Chapter 5- Fiber

chitosan

deacetylated form of chitin polysaccharide made of glucosamine and n-acetyl glucosamine help joint health

diverticulitis

inflammation of pouches lower fiber diet

frutans:

inulin, oligofructose & fructooligosaccharides

chitin and chitosan

popular in 90s, know to reduce cholesterol

nonfermentable fibers

primary cellulose and lignin, some hemicellulose detoxification increased fecal volume/bulk

four properties of fiber

solubility water-holding capacity/viscosity adsorption or binding ability degradability/fermentability

types of resistant starches

RS1- plant cell walls RS2- ungelatinized starch granules RS3- retrograde starch from cooking and cooling or extruding foods RS4- chemically modified starch

pectins, gums, oat and wheat bran, psyillium degraded to

SCFA: acetic acid, butyric acid, propionic acid also produce H+, CO2 and methane gases smell depends on composition dif fibers fermented to dif SCFA by different bacteria

oligosaccharides

act as fiber residues of non-digested portion stays in gut and is fermented by bacteria

fiber and plants

all fiber from plant cells plant cell wall-contains 99% of dietary fiber

chitin

amino polysaccharide polymer containing beta 1-4 linked glucose units cell walls of some lower plants abundant in the shell of crabs, shrimp, lobsters functional-non edible

food sources of pectin

apples, strawberries, citrus fruits can be used to make fruit jams and jellies

side chain of hemicellulose

arabinose, glucoronic acid, galactose determines solubility (can be either) acidic- more soluble neutral- insoluble

lignin as plant matures

as plants mature- spreads thru intracellular spaces, invading the pectic substances eventually permeates both primary and secondary walls as plant development continues- suberin and cutin secreted

increased fecal bile acid excretion

bile acids bound to fibers cannot form micelles and therefore and excreted in feces- disconnect enteropatic circulation

adsorption meaning

binding ability

cellulose sources

bran, legumes, nuts, peas, root vegetables, cabbage family, outer covering of seeds, apples

sources of hemicellulose

bran, whole grains, nuts, legumes, some vegetables and fruits

pectinase

breaks down linkage between galacturonic acids in backbone --> mucous pectins become watery

gums (hydrocolloids)

dietary and functional fibers substances secreted at plant injury-oozes out composed of sugar and sugar derivatives extracted and used to make liquid more thick/viscous ready digested by colonic bacteria water soluble heteropolysaccharide

hemicellulose

dietary fiber in cell wall heteropolysaccharide

RS1 & RS2

dietary fibers

fructans

dietary fibers/ functional powdered forms fructose units in chains of varying length prebiotics

water soluble

dissolve in hot water some hemicelluloses, pectin, gums and beta glucans delay gastric emptying increase transit time decrease nutrient absorption absorbs water, becomes slimy slows chyme movement- higher satiety

soluble fiber

dissolve well in water pectin, gums, beta glucans, and some hemicelluloses

insoluble fiber

don't digest in water lignin, cellulose, some hemicelluloses

insoluble in water

don't dissolve in hot water cellulose, lignin, some hemicelluloses, chitosan, chitin decreased transit time- quick movement increased fecal bulk- bc fibrous residue crude sponge- holds water but doesn't dissolve

decreased nutrient diffusion rate WHC

due to increased viscosity of the unstirred water level gums slow glucose, amino acid and fatty acid absorption by decreasing the convection currents caused by peristalsis delay glucose absorption, lower blood glucose concentrations, and affect hormonal increase nutrients may "miss" normal site of maximum absorption so lower amounts absorbed

detoxification

increased healthy microbial cells result in increased microbial scavenging and sequestering of toxins certain colonic bacteria appear to inhibit tumor cell division and delay tumor formation L acidophilus reduced enzyme activity that converts procaricinogens to carcinogens--decrease enzymes that activate carcinogens

effects of SCFA

increased water and sodium absorption in the colon by Anti diuretic hormone, etc this absorption stimulates water and sodium absorption in the colon mucosal cell proliferation provision of energy provide calories- about 10-15% cho fermented in colon

lignin and resistant dextrins

known to have significant physiologic effect in body so used as functional fiber in additives

