Gamma-oryzanol is one of several lipid fractions obtained from rice bran oil.
Gamma-oryzanol is a mixture of phytosterols (plant sterols), including campesterol, cycloartanol, cycloartenol, beta-sitosterol, stigmasterol, and also ferulic acid.
Phytosterols appear to reduce lipid levels and ferulic acid has antioxidant properties. Gamma-oryzanol has also been suggested to have anabolic properties, but evidence is conflicting.
Gamma-oryzanol has been investigated for a role in lipid lowering and improving exercise performance.
Several animal studies1–3 have shown a lipid-lowering effect with gamma-oryzanol supple-mentation, but one study did not.4
In two uncontrolled studies in humans with hyperlipidaemia, gamma-oryzanol was shown to reduce serum cholesterol levels. One study involved 80 patients with hyperlipidaemia who were given gamma-oryzanol for 6 months. In those with type IIa and IIb hypercholesterol-aemia, serum cholesterol fell by 12% and 13% respectively, but the reduction was significant only after 3 months. Plasma triglycerides reduced significantly after 3 months and there was a non-significant increase in HDL cholesterol.5
In the other study, 20 patients with chronic schizophrenia with dyslipidaemia were given 300 mg gamma-oryzanol daily for 16 weeks. Both total and LDL cholesterol fell significantly, but there was no significant change in HDL levels.6
In a double-blind, placebo-controlled study, 22 weight-trained men were given 500 mg gamma-oryzanol daily or placebo for 9 weeks. There were no differences between the groups for measures of circulating concentrations of testos-terone, cortisol, oestradiol, growth hormone, insulin or beta-endorphin, blood lipids, cal-cium, magnesium and albumin. Resting cardiovascular variables decreased in both groups and vertical jump power and one-repetition maximum muscle strength (bench press and squat) increased in both groups. The authors concluded that gamma-oryzanol 500 mg for 9 weeks did not influence either performance or physiological parameters in moderately weight-trained men.7
None have been reported.
Pregnancy and breast-feeding
No problems have been reported, but there have not been sufficient studies to guarantee the safety of gamma-oryzanol in pregnancy and breast-feeding.
There are no long-term studies assessing the safety of gamma-oryzanol in humans. There is some evidence from a Japanese study that doses up to 600 mg daily cause dry mouth, somnolence, hot flushes, irritability and headaches.8
Gamma-oryzanol is available in the form of tablets and capsules.
The dose is not established. Dietary supplements provide 100–500 mg daily.
Preliminary evidence from animal studies and uncontrolled studies indicates that gamma-oryzanol may reduce serum cholesterol levels. There is no good evidence that it improves exercise performance. Further research is required.
Seetharamaiah GS, Chandrasekhara N. Studies on hypercholesterolemic activity of rice bran oil. Atherosclerosis 1989; 78: 219–223.
Rukmini C, Raghuram TC. Nutritional and bio-chemical aspects of the hypolipidemic action of rice bran oil: a review. J Am Coll Nutr 1991; 10: 593–601.
Rong N, Ausman LM, Nicolosi RJ. Oryzanol decreases cholesterol absorption and fatty streaks in hamsters. Lipids 1997; 32: 303–309.
Sugano M, Tsuji E. Rice bran oil and cholesterol metabolism. J Nutr 1997; 127: S521S–S524.
Yoshino G, Kazumi T, Amano M, et al. Effects of gamma-oryzanol and probucol on hyperlipidemia, Curr Ther Res 1989; 45: 975–982.
Sasaki J, Takada Y, Handa K, et al. Effects of gamma-oryzanol on serum lipids and apolipopro-teins in dyslipidemic schizophrenics receiving major tranquillisers. Clin Ther 1990; 12: 263–268.
Fry AC, Bonner E, Lewis DL, et al. The effects of gamma-oryzanol supplementation during resistance exercise training. Int J Sport Nutr 1997; 7: 318–329.
Takemoto T. Clinical trial of Hi-Z fine granules (gamma-oryzanol) on gastrointestinal symptoms at 375 hospitals. Shinyaku To Rinsho 1977; 26 (in Japanese).