Medically reviewed on June 7, 2018
What is Gamma Oryzanol?
Rice bran oil is extracted from the bran fraction of rice, the kernels or seeds of the rice plant. It contains large amounts of gamma oryzanol, a mixture of antioxidant compounds. The outer chaff of the rice seed is milled off to produce brown rice; further milling removes the bran portion (the rest of the husk and the germ portions), creating white rice. The rice plant has long, slender leaves, and small wind-pollinated flowers. The species is native to South Asia and some parts of Africa but is cultivated widely. As a cereal grain, it is a major source of nutrition for a large portion of the world's population.
Oryza sativa L.
Gamma oryzanol is also known as rice bran oil, rice bran wax, rice bran protein, gamma oryzanol, and gammariza.
What is it used for?
Rice bran oil is used extensively, especially in Asia, for cooking. It has a nut-like flavor and a high smoke point, making it suitable for deep frying and cooking at high temperatures. Rice bran extracts are used in the cosmetic industry.
Isolation, extraction, and purification of gamma oryzanol were first reported in the mid-1950s. It has been sold in Japan as a medicine since 1962, first to treat anxiety and later in menopause. Gamma oryzanol and rice bran oil therapy have been used to manage elevated cholesterol and triglyceride levels since the late 1980s.
Clinical trial data are often of poor methodology, making it difficult to support suggested clinical applications; however, rice bran oil and its components may have applications in high cholesterol, cancer, and dermatology.
What is the recommended dosage?
Rice bran oil has been used in doses of up to 800 mg daily in clinical studies in high cholesterol. Purified gamma oryzanol has been used at a daily dose of 500 mg/day.
Contraindications have not yet been identified; however, use of products containing phytic acid, a chemical constituent of rice seed, is not advised in patients with poor kidney function.
Information regarding safety and efficacy in pregnancy and lactation is lacking.
None well documented.
Rice bran oil and extracts are considered to be very safe, with only a low incidence of minor allergic reactions reported.
Concerns regarding toxicity are largely due to an incident in the late 1960s in Japan when contaminated rice bran oil affected at least 1,800 people. However, rice bran oil has not been shown to cause mutations, or cancer in short-term animal studies. An increase in bladder cancer has been associated with exposure to the sodium salt of phytic acid, but not the potassium or magnesium salts, and an increase of lung cancer has been suggested for high-dose gamma oryzanol.