This fermentation product of dietary fibre is known to be present in the colonic lumen in the millimolar range and levels can be modulated by intake of suitable dietary substrate [ 10].
These include xylo-oligosaccharides (XOS), galacto-oligosaccharides (GOS) and fructans, including inulin and fructo-oligosaccharides (FOS ., Any dietary substrate that remains undigested in the upper GIT, and that may have beneficial effects, is however a potential prebiotic.
By degrading dietary substrates, the gut microbiota produces several metabolites that bind human pharmacological targets, impact subsequent signalling networks and in fine modulate host's metabolism.
Replacement of lactose by other dietary substrates can be economically attractive, and may also positively (or negatively) affect the risk of developing problems with glucose metabolism.
Similarly, a previous research detected that the microbial fermentation and absorption of indigestible dietary substrates primarily occur in the rumen and colon and not in the small intestine (Abbeele et al. 2011).
The gut types were also detected in fecal samples from a range of other mammalian species, with the highest levels in herbivores, consistent with a role in fermentation of dietary substrates.
The composition and interactions of the gut microbiota may affect the amount of energy extracted from the diet and energy harvest [ 4, 5], and play an important role in the metabolism of dietary substrates and immune system modulation [ 6].
Issues associated with age, phenotypic plasticity, antecedent food availability (i.e., periods of starvation) as well as the relative levels of different dietary substrates have emerged from both field and controlled laboratory studies as possibly inducing changes in intestinal length [ 17, 33, 79, 80].
Carbohydrate is the main energy source for prolonged physical activity [4], and of the dietary energy substrates, carbohydrates are most readily digested and absorbed.
The CYPs comprise a superfamily of haemoproteins that catalyse the initial monooxygenation of a range of lipophilic endogenous, environmental or dietary xenobiotic substrates (Guengerich, 1992; Crofts et al, 1998).
Studies in rats treated with a colorectal carcinogen, have demonstrated a variable protective effect of different dietary fibre substrates and have linked this with changes in the luminal SCFA profile [ 7].
