Quiz 3 Flashcards
LI is composed of:
cecum, colon, and rectum
Functions of LI
ABSORB water and electrolytes
PRODUCE/ABSORB vitamins
FORM/PROPEL feces toward the rectum for elimination
Muscles of LI
longitudinal muscle- Teniae coli
smooth muscle outside colon
smaller/shorter than the underlying circular muscle and mucosa
causes the underlying layers to form pouches/haustra
Haustral contraction is activated by
presence of chyme and serves to move food slowly to next haustra
how long do contents stay in the LI
12-72 hrs from cecum to anal. canal
LI absorbs electrolytes (____, _____,_____) and _____.
Colonic bacteria produces _____ by fermentation: (______,______, _____). These are then ______ into the blood
Secretions of LI:______ and _____
blood drained from colon reaches liver via _____
Na, Cl, K and water
vitamins: K and B vitamins and SCFA
absorbed
mucus and bicarbonate
hepatic portal vein
_______ cells absorb sodium, choride and water
proximal colon is…..
distal colon is…
Fermentation of fiber occurs where?
proximal mucosal cells
ascending and transvers colon together
descending and sigmoid colon together
proximal colon is where fermentation of fiber occurs
How much water is absorbed in LI?
90-95%
What are the mechanisms for SCFA absorption
- 60% passive diffusion
- Active transport
What is fermentation?
Fermentation of fiber mostly occurs where?
the action of bacteria on prebiotic fiber producing gases and SCFAs
Proximal colon(ascending and transverse colon)
What are the SCFAs and what are their characteristics?
Acetate/ Acectic acid:
-most abundant SCFA
-Produced by bacteria and absorbed by colon cells
-used for energy or sent to muscles, kidneys and brain
-small amount metabolized in liver
Propionate/ Propionic acid:
-made by bacteria, absorbed by colon cells
-supports glucose production and fat metabolism
Butyrate/ Butyric acid:
-Main energy source for colon cells
-anti-inflammatory and anti-cancer benefits, supports immune function
What is stool/feces?
-unabsorbed material, progressively dehydrated
-approx 500 ml- 1 L that enters the colon daily is reduced to 150-200g of defecated material
gastrointestinal cells, digestive juice constituents, fiber, small amounts of unabsorbed fat and bile, and bacteria
-bacteria ~30% of dry stool weight
What exactly is dietary fiber?
The typical nutritional fiber includes?
-indigestible polysaccharides
-cellulose, hemicellulose, pectin, lignin, Beta-glucan, mucilage, fructans, gums, resistant starches
polysaccharides are generally extracted from plants, grains, fruits, vegetables, and edible mushrooms
Why are humans unable to digest cellulose?
What are resistant starches?
-the appropriate enzymes to breakdown the beta acetal linkages are lacking
- fiber that passes through the GI tract undigested and ferments in the LI. Act as prebiotic for bacteria
What are amylase inhibitors?
what diseases can they prevent?
inhibit α‐amylase and α‐glucosidase activities
starch blockers, found on the seeds of plants (ex. cereal grains) and legumes, interfere with digestion of dietary starches and other complex carbohydrates
-slowing digestion
-reducing absorption of glucose
-preventing blood glucose spikes
diabetes, hyperglycemia, hyperlipidemia, obesity
Anatomy of a kernel/cereal
_____ and _____ =fiber rich (contain more fiber than other grains
Dietary fibers are mainly provided by ___, on the plant cell walls- over ___%
The _____ layer of the kernel contains vitamins, minerals, essential fatty acids, and a small amount of fiber
whole grains and cereals: rye and barley
bran layer
95%- Cellulose, hemicellulose, pectin, lesser amount of fructans,
resistant starch, and Beta Glucans
germ layer
Dietary vs Functional fiber
Dietary fiber is non-digestible carbohydrates and lignin that occur naturally in plants
-helps improve bowel movement, prevent constipation by softening and increasing the weight and size of stool
functional fiber is extracted from plants or synthetically made and are non-digestible
-improve blood sugar levels by slowing sugar absorption
-lower LDL by absorbing cholesterol preventing it from entering the blood
Dietary fiber can be split into 2 categories ____ and ___.
Give examples of each and what they reduce risk of
Insoluble fiber- cellulose hemicellulose, ligins
Ex. Whole grains, whole-grain cereals, amaranth, bran, bulgur, couscous, oats, rice, quinoa, sorghum, fruits, vegetables, legumes
Reduces risk of Constipation, diverticulosis, certain cancers, heart disease, obesity
Soluble fiber- Fructans, Pectins, Beta-glucans, Gums, and Psyllium
Ex.Onion, garlic, tomatoes, citrus
fruits, prunes, legumes, oats,
barley, quinoa, teff, sorghum, flax
seed, brussels sprouts, carrots
Reduces risk of :Constipation, heart disease, diabetes mellitus, obesity
Dietary fibers vs Functional fibers
LIST THEM!
