Fiber, lipids, and atherosclerosis.

The influence of dietary fiber on lipid metabolism and atherosclerosis in animals and on lipid metabolism in man is reviewed. Pectin, guar gum, and lignin lower serum and liver cholesterol in cholesterol-fed rats. Agar increases liver cholesterol in rats. Bran has no effect on serum lipid levels in rats or monkeys. Vegetarians have long been known to exhibit cholesterol levels lower than those of comparable populations who subsist on a mixed diet. Pectin and guar gum lower cholesterol levels in man whereas cellulose and bran have no effect. Rabbits fed a semipurified diet containing saturated fat become atherosclerotic, but addition of the same fat to laboratory ration has no effect; it has been shown that the residue in laboratory ration is the cause of the difference. Semipurified diets containing cellulose are more atherogenic than those containing wheat straw or alfalfa. The semipurified diets also cause aortic sudanophilia or atherosclerosis in baboons and vervet monkeys. One possible mechanism of hypolipemic action of fiber involves the binding of bile acids, which would result in reduced absorption of cholesterol, resulting in lower levels of serum cholesterol.