Primary prevention of colorectal cancer through dietary modification.

Because colorectal cancer is the second leading cause of cancer death in the United States and many developed countries, its primary prevention is of extreme importance. Environmental and dietary factors are considered responsible for 85-90% of all cases. Epidemiologic, animal, and biochemical studies suggest that diets high in total calories and fat and low in various dietary fibers, vegetables, and micronutrients are associated with an increased incidence. Of these factors, calcium and wheat bran have been used most extensively in recent trials. It has been reported that 1.5-2.0 g/day of calcium significantly decreases DNA synthesizing cells of high-risk patients. However, chronic wheat bran supplementation appears to decrease both rectal mucosal DNA synthesis and polyp recurrence. Several clinical trials currently are underway to evaluate the diet-colon cancer link. The results of these studies will help to determine the importance of dietary intervention in the reduction of the colorectal cancer risk.