Dietary fibre and cancer

Early epidemiological studies suggested that dietary fibre could be protective against colon cancer. Many isolated fibres were tested for anticarcinogenic activity in carcinogen-treated rats. Wheat bran was consistently protective. Some human studies suggest that dietary wheat bran may protect against growth of colon adenomas. The precise mechanism by which fibre exerts its effects is still elusive. Fibre exerts many influences in the digestive tract. It can dilute the tract contents, and studies show that decreased concentration of faecal bile acids is correlated with reduced cancer risk. Fibre may enhance energy excretion and caloric intake has been correlated positively with cancer risk. Bacterial degradation of fibre produces, among other compounds, butyric acid which may affect colonic and faecal pH and also shows antiproliferative activity. More data are needed vis-à-vis effects of dietary fibre on human colon cancer. These should include studies of specific fibres as well as of high fibre diets. The mechanism(s) of fibre action, including effects on oncogenes, steroid metabolites and short chain fatty acids, requires elucidation.