Can Probiotic Supplementation Improve Bone Mineral Density in Postmenopausal Women? A Systematic Review

Background: Postmenopausal women face a high risk of osteoporosis, often necessitating long-term management strategies beyond conventional pharmacological treatments. The emerging "gut-bone axis" theory suggests that gut microbiota significantly influences bone metabolism, positioning probiotic supplementation as a potential novel intervention for bone health. Aim: This systematic review aims to evaluate the effects of probiotic supplementation on total hip and lumbar spine bone mineral density (BMD) in postmenopausal women. Methods: We searched PubMed, Web of Science, and the Cochrane Library databases for relevant randomized controlled trials (RCTs) from their inception to November 2025. Study quality was assessed using the Cochrane risk of bias tool. Data were pooled using standardized mean differences (SMD) with 95% confidence intervals (CIs) in a random-effects model, and heterogeneity was quantified using the I² statistic. Summary: Four RCTs involving 461 postmenopausal women were included. The pooled analysis showed a non-significant positive trend for both total hip BMD (SMD = 0.60, 95% CI: -0.17 to 1.38) and lumbar spine BMD (SMD = 0.48, 95% CI: -0.03 to 1.00), with considerable heterogeneity (I² = 95% and 89%, respectively). Current evidence suggests a potential beneficial effect of probiotics on BMD, likely mediated through gut microbiota regulation, estrogen metabolism, and inflammatory modulation. However, the conclusions are limited by the small number of studies, high heterogeneity, and varying intervention protocols. Future large-scale, long-term RCTs with standardized protocols are warranted to confirm these findings and elucidate optimal probiotic strategies.