Rice bran extract eases depressive symptoms in adults

Daily intake of rice bran extract supplements (RBS) appears effective in reducing depressive symptoms in adults with mild-to-moderate symptom severity, reports a study, noting improvements reaching clinically relevant thresholds.

“Although biomarkers did not change after 8 weeks of RBS administration, RBS has the potential to provide an alternative option for alleviating depressed mood,” the researchers said.

One hundred adults (aged 19–75 years) with scores of 7–24 on the Korean version of the Hamilton Depression Rating Scale (K-HDRS) were randomized to receive 1 g/day of RBS or placebo for 8 weeks. Of the participants, 47 and 50 completed the intervention, respectively. [Am J Clin Nutr 2025;122:112-121]

The researchers evaluated the following at baseline and after 8 weeks: mood assessments using K-HDRS, the Korean version of the Beck Depression Inventory-II (K-BDI-II), the Patient Health Questionnaire-9 (K-PHQ-9), the Beck Anxiety Inventory (K-BAI), and other physiological scales. They also measured biomarkers such as serum brain-derived neurotrophic factor, serotonin, dopamine, and salivary cortisol.

Participants in the RBS group had greater improvements in K-HDRS scores at week 8 than those in the placebo group (p<0.001), with adjusted differences of –5.73 (95 percent confidence interval [CI], –7.07 to 4.39) in intention-to-treat (ITT) analysis and –5.95 (95 percent CI, –7.33 to –4.57) in per-protocol (PP) analysis. This corresponded to percent changes of –45.1 percent and –46.0 percent, respectively.

The research team also observed a trend toward greater reductions in the percent changes of K-BDI-II and K-BAI scores in the RBS vs placebo group. Participants on RBS also showed lower scores in K-PHQ-9 than those on placebo (p=0.026) after 8 weeks of treatment.

On the other hand, no significant differences were noted in other questionnaire scores or biomarker measurements between the two groups. In addition, no adverse events were documented.

Bioactive compound

In 2023, global rice production reached 720 million tons, with rice bran constituting 10 percent or >70 million tons. [https://app.amis-outlook.org/#/market-database/supply-and-demand-overview]

Rice bran extract is a great source of phytochemicals and bioactive compounds, including γ-oryzanol. Recent studies have shown the potential antidepressant effects of γ-oryzanol. For instance, a study by Kim and colleagues showed that 20-week supplementation with γ-oryzanol in mice ameliorated depressive-like behaviours and increased locomotor activity. [Mol Nutr Food Res 2024;68:e2300253]

Likewise, another study found that rice bran extract reduced depressive-like behaviours in colitis-induced rat models through mechanisms involving the gut–brain axis and Sirt1 signalling. [Food Chem Toxicol 2024;184:114386]

These findings showed the mechanistic rationale for studying RBS in human populations, according to the researchers.

“Notably, although our study demonstrated mood improvements in humans, corresponding changes in peripheral biomarkers such as brain-derived neurotrophic factor, serotonin, dopamine, and cortisol were not observed,” they said. “This highlights a translational gap between preclinical and clinical findings and suggests that mechanisms beyond monoamine modulation may be involved.” 

The typical range of γ-oryzanol content is 26–63 mg/100 g in rice and 10–154 mg/100 g in rice bran. In the current study, the ethanolic method yielded 439 mg/100 g of γ-oryzanol concentrations, exceeding previously reported values. [Int J Food Sci Nutr 2015;66:166-174; J Food Sci Technol 2019;56:2778-2786; J Agric Food Chem 1999;47:2724-2728; J Cereal Sci 2017;75:54-60]