adsorption

ligninin (insoluble), gums, pectins, and hemicellulose (soluble) can bind enzymes and nutrients diminished absorption of lipids increased fecal bile acid excretion, lowered serum cholesterol, altered mineral balance--don't absorb so excreted feces

similarities btw amylose vs cellulose

linear form plant sources homopolysaccharides

mucilages

made by plant sector cells to protect seed endosperm from desiccation (drying out)

suberin

made of phenolic compounds, alcohols and acids enzyme and acid resistant wax coating hydrophobic

degradability or fermentability

many different kinds of bacteria can degrade fibers- 4 lb in gut especially pectins, gums, mucilages, algal polysaccharides, soluble=more fermentable some cellulose and hemicellulose- slower bc insoluble fermentable fibers produce lactate and SCFA

psyllium

metamucil- stool softener functional fiber mucilage from husk of psyllium seeds used as laxative *must ingest plenty of fluids-- or will cause constipation

ability of fibers to lower serum cholesterol levels based on

more bile acid excreted, cholesterol is used to make more bile acids instead of causing problems in blood vessels shift from chalk toward chenodexycholic acid production of propionate from bacteria has been shown to lower cool conc in animals thru fermentation

dietary fiber

nondigestible CHO and lignin that are intact and intrinsic in plants come from food sources

functional fiber

nondigestible CHO that are isolated, extracted, or manufactured and known to have physiological benefits powder/liquid forms

sources of gums

oatmeal, barley legumes

high water-holding capacity fibers

pectins, gums, some hemicellulose act as sponges, absorbing water and digestive juices from the GI tract and from viscous solutions within GI tract

dietary fiber definition

plant polysaccharides and lignin which are resistant to hydrolysis by the digestive enzymes of man

diverticular disease

pouches on colon--> herniea fecal matter stay in pouches and cause issues high fiber diet helps

reduced mixing of GI contents with digestive enzymes WHC

presence of viscous gels or hydrated fiber provides a physical barrier that can impair the ability of nutrients to interact with digestive enzymes inhibits availability of water for hydrolysis-enzymes need water to break things down

where are pectins found

primary cell wall and the middle lamella

potential to lower cholesterol

psyllium, guar, oat gum, pectin oat bran, soybeans- intermediate effect corn, wheat, rice bran- no effect fruit and veggies- lower

RR

relative risk

microfibrils

several cellulose units holding themselves together by hydrogen bonds --> fibrils--> plant cell walls

mucilages & algal polysaccharides

similar to gums in chem structure hydrophilic make good stabilizers both can be degraded by colonic bacteria

roles of fiber in disease management

soluble fibers hypoglycemic and hypolipidemic effects for diabetes and high serum cholesterol insoluble/nonfermentable fibers for diverticular disease

diminished absorption of lipids

soluble fibers and lignin can bind to fatty acids, cholesterol and bile acids fiber bound lipids are not absorbed in the si excreted in feces or degraded by intestinal bacteria

controversial topics

soluble fibers can increase risk of colon cancer evidence of fiber reducing colon cancer meta-analyses of epidemiological and case control studies have found that high fiber diets are protective against colon cancer

why does beta gluons lower cholesterol

soluble fibers easily bond to nutrients reduce lipid absorption accelerate secretion of bile acids that require cholesterol to be made in liver

side chains of pectins

sometimes attached to rhamnose, arabinose, xylose, and fucose

primary plant cell wall

thin envelope surrounding contents of growing cell soft part

pectins and ripeness

unripe= pectinic acid ripe= pectine over ripe= pectic acid (can't form gel)

lignin

very insoluble in water dietary and functional fiber noncarbohydrate component--doesn't even look like CHO highly-branched polymer composed of phenol units with strong bonding not digestible by colonic bacteria- bc contains phenol units structural components of plants

cellulose

water insoluble dietary & functional fiber long, linear beta 1-4 linked glucose--homopolysaccharide hydrogen bonds btw cellulose chains produce microfibrils poorly fermented by colonic bacteria--bulky residues in fecal matter

delayed gastric emptying by WHC

when fibers form gels within stomach, the release of chyme from stomach to intestine is delayed--mucus layer on brush border creates increased satiety, decreased hunger slows down digestion process

acidification of Luminal environment

with a lower pH, bile acids become less soluble--fecal matter calcium is able to bind bile and fatty acids shown to reduce the risk of colon cancer

