Rice Bran

1. Rice Bran Pennington Biomedical Research CenterDivision of EducationHeli J. Roy PhDShanna Lundy, BSPhillip Brantley, PhD, Director

2. Rice Bran Contents • Rice bran is composed of the aleurone layer of the rice kernel and some part of the endosperm and germ, which are rich sources of proteins, lipids, vitamins, and trace minerals • Rice bran’s oil and unsaponifiable lipid content is high compared with other grains • Unrefined rice bran oil consists of ~20% saturated, 40% monounsaturated, and 40% polyunsaturated fatty acids and contains tocotrienols, γ-oryzanol, and β-sitosterol PBRC 2005

3. Rice bran and its oil contain large concentrations of several compounds that could potentially prevent chronic diseases such as coronary heart disease and cancer • The LSU AgCenter has been actively identifying, extracting, purifying, and evaluating the functionality of several of these compounds PBRC 2005

4. Their initial studies with rice bran focused on stabilizing against lipid degradation that leads to flavor problems • During these studies, it was noted that rice bran contained high levels of both tocopherols and tocotrienols, which compromise vitamin E and act as antioxidants in the body • Also, high levels of a mixture of compounds referred to collectively as oryzanol were identified within rice bran PBRC 2005

5. Oryzanol components are complex compounds that can act as an antioxidant, improving solubility in cell membranes and potentially lowering cholesterol by competitive inhibition of absorption and synthesis • Methods of separating the individual components of the oryzanol mixture have come about, leading to the identification of 3 major fractions of oryzanol: • Cycloartenyl ferulate • 24-methylene cycloartanyl ferulate • Campesteryl ferulate PBRC 2005

6. Because the causes associated with almost all chronic disease can be traced to the effects of oxidants, both in the environment and in our bodies, interest arose in the area of rice bran and its antioxidant capacity • Specifically, cholesterol oxidation products have been suggested as a major cause of heart disease PBRC 2005

7. Rice bran components do reduce cholesterol oxidation • The antioxidant activities of four of the vitamin E and three oryzanol components purified from rice bran were investigated in a chemical model of cholesterol oxidation • All components exhibited significant antioxidant capacity in the inhibition of cholesterol oxidation! • All three oryzanol components were higher than any of the four vitamin E components Found that : PBRC 2005

8. Rice bran & Osteoporosis • Osteoporosis affects more than 20 million older Americans, with the number increasing every year • Because of the risk for cancer associated with hormone replacement therapy in women, alternative methods to reduce bone loss are currently being investigated • Studies on rice bran and its role in osteoporosis have been conducted PBRC 2005

9. Ovariectomized rats (who typically lose substantial bone mineral density after the ovariectomy) were used as a model for postmenopausal osteoporosis • Found that with the addition of a 7% oryzanol rice bran oil (RBO) concentrate to the diets of these rats that reductions in bone loss at several bone sites occurred • The beneficial effect of the RBO concentrate appeared to be primarily on cortical bone in the long bones, and not on the trabecular bone in vertebrae PBRC 2005

10. Crystalline oryzanol and crystalline oryzanol dissolved in corn oil had no effect on bone mineral density • Suggesting that either the oryzanol as it occurs naturally in rice bran oil is more biologically active than crystalline oryzanol or that something else in the rice bran oil is affecting bone density positively PBRC 2005

11. More studies are needed to identify the active elements in rice bran oil beneficial in reducing bone loss and in determining their mode of action • Rice bran oil concentrate appears to primarily act on preserving the slow turn-over cortical bone in the long bones • Other functional foods, such as soy protein, act on rapid turnover trabecular bone in vertebrae • The possibility of using the two together in combination is an area currently under investigation PBRC 2005

12. More on Rice Bran… • In the past, 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 oils have been developed • Interest in rice bran grew from the determination that the inclusion of oat bran in the diet lowers serum cholesterol • Rice bran contains less total dietary fiber and less soluble fiber than oat bran PBRC 2005

13. Studies of Rice Bran .. • Based on its soluble fiber content alone, rice bran should have less hypolipidemic effects than other sources of fiber • However, studies of rice bran supplementation in humans found similar beneficial effects on lipoproteins • In a 10-week controlled feeding trial, rice bran was as effective as oat in lowering blood cholesterol concentrations in men and women with moderately high blood cholesterol concentrations • Has shown reductions in cholesterol levels in pigs, hamsters, rats, humans, and nonhuman primates PBRC 2005

14. What exact component found in rice bran is responsible for its cholesterol-lowering effects? • Possible suggestions have included: • The fiber that is present • The Fatty acid composition • Or the Unsaponifiables present • Oryzanol, phytosterols (campesterol and β-sitosterol) PBRC 2005

15. Evidence from 2 well-controlled studies at Pennington Biomedical Research Center confirms that it is the rice bran oil (RBO), and not the fiber, that lowers blood lipids in men and women with borderline high total cholesterol • Although RBO does contain about 20% saturated fatty acids and approximately equal amounts of oleic and linoleic fatty acids, its’ cholesterol lowering ability is due to its unsaponifiable components more so than by its fatty acid composition PBRC 2005

16. In a recent study, by matching the fatty acids of the rice bran oil with a control oil blend, it was shown that the effect of RBO on serum cholesterol concentrations is due to the unsaponifiables present in it and not to its fatty acid profile • It is believed that RBO containing these compounds could become an important functional food with cardiovascular health benefits PBRC 2005

17. References • http://www.agctr.lsu.edu/Communications/LouisianaAgriculture/agmag/45_4_articles/ricebran.asp • http://www.nutrition.org/cgi/content/full/128/5/865 • http://www.ajcn.org/cgi/content/full/81/1/64 PBRC 2005