number of nutrients have been researched for their ability to lower plasma cholesterol concentrations in humans. In many cases the lowering effects are as great or greater than the current cholesterol lowering drugs of choice, the statins. However, the nutrients show few if any side effects and this makes them superior in a clinical or real world setting when compared to the best the pharmaceutical industry has to offer. A number of vegetable oils rich in linoleic acid (LA, C18:2 (n-6)) are know to be able to lower plasma cholesterol levels in humans, with a number of compounds being identified as possible causative agents. That polyunsaturated fatty acids in vegetable oils are effective at lowering plasma cholesterol levels in humans has been exploited by a number of researchers to create biased research data suggesting that saturated fat is able to cause elevations in plasma cholesterol (here).
Rice bran oil (RBO) may be effective at lowering plasma cholesterol levels because it contains γ-oryzonol and tocotrienols1. In studies, RBO is more effective than other vegetable oils at lowering plasma cholesterol in humans. In particular, mixing RBO with safflower oil in a ratio of 7 to 3 increases the efficacy of the cholesterol lowering effect significantly, when compared to each oil in isolation. The mechanism by which this occurs is not fully understood but may relate to the γ-linolenic acid (GLA, C18:3 (n-6)) content of the safflower oil working synergistically with the tocotrienol and γ-oryzonol of the RBO. Rice bran oil also contains both campesterol and β-sitosterol, both of which have been shown to affect the absorption of cholesterol in humans. Sterol therapy has become a mainstream treatment, suggesting that these components are responsible for some of the cholesterol lowering effects of RBO.
Tocotrienols are of particular interest in cholesterol lowering researcher because they are known β-hydroxy-β-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors2. Statins are thought to lower cholesterol by the same mechanisms, but tocotrienols do not show side effects, making them a superior choice. Rice bran oil contains mainly β-tocotrienol and γ-tocotrienol in higher concentrations than the tocopherols, which is unusual for a vegetable oil. Tocotrienols show a dose dependent effect on cholesterol levels. At 100 mg per day a tocotrienol rich extract of RBO was shown to cause a decrease in total cholesterol, low density lipoprotein (LDL) cholesterol, apolipoprotein B and triglycerides by 20, 25, 14 and 12 %, respectively. Rice bran oil also contains the essential fatty acid α-linolenic acid (ALA, C18:3 (n-3)) which may increase plasma levels of longer chain unsaturated fatty acids, and this may cause decreases in fasting triglyceride levels.
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