backbone of hemicellulose

xylose, mannose, galactose

recommended intake of fiber

20-40 g/day fiber 35 upper limit excessive insoluble fiber intake is not recommended for people in negative mineral balance -infants, children, adolescents (female), pregnant women -can be detrimental to Ca, Zn, Fe balance if intake is marginal

how much fiber recommended per day

28-35 g

fiber & preventing colon cancer

35 g/day reduce risk by 40% than just 15 g

provision of energy

butyric acid- used by colonic epithelial cells propionic and acetic acids taken to liver for metabolism skeletal and cardiac muscles can metabolize acetate

hemicelluloses

can be either soluble or insoluble bc depends composition of carbohydrates and their side groups

resistant starch

can't be digested by humans

plant cell wall

cellulose, hemicellulose, lignin, pectin consists of both primary and secondary wall composition changes as it grows

differences btw amylose vs cellulose

cellulose- beta 1-4, skin of fruit and veg as fiber amylose- alpha 1-4, meat of grains and root veggies as starch, digested easily in GI

sources of beta glucans

cereal brans, especially oats and barley

sources of fructans

chicory, asparagus, onions, garlic, artichokes, tomatoes, bananas

increased fecal volume

consists of unfermented fiber, salts, water, bacterial mass--50% feces bacterial mass is 80% water, so softens stools antibiotics kill bacteria in gut--heart stool reduced intestinal transit time decreased intraluminal pressure--increase smooth fecal bulk

fermentation of beta glucans

cook oatmeal--> gummy substance dissolved in water making in gel like

how does water soluble fiber decrease nutrient absorption

creates a barrier between nutrients and brush border (glucose is an example)

pectin as plant matures

decreases as plants mature intracellular cement located between and around cell walls

water-holding capacity

decreases glycemic index decreases gastric emptying increases viscosity of chyme pH, size of fiber particles, degree of food processing can also influence capacity

algal polysaccharides

derived from algae and seaweed carageenan and agar-- used for thickeners, in asian culture used for jellies

secondary plant cell wall

develops as cell matures, consists of cellulose arranged in an orderly pattern hard part fruit becomes older, makes more so becomes harder

pectins

dietary and functional fiber complex group of polysaccharides called galacturonoglycans water soluble gel forming can be broken down by colonic bacteria fermented in large intestine--causes gas

beta glucans

dietary and functional fibers homopolymers- glucopyranose water soluble highly fermentable known to lower cholesterol levels

phenol

extremely insoluble in water, increases volume of fecal matter

dietary recommendations

fiber-rich legumes at least 5 servings of f&v/d 2-3 whole grain servings/d

altered mineral balance

fibers containing ironic acid hemicellulose, pectins, gums can form bridges with minerals in the GI tract lignin can also bind minerals slowly fermentable fibers can decrease mineral absorption rapidly fermentable fibers (pectins) can increase Ca, Zn, Fe absorption in- make acid in gut

cutin

found on external surface of cell wall impermeable to water enzyme and acid resistant wax coating hydrophobic

inulin

fructans with a lot of glucose

FOS

fructose oligosaccharides

RS3 & RS4

functional fibers

resistant dextrins

functional fibers (glucose polimers) treatment of cornstarch with heat, acid, and with amylase shorter length of chemical structures than resistant starch alpha 1-4, alpha 1-6, alpha 1-2, and alpha 1-3 glucosidic bonds

sugars composing gums

galactose, ironic acids, arabinose, rhamnose, mannose mostly soluble in water

backbone of pectins

galcturonic acid

tree exudates

gum arabic, gum karaya, gum ghatti

shrub exudate

gum tragacanth

liginin

has non carbohydrate forms with insoluble phenol rings

colon cancer

high bile acid concentrations associated with colon cancer high pH=negative effect on gut fibers that absorb bile acids and promote excretion reduce colon, also prevents primary bile acids from converting to secondary bile acids secondary bile acids are thought to promote carcinogenesis make environment better for good bacteria

sources of lignin

husks, wheat, mature root vegetables, fruits with edible seeds

insoluble fiber is found

in fruit skin, bran of grains, and some fibrous veggies (celery)

soluble fiber is found

in meat of fruits and beans