Probiotic Lactobacillus acidophilus JYLA-126 improves metabolic outcomes in polycystic ovary syndrome: a randomized controlled trial

Background: Polycystic Ovary Syndrome (PCOS), a prevalent endocrine disorder in women, is characterized by insulin resistance (IR), obesity, and gut dysbiosis, driving metabolic and reproductive dysfunction. Metformin, though first-line for PCOS, is often limited by gastrointestinal intolerance, reducing adherence. Thus, safe adjuncts are urgently needed to improve metabolic control and treatment tolerability. This trial evaluated whether Lactobacillus acidophilus (L. acidophilus) JYLA-126 could enhance metformin's efficacy and tolerability in women with PCOS.Methods: In this 12-week randomized controlled trial, 100 women (18–40 years) with PCOS, IR, and obesity were randomized to receive metformin plus placebo or metformin plus L. acidophilus JYLA-126. Outcomes included anthropometrics, menstrual regularity, metabolic/hormonal profiles, gut microbiota, and adverse events. Analyses involved t-tests, ANOVA, and Pearson correlations.Results: Both groups improved with metformin, but the probiotic group showed greater weight loss and metabolic benefits, including lower fasting glucose (4.97 ± 0.53 vs. 5.53 ± 0.84 mmol/L, p < 0.001) and HOMA-IR (3.35 ± 1.48 vs. 4.40 ± 2.29, p < 0.05) at 1 month, and more favorable hormonal changes (LH: 7.68 ± 1.15 vs. 8.92 ± 1.79 U/L; AMH: 6.40 ± 1.88 vs. 7.90 ± 2.39 ng/mL, p < 0.05) at 3 months. Favorable shifts in gut microbiota (increased Faecalibacterium and Ruminococcus, reduced Collinsella) were also observed. The combination reduced gastrointestinal side effects, and microbiota changes correlated with PCOS/IR biomarkers.Conclusion: L. acidophilus JYLA-126 supplementation may provide additional metabolic, hormonal, and gastrointestinal benefits to metformin therapy in PCOS, supporting its potential as a useful nutritional adjunct.