Dietary fibers- cellulose, hemicellulose, pectins, lignin, gums, beta-glucans, fructans, resistant starches
Functional fibers- Cellulose, pectin, lignin, gums, beta-glucans, fructans, chitin and chitosan, polydextrose and polyols, psylium, resistant dextrins, resistant starches
Cellulose vs hemi cellulose
Cellulose- linear polymer of glucose units
-water insoluble/non-fermentable
thickening or texture agent
-source-all plant foods
hemicellulose- heterogenous composition
-water soluble and insoluble
-linear or highly branched
-fermentable/non-fermentable
-source- whole grain cereals and bran (greatest quantity)
pectin vs lignin
pectin- galacturonic acid is backbone
water soluble / fermentable
viscous gel forming
used to make jellies
Sources: apples, berries, citrus, legumes, nuts and some vegetables
Lignin- highly branched composed of phenolic units
insoluble/non-fermentable
Structural components of plants making cell wall more rigid
noncarbohydrate component of fiber
sources: whole grains, mature root vegetables, fruits with edible seeds, broccoli
gums vs mucilages vs beta glucans
gums- hydrocolloid
fermentable/soluble (viscous gel-forming)
sources: oats, barley legumes
food additives and thickening agents
Mucilages (psyllium)-
high water binding capacity and form viscous gels
flax and psyllium (laxative)
Beta glucans-
Homopolymer
soluble/fermentable
viscous gel forming
oats and barley
lower LDL
Fructans: include inulin, oligofructose, and fructooligosaccharides
fructose units in chains varying in length
linear or branched
water soluble/fermentable
resistant to hydrolysis and absorption
inulin and oligofructose= dietary fibers
fructooligosaccharides- functional fiber
Prebiotics
sources: chicory, asparagus, leeks, onions, garlic, artichokes, tomatoes, bananas
What are resistant starches and types
specific type of carbohydrate and prebiotic fiber that resists digestion in the small intestine and travels intact all the way to the colon to be fermented by the good bacteria
RS1-resist digestion, inaccessible within plant structure
RS2- semi-crystalline granules present in food , heating releases the starch
RS3- occurs when gelatinized starch is cooked and cooled
RS4-synthetically made to thicken food
RS5-bound to lipids, changing its structure and making it more resistant to digestion
What are oligosaccharides and where are they found?
3-10 sugar units linked by glycosides bonds
Raffinose, stachyose, and verbascose
prebiotic in the body and are fermented by the beneficial to in the gut to promote the health of the gut microbiome
often found in legumes
IBS vs IBD
IBS does not lead to serious disease. Symptoms include abdominal pain, bloating, diarrhea, and other discomforts. Possibly because of problems with how the nerves and muscles in their gut work
IBD: chronic conditions caused by an abnormal response by the immune system, causing inflammation of GI tranct
-Ulcerative colitis- colon
Crohn’s disease- GI tract
How to treat IBS?
Low FODMAP diets
FODMAP: Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols
Three-step elimination diet (4-8 weeks):
1. Stop eating high FODMAP foods
2. Slowly reintroduce them to see which ones are troublesome
3. When foods that cause symptoms are identified
– Avoid/limit while introducing the other foods.
– Foods that trigger symptoms vary from person to person
What are the subcategories within the FODMAPs
Oligosaccharides: fructans, galactans (galactose-galactose bonds that are not absorbed)
Disaccharides: lactose (dairy products)
Monosaccharides: Fructose (fruits, honey, agave, high-fructose corn syrup)
Polyols- sugar alcohols
What dietary fibers are more likely and less likely to be soluble in water?
soluble/insoluble fibers characteristics
Grains and vegetables are more insoluble
Fruits are more soluble
soluble fibers can affect nutrient absorption preventing fats from being absorbed and slow digestion rate of carbohydrates
insoluble fibers increase stool weight and decrease colonic transit time
Viscosity and Gel formation characteristics
Pectins, Beta Glucans, Mucilages (e.g., psyllium), Gums (e.g., guar)
Ability of fiber to bind or hold water (several times their weight )
* Reduced nutrient digestion (interference with enzymes)
* Decreased nutrient diffusion rates
* Decreased absorption of nutrients
* Delayed (slowed) gastric emptying
* Increased gastric distension
* Longer intestinal transit time
* Reduced lipid absorption and enterohepatic recirculation of bile
Roles of fiber on cardiovascular disease
Lower LDL levels
Soluble viscous, gel-forming fibers -bind to and excrete cholesterol
-inhibit the reabsorption of bile acids in intestines prompting the liver to use more cholesterol to produce new bile acids
-interfere with the absorption of cholesterol and bile acids
-fermentation produces SCFAs associated with a reduction in cholesterol synthesis in the liver
Roles of fiber in Diabetes
Diabetes
– Improved glycemic control and insulin sensitivity
* Soluble viscous, gel-forming fiber slow down the digestion and
absorption of carbohydrates; lower post-meal blood glucose
levels.
* Soluble viscous, gel-forming fiber improve insulin sensitivity,
helping cells respond more effectively to insulin
Roles of fiber in appetite and weight control
Lower energy density foods; higher volume → promotes
satiety
- Soluble fibers stimulate the release of GLP-1 → Increased satiety
- Viscous gel forming fibers suppress the release of Ghrelin “hunger hormone” (stimulates appetite) → reduced appetite
- Soluble fibers stimulate the release of PYY (peptide YY) →
Increased Satiety
Roles of fiber in gastrointestinal disorders
Inadequate intake related to diverticular disease, colon cancer and
constipation
* Benefits provided by fiber: Increased fecal output, accelerating intestinal transit,
increasing fecal frequency, and altering bacterial metabolism
