The fermentation of dietary fiber by the intestinal flora produces three main end products: short-chain fatty acids, various gases, and energy. Of these, theshort chain fatty acids SCFAs, including acetic, proprionic, and butyric acids, have many important physiological functions. Proprionate and acetate are transported directly to the liver and used for energy production. Proprionate may also help lower an elevated cholesterol level because it is a natural inhibitor of the key enzyme for cholesterol synthesis within the liver (HMG Co A reductase inhibitor).
Butyrate provides an important energy source for the cells that line the colon. In fact, butyrate is the preferred source for energy metabolism in the colon. Butyrate production may also be responsible for the anticancer properties of dietary fiber. Butyrate has been shown to possess impressive anticancer activity and is used in enemas for ulcerative colitis. Certain fibers appear to be more effective than others in increasing the level of SCFAs in the colon. Pectins (both apple and citrus), guar gum, and other legume fibers produce more SCFAs than beet fiber, corn fiber, or oat bran.