colonic fermentation

The breakdown of dietary fibre, resistant starch, and some other undigested foods by bacteria in the large intestine. The end products of fermentation include volatile fatty acids that may contribute up to 10 per cent of human energy requirements. One of the volatile fatty acids, propionic acid, is thought to lower blood cholesterol levels. Another, butyric acid, may have an anti-cancer effect by stimulating the growth of normal cells in the bowel wall rather than cancer cells. A less desirable result of colonic fermentation is that the bacteria cause flatulence containing gases that may include methane. See also gut bacteria.