Benefits
LDL and total cholesterol levels
A pooled analysis of 11 randomized trials (572 people) found rice bran lowered LDL by about 15 mg/dL, with larger effects for rice bran oil than for whole bran. A separate pooled analysis of 8 trials of rice bran supplementation found no significant change in any blood fat. The clearest results come from trials using 30 to 50 g of rice bran oil a day in place of other dietary fats, not a capsule.
Blood sugar response after meals
In a crossover trial in 19 healthy men run by a company research team, adding 16.5 mg of rice bran triterpenoids to a rice meal lowered the rise in blood sugar over 1 to 3 hours, though the overall glucose curve only trended lower. In 28 adults with type 2 diabetes, 20 g a day of stabilized rice bran for 12 weeks lowered after-meal glucose versus their own baseline, not versus placebo.
Sleep onset and sleep efficiency
In a 2-week randomized, placebo-controlled trial in 50 adults with disturbed sleep, 1 g a day of an ethanol rice bran extract standardized to gamma-oryzanol shortened the time to fall asleep and raised total sleep time and sleep efficiency on overnight sleep recordings. Self-rated sleep quality did not differ from placebo. This is a single small trial of one extract, which the maker supplied.
Mood scores in adults with low mood
In an 8-week randomized, placebo-controlled trial in 100 adults with mild to moderate depressive symptoms, 1 g a day of a rice bran extract lowered clinician-rated depression scores more than placebo. Most self-rated scales and blood markers did not differ between groups. This is a single trial of one extract, which the maker supplied; anyone with persistent low mood should talk to a doctor.
Strength gains during resistance training
Gamma-oryzanol has long been sold to lifters. Over 9 weeks of training, weight-trained men taking 500 mg a day gained no more strength or power than those on placebo, and testosterone, cortisol and growth hormone did not differ. A second 9-week trial in 30 young men taking 600 mg a day reported larger bench press and leg curl gains than placebo. The two trials conflict, and the positive one was small.
Menopausal symptom scores
The menopause evidence is decades old. In an early Japanese study, 40 women with menopausal complaints took 300 mg a day of gamma-oryzanol for 4 to 8 weeks, and most improved on standard symptom scores. There was no placebo group, so a placebo response cannot be ruled out.
Mechanism of action
Compounds in the oil fraction and cholesterol uptake
In a controlled feeding study, rice bran oil lowered cholesterol while defatted rice bran fiber did not, pointing to compounds in the oil rather than its fats or fiber. Plant sterols in the oil are thought to compete with cholesterol for absorption, but in one trial oils with low and high gamma-oryzanol lowered cholesterol about equally, so the oryzanol content itself may matter less.
Slower sugar uptake from the gut
In rat gut tissue and human gut-cell experiments, cycloartenol, a triterpene alcohol from rice bran, reduced glucose transport, apparently by limiting how much of the sugar transporter SGLT1 reached the cell surface; related rice bran compounds lowered after-meal blood sugar in mice. This is lab and animal work offered to explain the human after-meal results.
Histamine signalling and sleep in mice
In mouse studies by the group that ran the human sleep trial, the rice bran extract shortened the time to fall asleep and increased non-REM sleep by blocking the histamine H1 receptor, and had no sleep effect in mice lacking that receptor. This has not been shown in people.
Clinical trials
Randomized, placebo-controlled trial of 20 g a day of stabilized rice bran for 12 weeks (Cheng et al. 2010, Ann Nutr Metab)
28 adults with type 2 diabetes in Taiwan.
After-meal glucose and the area under the glucose curve fell by 14.4% and 15.7% from baseline in the rice bran group, and HbA1c also fell from baseline; these glucose results were reported against baseline rather than against placebo. Total and LDL cholesterol were 9.2% and 13.7% lower than in the placebo group, and adiponectin was 40% higher.
