Digestive processes in the human colon.
Level 5 - mechanism / opinion, no new human data
Narrative review synthesizing physiological mechanisms without primary trial data or systematic review methodology.
What was done
This narrative review synthesized physiological mechanisms of colonic digestion and energy salvage in humans, focusing on the fermentation of starch, nonstarch polysaccharides, and unabsorbed protein into short-chain fatty acids (SCFAs).
What was found
Colonic bacterial fermentation provides 60% to 90% of energy requirements in herbivorous animals, compared to 5% to 10% in humans with intact small-bowel length and function. In patients with upper-gut malabsorption or short bowel syndrome, large amounts of dietary substrates reach the cecum, making colonic fermentation a more important energy salvage mechanism. The degree and rate of colonic starch fermentation depend directly on its susceptibility to small-intestinal amylase hydrolysis.
Why it matters
The findings highlight the capacity of the human large intestine to salvage calories from unabsorbed carbohydrates, which is clinically relevant for managing patients with short bowel syndrome and malabsorptive disorders.
Limits
The abstract describes a narrative review and does not report primary clinical data, sample sizes, or systematic review search criteria. Exact quantitative contributions in specific clinical populations are not reported in the abstract.
Cited by
- supports Short-chain fatty acids produced from fiber fermentation by the gut microbiome can account for around 10% of total dietary energy uptake in some people.