Effect of probiotics or synbiotics on skeletal muscle in older adults: a systematic review and meta-analysis of randomized controlled trials

Probiotics and synbiotics have been widely used to modulate gut microbiome, which is associated with skeletal muscle aging and overall health in older adults. The aim of this systematic review and meta-analysis was to verify the effect of probiotics and synbiotics on muscle mass, muscle strength, physical performance, and quality of life (QOL) in older adults. PubMed, Embase, and Web of Science were searched from inception to Nov. 2023 for randomized controlled trials (RCTs). RCTs were identified that investigated the effects of supplementations containing probiotics or synbiotics on parameters of muscle mass, muscle strength, physical performance, and QOL in elderly adults. Standardized mean difference (SMD) with their 95%CI was used for the synthesis of the results. In total, 15 studies were included in this review. The administration of probiotics and synbiotics moderately improved muscle strength (k = 7, SMD = 0.667, 95%confidence interval (CI): 0.317–1.017, I² = 72.5%, p = 0.001) and physical performance (k = 6, SMD = 0.597, 95%CI: 0.118–1.075, I² = 80.6%, p < 0.001), whereas no significant effect was found on muscle mass (k = 8, SMD = 0.067, 95%CI: –0.090–0.225, I² = 26.0%, p = 0.221) and QOL (k = 7, SMD = 0.421, 95%CI: –0.054–0.895, I² = 86.2%, p < 0.001) in older adults. The subgroup analysis showed better performance in studies conducted in Asia, providing extra nutritional supplementation and exercise programs, and using long-term treatment, with more positive effects or lower heterogeneity. Furthermore, some evidence about the effects on gut microbiome, intestinal permeability, and immune and nutritional status was reported. This systematic review and meta-analysis demonstrate the safety and effectiveness of probiotics and synbiotics in improving muscle function among older people, possibly through alleviating intestinal permeability, immunosenescence, and nutritional status. Systematic review registration: https://www.crd.york.ac.uk/prospero/, Identifier: CRD 42023428400.