Effect of Lactobacillus spp. Supplementation for Improving Muscle Health: A Systematic Review and Meta-Analysis

This systematic review and meta-analysis aimed to assess the quantitative effects of probiotic supplementation on improving muscle health, including muscle mass, lean mass, and hand grip strength, compared with a placebo. Databases were searched from PubMed, Embase, and Cochrane Library through January 2024. Researchers independently reviewed the studies using the quality assessment tool. Sensitivity analysis was conducted to clarify the statistical heterogeneity of the included studies. Funnel plots and Egger's test were used to assess the potential for publication bias in the meta-analysis. The overall estimates showed that muscle mass (standardized mean difference [SMD] = 0.29; 95% confidence interval [CI] = 0.03, 0.55; P = .03) and hand grip strength [SMD = 0.57; 95% CI = 0.09, 1.04; P = .02] were significantly increased. However, lean mass was not significantly changed (SMD = -0.05; 95% CI = -0.20, 0.10; P = .51). The subgroup studies demonstrated a significant size effect on muscle mass over 10 weeks of probiotic supplementation (SMD = 0.50; 95% CI = 0.02, 0.98; I² = 78%; P < .01). Moreover, the ethnicity subgroup comparison between Asian and non-Asian participants evaluating the effects of probiotic supplementation on muscle mass showed that Asian participants (SMD = 0.36; 95% CI = 0.03, 0.69) exhibited statistically significant heterogeneity (I² = 65%; P < .01) compared with non-Asian participants. Nevertheless, further studies are needed to elucidate the mechanism and evaluate the scientific evidence and clinical verification of probiotic supplementation. In conclusion, long-term probiotic supplementation with Lactobacillus spp. improved muscle function, increasing muscle mass and hand grip strength, especially among Asian participants, showing greater muscle strength gains from probiotic supplementation.