Effects of GABA-enriched rice germ extract fermented by Lactobacillus brevis BJ20 on stress symptoms and related biomarkers in adults: a randomized, double-blind, placebo-controlled trial

Stress is a growing public health concern, and nutritional approaches have gained increasing attention for improving mental well-being. Fermentation enhances the bioactive γ-aminobutyric acid (GABA) content of agric ultural materials. This 8-week, randomized, double-blind, placebo-controlled trial evaluated the efficacy and safety of a novel GABA-enriched rice germ extract (RG30), produced by Lactobacillus brevis BJ20 fermentation, in 80 adults with mild-to-moderate perceived stress. Participants received 500 mg/day RG30 (120 mg GABA) or placebo. RG30 supplementation significantly reduced Stress Response Inventory scores compared with placebo (adjusted mean difference: −5.39; 95% CI: −10.25, −0.54; p = 0.035) and improved quality of life (EuroQol VAS, p ≤ 0.002) after 8 weeks. Among secondary outcomes, plasma serotonin levels showed relative preservation in the RG30 group with placebo ( p = 0.036). No serious adverse events occurred. RG30 represents a safe, fermented, plant-derived functional ingredient that alleviates stress symptoms and enhances quality of life.