The effect of dietary fiber on colonic cell proliferation and serum and tissue cholesterol levels

Abstract

High serum cholesterol is a significant risk factor for coronary heart disease. Dietary fibers may lower serum cholesterol levels thus reducing the risk for heart disease. Some dietary fibers are known to increase cell proliferation in the colon resulting in the potential for increased susceptibility to carcinogens. Is it possible to consume the fiber necessary to keep serum cholesterol levels at safe levels without putting the colon at risk? In this study we show that it is possible to consume a mixed fiber diet that has the desired effect on serum cholesterol levels while not significantly altering colonic physiology. Compared to fiber-free, cellulose, oat bran and pectin fed animals the mixed fiber diet had effects on serum cholesterol similar to those seen in the pectin and oat bran fed animals. The mixed fiber diet did not have the effects on colonic cell proliferation typical of in the pectin and oat bran diets. Pectin had significantly more of a lipid lowering effect on liver than did the other fibers while lowering serum cholesterol significantly more than cellulose or oat bran. Comparisons were also made among the fiber diets and two forms of rat chow (powdered and pelleted). Since the defined diets were designed to increase serum cholesterol, many differences were seen between defined diet fed animals and rat chow fed animals. Significant differences were also seen between measurements in the powdered and pelleted chow fed rats.