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
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.
Gamma oryzanol is thought to work by impairing cholesterol absorption in the digestive tract.
Additionally, gamma oryzanol has
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
have returned negative results.
Gamma oryzanol is used by some athletes based on early reports that suggested gamma oryzanol enhances muscle growth and
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,
study found that 9 weeks' consumption of gamma oryzanol at a dose of 500 mg daily affected neither anabolic hormone levels nor performance.
Evidence from animal studies suggests that gamma oryzanol may help prevent
, but meaningful human trials are lacking.
Gamma oryzanol has also been advocated as a treatment for
, 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).
This, in turn,
conceivably help menopausal symptoms, but it is a long way from theoretical benefits in rats to proof of effectiveness in humans. One
sometimes touted as direct evidence for benefit in menopause, lacked a control group and therefore means nothing.
(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.
However, the maximum safe dosages for young children, pregnant or nursing women, or those with severe liver or kidney disease have not been established.