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
