Probiotic modulation of the athletic gut: Implications for intestinal barrier function, immunity and exercise-related stress

Background Physical activity is associated with multiple systemic adaptations, some of which appear to be mediated by the gut microbiota. In athletes, especially those engaged in endurance sports, intense training may alter gut barrier function, immune responses and gastrointestinal homeostasis. In this context, probiotics have attracted growing interest as a potential nutritional strategy to support gut health and exercise adaptation. This narrative review aims to summarize current evidence on the interactions between gut microbiota, physical activity and probiotic supplementation in athletes, with particular attention to gastrointestinal health, immune modulation, oxidative stress and exercise-related physiological responses. Materials and methods A narrative review of the literature published between 2005 and 2025 was conducted using major scientific databases, including PubMed, Scopus and Web of Science. The literature was selected on the basis of relevance to the topic, with emphasis on studies involving athletes, endurance exercise, gut microbiota and probiotic use. Results The available literature suggests that regular physical activity may influence gut microbiota composition and metabolic activity, while probiotic supplementation may help support gastrointestinal integrity, modulate immune and inflammatory responses and reduce selected exercise-related symptoms in athletes. However, findings remain heterogeneous because of differences in study design, probiotic strains, dosages, intervention duration and athlete populations. Conclusions Probiotic supplementation may represent a promising supportive strategy for modulating the athletic gut, particularly in relation to intestinal barrier integrity, immune regulation and exercise-associated physiological stress. Nevertheless, current evidence remains heterogeneous and further well designed studies are needed to clarify strain-specific effects and their relevance to athletic performance and recovery.