Rice bran oil, not fiber, lowers cholesterol in humans
Author: Most, M. M., Tulley, R., Morales, S., Lefevre, M.
Rice bran, a coproduct of milled rice, and its oil may have cardiovascular health benefits. Human consumption of rice bran has been limited, primarily because of the rapid onset of rancidity in rice bran, but methods to stabilize rice bran and to extract its oil have been developed. Interest in rice bran grew from the determination that the inclusion of oat bran in the diet lowers serum cholesterol. Studies of rice bran supplementation in humans found similar beneficial effects on lipoproteins. In a 10-wk controlled feeding trial, rice bran was as effective as oat bran in lowering blood cholesterol concentrations in men and women with moderately high blood cholesterol concentrations.
Rice bran contains 10–23% oil and (unlike oat bran) negligible amounts of water-soluble -glucans and larger amounts of insoluble dietary fiber. Because of these differences, it is believed that rice bran lowers cholesterol by a mechanism different from that of oat bran. Decreases in cholesterol were found in hypercholesterolemic subjects who replaced their usual cooking oils with rice bran oil and in middle-aged and elderly subjects consuming a low-fat diet containing rice bran oil. Yet rice bran oil typically contains 20% saturated fatty acids and approximately equal amounts of oleic and linoleic fatty acids. Previous research showed the deleterious effects of saturated fatty acids on total cholesterol concentrations, and the fact that rice bran oil lowers cholesterol is contrary to these findings. Research now suggests that rice bran oil’s cholesterol-lowering properties are explained by its unsaponifiable components more than by its fatty acid composition. Attention has begun to focus on the components of rice bran oil, including phytosterols, triterpene alcohols, tocopherols, and tocotrienols, as possible hypocholesterolemic agents.
We examined further the cholesterol-lowering abilities of rice bran’s fiber and oil apart from its fatty acid composition. This was accomplished with 2 well-controlled feeding studies designed to evaluate the effects of using defatted rice bran and rice bran oil in an average American diet on cardiovascular disease risk factors in men and women.
Tags: cholesterol, hypercholesterolemic, rice bran, rice oil, unsaponifiable