Randomized, controlled, parallel trial comparing 50 g a day of rice bran oil containing 0.05 g or 0.8 g of gamma-oryzanol for 4 weeks after a 2-week peanut oil run-in, from the Nestle Research Centre (Berger et al. 2005, Eur J Nutr)
30 men aged 38 to 64 with mildly raised cholesterol.
Both rice bran oils lowered total cholesterol by 6.3% and LDL by 10.5% compared with the peanut oil run-in, and the two oils did not differ, so extra gamma-oryzanol added nothing measurable. There was no separate control group during the rice bran oil phase.
Study 1: defatted rice bran added to double fiber intake for 5 weeks (parallel design). Study 2: 10-week randomized crossover in which rice bran oil made up a third of dietary fat versus a matched oil blend (Most et al. 2005, Am J Clin Nutr)
26 (study 1) and 14 (study 2) healthy adults with moderately raised cholesterol in the United States.
Defatted rice bran did not lower blood lipids. Rice bran oil lowered total cholesterol and cut LDL by 7% versus the control oil, with HDL unchanged. Because the fatty acids were matched, the authors attribute the effect to other oil compounds such as the unsaponifiable fraction.
Double-blind, randomized, placebo-controlled crossover test of a rice meal with olive oil plus 16.5 mg of rice bran triterpenoids versus olive oil alone; all authors were employed by Kao Corporation (Misawa et al. 2018, Food Nutr Res)
19 healthy adult men in Japan.
The rise in blood glucose over the first 1, 2 and 3 hours was significantly smaller after the triterpenoid meal, but the overall glucose curve only trended lower (P = 0.087). Insulin, GLP-1 and GIP did not differ. The effect was clearest in the 8 men with the largest glucose rises. This was a single test meal, not a long-term outcome.
Randomized, placebo-controlled trial of 500 mg a day of gamma-oryzanol during a 9-week periodized resistance training program (Fry et al. 1997, Int J Sport Nutr)
Moderately weight-trained men.
Both groups gained strength (bench press and squat) and jump power with no difference between them. Testosterone, cortisol, estradiol, growth hormone, insulin and blood lipids also did not differ. The authors concluded gamma-oryzanol did not influence performance.
Double-blind, placebo-controlled trial of 600 mg a day of gamma-oryzanol taken after training during 9 weeks of resistance exercise four days a week (Eslami et al. 2014, Indian J Med Res)
30 healthy young men (16 gamma-oryzanol, 14 placebo with lactose).
One-repetition maximum for bench press and leg curl rose more with gamma-oryzanol than with placebo. Body measurements and skinfolds did not differ. The sample was small, and the result conflicts with the earlier null trial at 500 mg a day.
Randomized, double-blind, placebo-controlled trial of 1,000 mg a day of an ethanol rice bran extract (standardized to 4.5 mg/g gamma-oryzanol, supplied by S&D Co.) for 2 weeks (Um et al. 2019, Sci Rep)
50 adults with sleep disturbance in Korea.
Compared with placebo, the extract shortened sleep latency (adjusted P = 0.047), increased total sleep time (P = 0.019) and improved sleep efficiency (P = 0.010) on polysomnography. Daytime sleepiness scores fell more than on placebo, but the extract group started out sleepier. Self-rated sleep quality (PSQI) and fatigue did not differ between groups. 42 of the 50 randomized were analyzed. No serious adverse events; mild events numbered 6 on the extract and 10 on placebo.
Randomized, double-blind, placebo-controlled trial of 1 g a day of a rice bran extract for 8 weeks; capsules supplied free by S&D Co., and the paper later received two published corrections (Huh et al. 2025, Am J Clin Nutr)
100 adults aged 19 to 75 with mild to moderate depressive symptoms in Korea (47 and 50 completed).
Clinician-rated Hamilton depression scores fell more with the extract (adjusted difference about 5.7 points versus placebo). PHQ-9 was lower only in the per-protocol analysis, the Beck depression and anxiety scales showed only trends, and other questionnaires and blood markers (BDNF, serotonin, dopamine, cortisol) did not differ. No adverse events were reported.