Rice Bran

Scientific Name(s): Oryza sativa L.
Common Name(s): Rice bran oil, Rice bran protein, Rice bran wax

Medically reviewed by Drugs.com. Last updated on Apr 22, 2024.

Clinical Overview

Use

Rice bran oil is used extensively in Asia for cooking because of its high smoke point. Potential benefit with use of rice bran oil and its components (particularly gamma oryzanol) for dermatological applications and dyslipidemia has been suggested; however, due to the possible severity of dyslipidemia, rice bran variations should not be used in lieu of standard medical care. Clinical trial data are limited by poor methodology and quality, making it difficult to support suggested clinical applications.

Dosing

Hypercholesterolemia: A dosage of 50 mg/day of a tocotrienol-rich fraction of rice bran (either alone or in combination with lovastatin) was administered for 35 days as part of a 5-phase study over 25 weeks. In another study of hypercholesterolemic men, gamma oryzanol was administered at a low dose (50 mg/day) or high dose (800 mg/day) for 4 weeks. Exercise performance: Gamma oryzanol 500 to 600 mg/day for 9 weeks has been evaluated for its effects on exercise training and muscle strength.

Contraindications

Contraindications have not been identified; however, use of the component phytic acid in renal impairment is not advised.

Pregnancy/Lactation

Information regarding safety and efficacy in pregnancy and lactation is lacking.

Interactions

None well documented.

Adverse Reactions

Rice bran oil and extracts are considered very safe, with only a low incidence of minor allergic reactions reported.

Toxicology

No data.

Scientific Family

• Poaceae (grass)

Source

The rice plant grows up to 1.8 m in height, depending on location and conditions. It has long, slender leaves and small wind-pollinated flowers. The species is native to South Asia and some parts of Africa but is widely cultivated. As a cereal grain, it is a major source of nutrition for a large portion of the world's population.Murray 1996, USDA 2017

The outer chaff of the rice seeds are milled off to produce brown rice, which is covered by bran layers; rice bran oil is extracted from the bran fraction of rice kernels or seeds of the rice plant. Gamma oryzanol, as well as other constituents, are extracted from rice bran oil.Park 2017

Related/similar drugs

acetylcysteine, ascorbic acid, biotin, Vitamin C, multivitamin, Dextrose

History

Rice bran oil is used extensively in cooking, especially in Asia. 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 used 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.Murray 1996, Safety Assessment 2006

Chemistry

Rice bran oil, gamma oryzanol, ferulic acid, and phytic acid are chemical constituents of rice seed.

The bran fraction is approximately 8% of the rice kernel and consists of saturated and unsaturated fatty acids and alcohols, phytosterols, tocotrienols, tocopherols, vitamins (including biotin, vitamin B₁₂, thiamine, and niacin), and minerals (including phosphorous, magnesium, potassium, and zinc).

Gamma oryzanol is a mixture of esters of sterols (eg, campestrol, stigmasterol, beta-sitosterol) and triterpene alcohols and their ferulate esters. Approximately 7,500 tons of gamma oryzanol are processed from rice bran in Japan each year. Hydrolyzed rice bran protein containing a high portion of globulins and albumins is also extracted from the bran.Murray 1996, Park 2017, Safety Assessment 2006, Sato 1981

Uses and Pharmacology

Cancer

Animal and in vitro data

Rice bran oil and its constituents have been investigated in animal studies, as well as in vitro using various human cancer cell lines. Reviews of the literature have been published. Most studies report antineoplastic action; however, not all evidence is unequivocal.Fox 2002, Szczesniak 2016, Tan 2017

Dermatologic effects

Animal and in vitro data

Gamma oryzanol applied topically to rats increased sebaceous secretion and turnover of sebaceous gland cells. Increases in peripheral blood flow were also observed.Yasukawa 1998 The ferulates in gamma oryzanol may adsorb ultraviolet radiation.Viriyaroj 2009 Squalene extracted from rice bran oil has been shown to exert emollient, hydrating, and antioxidant properties in skin models and has been used as a vehicle in lipid emulsions.Huang 2009

Clinical data

Based on animal experiments, proposed applications for gamma oryzanol include antiaging effects and the repair of damaged or dry skin.Viriyaroj 2009, Yasukawa 1998 Gel and cream formulations containing semipurified rice bran extracts (ferulic acid, gamma oryzanol, and phytic acid) have been tested on the skin of 30 human volunteers in an open-label study. The formulations demonstrated anti-aging activity (ie, hydration enhancement and improvement of skin lightening, thickness, roughness, and elasticity).Manosroi 2012 Randomized clinical trials are lacking.

