharides

-dietary and functional fiber

-give structure and texture to food

( ex: guar gums are added as thickening agent and water-binding agent to products such as bakery goods, sauces, dairy products, ice creams, salad dressings etc)

-soluble and gel-forming

15

Gums

Gums are secreted at a site of plant injury by specialized secretory cells. Composed of variety of sugars and sugar derivatives.

Within the large intestine, gums are highly fermented by colonic bacterias.

16
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Mucilages (клейкое вещество)

ex

ex: psyllium

products containing psyllium have high water0binding properties and thus provide viscosity in solutions.

17

β-glucans

-source

-water solubility

-gel formation?

- water soluble dietary fiber

-found in relatively high amounts in oats and barley

- gel- forming

- fermentable in colon, reduce serum cholesterol and blood glucose concentratins

18

Chitin, Chitosan

- solubility

- structure. Made of ____ polysaccharides with ____ linkage

- derived from

card image

- chitin is insoluble in water

-made of amino-polysaccharides with β1-4 linkages

– derived from the exoskeleton of insects and shells of crabs, shrimp and lobsters

*chitosan is a deacetylated form of chitin

19

Polydextrose and polyols

- digestible or undigestible???

- polymers of ___

- undigestible polymers of glucose and sugar alcohols (natural or due to processing)

- neither digested nor absorbed by the human GI tract

20

Resistant dextrins

is it fiber?

digestion by GI tract?

- starches that has been treated in a way that makes them indigestible

*generated by treating cornstarch with heat,acid, and enzymes (amylase)

21

Resistant starch

source/digestion

- less digestible or undigestible starch due to processing or due to plant structure

22

Fructans

structure/examples

- fructose polymers

- e.g. inulin, oligofructose

23

**Characteristics of dietary fiber

solubility in water

water-binding capacity or viscosity

ability to bind organic and inorganic molecules

fermentability by intestinal bacteria

24

Fibres in GI tract

stomach

- delays emptying

- gives a feeling of satiety

- increases viscosity

25

Fibres in GI tract

small intestine

- delays absorption of nutrients

- can bind minerals

26

Fibres in GI tract

Large intestine

- attracts water, which softens stool

- increases frequency of defecation

- anaerobic bacteria fermentation degrades fibres to varying degrees

27

Soluble fiber in general DELAY gastric emptying, slows the movement through intestine, and decreases nutrient (glucose) absorption.

ex?

ex: pectins, gums, b- glucans, some hemicellulose

28

Insoluble fibers decrease (speed up) intestinal transit time - speeds the movement through intestine, increase fecal bulk.

ex?

ex: cellulose, some hemicellulose, legnin

29

What does viscosity of fiber means?

ex of fiber that form gels?

ability of fibre to bind water and some fibers form gels

ex: pectins,b-glucans,mucilages,gums

30

Think of fiber as a dry sponge moving though digestive tract hydrating or soaking up the water and digestive juices. ingesting fibers that can hold water and create viscous solutions within the GI tract causes a number of effects:

*delay (slow) emptying of food from the stomach; longer intestinal transit time

*reduced nutrient absorption

31

Delay (slow) emptying of food from the stomach

explain

when fibers form viscous gels, the release of chyme from the stomach into duodenum is delayed (slowed). Thus, nutrients remain in the stomach longer with these fibers, carbs and lipids remain in the stomach undergo No digestion in the stomach and must move to the SI.

32

Reduced nutrient absorption

explain

gums appear to slow glucose absorption by decreasing the movement of glucose within the intestinal lumen. thus

DElAY GLUCOSE ABSORPTION

LOWER BLOOD GLUCOSE CONCENTRATIONS

AFFECT HORMONAL RESPONSE TO THE ABSORBED NUTRIENT ex: reduced insulin secretion

33

why soluble fibers decrease nutrient absorption?

because the nutrients are in contact with enterocytes for too short time.

34

Ingesting fibers with adsoprtion properties causes:

*diminished adsorption of lipids

*increase fecal bile acid extretion

*lowered serum cholesterol concentrations

35

*diminished adsorption of lipids

explain

insoluble fiber can interact with fatty acids, cholesterol, and bile acids.

f.a and cholesterol that are bound or complexed with fiber cannot form a micelles and cannot be adsorbed in bound form. Thus, fiber-boud lipids typically are not absorbed in SI and pass into large intestine where they are excreted in the feces or degraded by intestinal bacteria,

36

Fermentability of fiber in the large intestine

Fermented fibers vs Non-or less fermentable fibers

Fermentable (pectins,gums,psyllium,resistant starch)

*promote growth of bacterial population which

* increase fecal mass and

* generate short-chain f.a. for use by the body

37

Fermentable fibers

explain benefits to the body

some fibers have been shown to function as a prebiotic (probiotics are foods that contain live cultures of bacteria)

however,

They must be able to survive passage through the GI tract and colonize the colon

• The most common are lactic acid bacteria such as Lactobacillus acidophilus and L. casei

• The most common source is fermented dairy (e.g. yogurt)

38

what are prebiotics?

