Probiotic supplementation in reducing exercise-induced gastrointestinal symptoms in endurance athletes: an integrative review

Endurance exercise can cause significant disturbances in the gastrointestinal tract, known as “exercise-induced gastrointestinal syndrome.” These disturbances may lead to gastrointestinal symptoms and affect athletes’ performance and health. This integrative review evaluated the effect of probiotic supplementation in reducing gastrointestinal symptoms associated with endurance exercise, discussing possible underlying mechanisms. The review was conducted in August 2024 across four electronic databases (PubMed, Scopus, Cochrane Library, ScienceDirect), using a search strategy based on the PICO criteria. The search terms included: “Endurance athletes” OR “Elite athletes” AND “Probiotic” AND “Gastrointestinal” OR “Gut” AND “Symptoms” OR “Health” OR “Disorder.” Randomized controlled clinical trials involving adult endurance athletes were included. A total of 265 articles were identified, of which nine met the eligibility criteria. The interventions involved supplementation with various strains of probiotic bacteria and produced different effects in both the number and severity of GI symptoms during training periods, reducing the number of reported incidents among participants. Due to methodological differences among the studies, it was not possible to determine the best supplementation protocol. Most studies did not report promising outcomes regarding GI-related symptom parameters, yielding heterogeneous results. The methodological variability across studies hinders result interpretation and introduces confounding factors in the analysis. Thus, probiotic supplementation should be approached with caution, respecting GI symptoms and the individual response of each athlete.