Dyslipidemia

Animal data

Most animal studies evaluating gamma oryzanol and its related constituents (eg, tocotrienols, beta-sitosterol) have demonstrated hypocholesterolemic effects, possibly due to the widely acknowledged ability of plant sterols to inhibit cholesterol absorption from the intestine. The availability of existing data from animal experiments and the relative safety of rice bran oil make data from further animal experiments largely redundant. Reviews of the literature have been published.Park 2017, Szczesniak 2016

Clinical data

Clinical studies are promising; however, the methodology of many trials is poor.Fry 1997, Kerckhoffs 2002, Sen 2007 Reduced total cholesterol and triglyceride levels and increases in the high-density lipoprotein:low-density lipoprotein ratio have been demonstrated in clinical studies of rice bran oil and its constituents. Mechanisms may include stimulation of cholesterol catabolism and suppression of hydroxymethylglutaryl coenzyme A reductase, as well as inhibition of cholesterol absorption from the intestines.Accinni 2006, Berger 2005, Most 2005, Park 2017, Utarwuthipong 2009, Vissers 2000 Action on pancreatic islets and enhanced insulin secretion have also been reported for gamma oryzanol, suggesting a possible role in type 2 diabetes management.Kozuka 2013

Exercise training performance

Animal data

Endocrinological studies in animals indicate that gamma oryzanol suppresses luteinizing hormone release and reduces growth hormone.Cicero 2001 Gamma oryzanol may reduce testosterone production.Wheeler 1991

Clinical data

Few well-controlled clinical trials exist, with most evidence coming from studies of adequate methodology that suggest no influence of rice bran oil or gamma oryzanol on performance during resistance exercise training.Cicero 2001, Fry 1997, Manore 2011, Szczesniak 2016 One small study (N=30) found no effect on anthropometric and body measurements with gamma oryzanol 600 mg/day supplementation over 9 weeks, but did report an increase in muscular strength.Eslami 2014 Two other clinical trials reported increased postexercise beta-endorphin levels and increased body weight and muscular strength with ferulate supplementation.Manore 2011

Other uses

Gamma oryzanol has been evaluated for its neuroprotective properties, with antioxidant, immunomodulatory, and anti-ulcerogenic effects, among others, reported.Sen 2007, Szczesniak 2016

Dosing

Some studies suggest that gamma oryzanol is poorly absorbed, with the bulk of the dose excreted in the feces, but that the ferulic acid component is well absorbed.Grunewald 1993, Manore 2011

Hypercholesterolemia

A dosage of 50 mg/day of a tocotrienol-rich fraction of rice bran (either alone or in combination with lovastatin) was administered for 35 days as part of a 5-phase study over 25 weeks.Sen 2007 In another study of hypercholesterolemic men, gamma oryzanol was administered at a low dose (50 mg/day) or high dose (800 mg/day) for 4 weeks.Berger 2005

Exercise training performance

Gamma oryzanol 500 to 600 mg/day for 9 weeks has been evaluated for its effects on exercise training and muscle strength.Eslami 2014, Fry 1997

Pregnancy / Lactation

Information regarding safety and efficacy in pregnancy and lactation is lacking. Avoid doses higher than usual dietary amounts.

Interactions

None well documented. A study evaluating the effect of gamma oryzanol on cytochrome P450 (CYP-450) reactions showed little inhibition of CYP activity. Therefore, interactions dependent on these pathways are unlikely.Umehara 2004 Chelation of certain elements has been demonstrated for phytic acid in animal studies, and iron absorption with concurrent rice bran product intake has been studied, but case reports for such interactions are lacking.Fox 2002

Adverse Reactions

Rice bran oil and extracts are considered very safe, with only a low incidence of minor allergic reactions reported despite the common understanding that rice is hypoallergenic. Case reports of urticaria from raw rice exist. Lotions containing rice bran oil show a low incidence of minor skin irritation.Safety Assessment 2006 In experimental animal studies of phytic acid, renal papillae changes have been observed, including necrosis and calcification. Therefore, use in renal impairment is not advised.Fox 2002

No adverse effects have been reported with use of gamma oryzanol in animal or clinical studies.Murray 1996

Toxicology

Short-term toxicity studies in rodents suggest the median lethal dose (LD₅₀) of rice bran oil is 25 g/kg. Gamma oryzanol has not been shown to be mutagenic or clastogenic in models and is not carcinogenic in mice or rats. No gross abnormalities have been found upon necropsy in short-term studies. In an animal study evaluating the toxicological effect of rice bran oil on reproduction performance, no abnormalities were reported over 2 matings and 3 generations.Szczesniak 2016

An increase in bladder cancer has been associated with the sodium salt of phytic acid, but not the potassium or magnesium salts, and an increase of lung cancer has been suggested with high-dose gamma oryzanol.Fox 2002, Hirose 1991

Concern regarding toxicity can be largely attributed to an incident in the late 1960s in Japan when contaminated rice bran oil affected at least 1,800 people. Rice bran oil was contaminated with polychlorinated biphenyls (a dioxin) as well as polychlorinated quaterphenyls and dibenzofurans that resulted from the heating process. The subsequent "Yusho syndrome" has been described, with skin, eyes, and teeth effects, and intractable headache, hyperglyceridemia, and pulmonary symptoms persisting for up to 30 years. It has also been suggested that those in this affected population had a higher risk of developing type 2 diabetes.Imamura 2007, Kanagawa 2008, Wang 2008

Index Terms

• Gamma oryzanol
• Gammariza

References

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