The bacterial flora helps the fermentation of undigested substrates and endogenous mucins, the energy recovery by releasing short-chain fatty acids (SCFA), protects against invasion of pathogens, and leads the development, stimulation and modulation immune system.
We have some foods that go directly to give us these live microorganisms, which are taken in order to obtain a beneficial effect independent of their intrinsic nutritional value (eg, prevention and treatment of infectious diarrhea, lactose intolerance or modulation of the system immunity from allergies).
Their physiological effects are largely derived from its fermentation colonic motility by acting on the intestinal flora and the absorption and metabolism of nutrients with exceptional and unique qualities of the colonocyte. The short-chain fatty acids (acetic, propionic and butyric acids, SCFA) may induce growth and healing of colonic mucosa and butyrate is the main energy substrate of the same.
The most important effects of the SCFA, are partly decrease intraluminal pH, stimulate water and sodium reabsorption mainly
in the ascending colon, and enhance absorption in the colon of divalent cations.
In general, soluble fiber slows the rate of transit time in the stomach and small intestine, is rapidly fermented by bacteria in the colon and has a laxative effect. The fibers are predominantly insoluble type laxative effect and are not fermented or are only sparingly.
Viscous fibers reduce absorption rates, decreasing blood concentrations of some nutrients such as glucose or cholesterol.
Arguably, each type of substance has different properties depending on its water solubility, viscosity, ability to ferment or the possibility of inducing systemic effects.