Dietary Intake of Dietary Fiber and Cancer

Many studies have been reported that dietary wheat bran, cellulose, resistant starch and inulin suppressed experimental colon tumors or cancer in rats. Dietary fiber reduces contact between the intestinal contents and mucosa, and leads to production of short-chain fatty acids, acetate, propionate, and butyrate, which reduce pH and the conversion of primary to secondary bile acids. Butyrate is the major source of energy for the distal colon and it reduces cell proliferation and induces apoptosis, factors that are associated with inhibition of the transformation of the colonic epithelium to carcinoma. On the other hand, dietary fiber is thought to protect against colorectal cancer in human but this view has been challenged by recent cohort studies that showed no protective effect.