Effects of short chain fatty acids on gut morphology and function.

Short chain fatty acids (SCFAs) are the products of colonic bacterial degradation of unabsorbed starch and non-starch polysaccharide (fibre). They are important anions in the colonic lumen, affecting both colonocyte morphology and function. The three main acids (acetate, propionate, and butyrate) stimulate colonic sodium and fluid absorption and exert proliferative effects on the colonocyte. Experimental animal studies have shown that they promote adaptive responses to small intestinal resection and colonic anastomosis. Acetate increases colonic blood flow and enhances ileal motility. Butyrate has been shown to be the preferred energy substrate for the colonocyte and to be a potent differentiating agent in cell culture. Butyrate may also have a role in preventing certain types of colitis. A diet low in resistant starch and fibre, which will result in a low production of SCFAs in the colon, may explain the high occurrence of colonic disorders seen in the Western civilization.