Gut microbiota and exercise: A systematic review of interventions and evidence limitations.

This systematic literature review assessed whether nutritional supplement, dietary, and exercise interventions influence gut microbiota and subsequent exercise performance. Following PRISMA guidelines, a comprehensive search was conducted across five databases (Ovid MEDLINE, EMBASE, CINAHL Complete, Web of Science, and Scopus) up to February 2025. Included studies involved healthy, active adults undergoing nutrient supplementation, dietary, and/or exercise interventions with a control or placebo comparator. Outcomes included faecal bacterial composition (α-diversity, relative abundance), short chain fatty acids (SCFA), in adjunct with exercise performance (i.e., time-trial, time to exhaustion, maximal strength). Eighteen studies met the inclusion criteria. Due to methodological heterogeneity, a descriptive synthesis was performed. Changes in faecal microbiota diversity and composition were highly variable and largely minimal. SCFA outcomes were infrequently assessed; only one study reported a significant increase in faecal acetate concentration following yoghurt supplementation containing Bifidobacterium animalis subsp. lactis BL-99. Only seven studies examined the relationship between changes in faecal bacterial profile and performance outcomes, with limited or inconclusive findings. No consistent performance benefits were observed in relation to microbiota changes. Risk of bias and methodological limitations were common, including variation in interventions, outcome measures, and microbiota analysis methods. Taken together, the current evidence base remains too limited and heterogeneous to draw firm conclusions about the efficacy of microbiota-targeted interventions for enhancing exercise performance in healthy, active adults. Future studies employing standardised methods, mechanistic outcome measures, and longitudinal designs may help clarify the potential of microbiota modulation as a performance-enhancing strategy.