Fiber Flashcards
Difference between starch and cellulose?
Cellulose is beta 1,4 linkages whereas starch is alpha
What is hemicellulose? Is it insoluble or soluble?
Branched polymer with a backbone of xylose, mannose, galactose. It is insoluble unless it has an acidic side chain (glucuronic acid). Other side chains are arabinose and galactose
What is Pectin? Is it soluble? What happens to it in the gut?
Pectin is a soluble branched polymer in fruits. It is completely degraded by bacteria. The backbone is galacturonic acid, which is glucose with a carboxyl as C6 instead of alcohol.
What is a trait of insoluble fibers? What are they?
Lignin, Cellulose, Some hemicellulose (unless they have acidic side chain)
What are the soluble fibers?
Non viscous: Fructans and some Hemicelluloses
Viscous: psyllium, Beta glucans, pectins, gums
What are lignin’s? Are they soluble?
They are branches of Phenyl Propane Derivatives and are absolutely not soluble (they fucking hold up trees). They are also in stems and seeds of fruit.
What are gums?
They are soluble (makes sense, plants secrete them). They are common food additives and are completely fermented by gut bacteria.
What are beta glucans?
They are soluble and are in oats, barley and shrooms. They are fermented by gut to short chain fatty acids. Beta glucans are polymers of glucopyranose subunits.
What are fructans?
Soluble fibers. They are polyfructose and found in asparagus, leeks, onions,, garlic, tomato and ‘nanas. They are PREBIOTICS promoting growth of bifidobacteria (gram positive anaerobes in the gut).
What is a good gut bacteria? Why is it good? what is a probiotic?
Bifidobacteria (spina BIFIDa is bad. but BIFIDobacteria is good!). Bifidobacteria make a lot of lactic acid which kilsl other more harmful bacteria. Fructans (polyfructose) is probiotic.
What is psyllium?
Soluble viscous fiber (its metamucil. “metamucil is “Psylli”). Super indigestible and holds a lot of water to increase bulk of what is going through so less accessibility to nutrients. It has a structure similar to gums.
What is polydextrose?
“other fiber” that is synthetic food additive that replaces sugar b/c similar structure to sucrose to hit taste buds, but it is otherwise indigestible
What is the benefit of soluble fibers?
They delay gastric emptying time and time through the GI and decrease uptake. If viscous they really get in the way (psyllium)
What is the benefit of insoluble fibers?
They decrease intestinal transit time and increase fecal bulk.
What is the glycemic index?
It measures how much blood glucose increases after ingestion (high fiber foods have lower glycemic index)
What does fiber do?
Decreased lipid absorption (prevents micelle formation required for uptake)
Lower Cholesterol concentration (increased excretion and reduced uptake of bile acids)
Gut microbiome (promotes growth of lactobacilli and bifidobacteria. They also generate short chain fatty acids)
Increased fecal bulk (decreased intraluminal pressure decreases diverticulitis. WHY metamucil is pushed for many patients in New Ulm)
How does fiber reduce gut inflammation?
They can be broken to short chain fatty acids by bacteria. SCFA can then bind GPR43 on immune cells which decrease immune response which would otherwise be running rampant in the presence of the antigen released by the flora.
Where is GPR43 other than immune cells?
It is on adipocytes and SCFA block the insulin affect on adipocytes so less traicylglyceride is mad because SCFA mediated GPR43 activation suppresses insulin mediated fat accumulation and regulates the energy balance by suppressing accumulation of excess energy and promoting fat consumption.
What does breast milk have that is relevant to this lecture? What is the benefit?
There are indigestible fibers. They have glucose and galactose with beta bonds that we can’t digest. They are metabolized and the oligosaccharides have immunomodulatro effects to promote good bacterias (bifidobacterium) and not bad kinds!