Prebiotics are food ingredients that stimulate the growth of beneficial bacteria and promote health (e.g. fibre)

39

probiotic vs prebitotic

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Prebiotics are food ingredients that stimulate the growth of beneficial bacteria and promote health (e.g. fibre)

Probiotics are foods that contain live cultures of bacteria

40

Fermentability of fiber in the large intestine

Fermented fibers vs Non-or less fermentable fibers

Non-or less fermentable fibers

(cellulose and lignin/slow fermentable hemicellulose)

*increase water-holding capacity

*greater frequency of defecation (increase fecal volume or bulk)

41

fecal bulk increases as ____

as fiber fermentability decreases

42

DRI for fiber

name 5 criteria

1. Effect on lowering blood lipids and blood pressure and reducing risk of heart disease (this one was used to set the DRI for fibre)

2. Effect on GI health

3. Effect on colon cancer

4. Effect on glucose tolerance, insulin response, and amelioration of diabetes

5. Effect on satiety and weight maintenance

3,4,5 had insuffisient evidence to set DRI

43

1. Effect on lowering blood lipids and blood pressure and reducing risk of heart disease (this one was used to set the DRI for fibre)

DRI criteria explain

*protection against cardiovascular disease

* viscous gel-forming fibres trap bile acids and cholesterol in GI tract, limiting micelle formation and absorption

44

2. Effect on GI health

explain

*short-chain fatty acids - energy source for intestinal cells (metabolites of fermentable fibers are lactate and short-chain fatty acids)

* biotin and other nutrients (vitamin K) produced by bacteria

*relieves constipation, promotes laxation

*reduces risk of appendicitis, diverticular disease, hemorrhoids, duodenal ulcers

45

3. Effect on colon cancer

explain

* insuffisient evidence to set DRI

  • reduces pH of LI, which reduces formation of secondary bile acids, promotes good bacteria, increases mucin production

• promotes butyrate formation, which promotes health of colon cells

• binds to or dilutes procarcinogens and carcinogens

• reduces exposure time to carcinogens by speeding up transit

46

Butyric acid appear to slow the proliferation and differentiation of colon cancer cells

true/false

True

Highly-fermentable fiber residues, such as those from resistant starch, oat bran, pectin, and guar are transformed by colonic bacteria into short-chain fatty acids (SCFA) including butyrate, producing more SCFA than less fermentable fibers such as celluloses.

47

4. Effect on glucose tolerance, insulin response, and amelioration of diabetes

3,4,5 had insuffisient evidence to set DRI

  • may help with weight control
  • slows glucose absorption
48

5. Effect on satiety and weight maintenance

3,4,5 had insuffisient evidence to set DRI

  • fibre rich foods have lower energy density which can promote satiety
  • possible effect on satiety inducing hormones such as ghrelin
49

Fiber recommendations

...

50

Average Canadian Intake of fiber __g

14 g

51

AI for men __ g/day

AI for women __g/day

(19-50 years)

men 38 g/day

women 25 g/day

52

Foof health claim definition

Any representation on labeling or advertising that states, suggests or implies that a relationship exists between consumption of a food or an ingredient and a person’s health

53

Acceptable function claims related to fibre

consuming a serving of a product containing or providing __ grams of fibre from ___ promotes ____ or _____

consuming a serving of a product containing or providing 7 grams of fibre from coarse wheat bran promotes laxation or regularity

54

Acceptable function claims related to fibre

consuming a serving of a product containing or providing ___ grams of fibre from____ promotes ____ or ____

consuming a serving of a product containing or providing 3.5 grams of fibre from psyllium seed promotes laxation or regularity

55

There is no UL for total fiber

Dietary fiber appears to be tolerated up to __ g/day in vegetarians

80 grams/day

56

Dietary fibre (total fibre and fibre found infruits and vegetables as well as whole grains) and decreased risk of colorectal cancer

True/False

more false

no longer convincing evidence