Gamma oryzanol is a mixture of substances derived from rice bran oil, including sterols and ferulic acid. It has been approved in Japan for several conditions, including menopausal symptoms, mild anxiety, stomach upset, and high cholesterol. In the US, it is widely used as a sports supplement, as well as for reducing cholesterol. However, there is no meaningful evidence supporting the use of gamma oryzanol for any of these purposes.
There is no daily requirement for gamma oryzanol.
Rice bran oil is the principal source of gamma oryzanol, but it is also found in the bran of wheat and other grains, as well as various fruits, vegetables, and herbs. However, to get enough gamma oryzanol to reach typical therapeutic dosages, you will need to take supplements.
Like many other vegetable oils, rice bran oil appears to improve cholesterol profile . 8 Preliminary evidence, including small double-blind, placebo-controlled trials , suggests that the gamma oryzanol portion of rice bran oil may contribute an additional cholesterol-lowering benefit beyond the effects of the fatty acids. 2,3,8,10 Gamma oryzanol is thought to work by impairing cholesterol absorption in the digestive tract. 11
Additionally, gamma oryzanol has antioxidant properties. It has been hypothesized that antioxidants can help protect against heart disease, cancer, and other illnesses; however, it must be kept in mind that gigantic studies looking for such benefits with the antioxidants vitamin E and beta-carotene have returned negative results. 8
Gamma oryzanol is used by some athletes based on early reports that suggested gamma oryzanol enhances muscle growth and sports performance . 5,6,9 According to numerous websites, gamma oryzanol produces these benefits by increasing levels of testosterone, growth hormone, and other anabolic (muscle-building) hormones. However, there is no real evidence that gamma oryzanol either affects these hormones or enhances performance, and some evidence that it does not. For example, double-blind, placebo-controlled study found that 9 weeks' consumption of gamma oryzanol at a dose of 500 mg daily affected neither anabolic hormone levels nor performance. 7
Gamma oryzanol has also been advocated as a treatment for menopausal symptoms , but the basis of this potential use consists of evidence far too weak to be relied upon at all. In one study, gamma oryzanol injected into rats altered levels of circulation luteinizing hormone (LH). 8 This, in turn, might conceivably help menopausal symptoms, but it is a long way from theoretical benefits in rats to proof of effectiveness in humans. One open study , sometimes touted as direct evidence for benefit in menopause, lacked a control group and therefore means nothing. 1 (For information on why this is so, see Why Does This Database Rely on Double-blind Studies? )
In the late 1970s, a batch of rice bran oil was contaminated by PCBs (polychlorobiphenyls), resulting in the poisoning of more than 2,000 people. This led to studies on the safety of gamma oryzanol products. On balance, the results of these investigations suggest that gamma oryzanol, when taken at normal doses, is nontoxic and noncarcinogenic. 8 However, the maximum safe dosages for young children, pregnant or nursing women, or those with severe liver or kidney disease have not been established.
11. Berger A, Rein D, Schafer A, et al. Similar cholesterol-lowering properties of rice bran oil, with varied gamma-oryzanol, in mildly hypercholesterolemic men. Eur J Nutr . 2004 May 19. [Epub ahead of print]
Last reviewed September 2014 by EBSCO CAM Review Board
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