Abstract
BACKGROUND: Exercise-induced inflammation, especially after intense or prolonged physical activity, can hinder recovery in athletes. Probiotic supplementation has been suggested as a potential method to modulate this inflammatory response by influencing the gut microbiota. However, the effects of probiotics on cytokine profiles following exercise remain unclear. This systematic review and meta-analysis aimed to assess the impact of probiotic supplementation on cytokine modulation in athletes aged 18-50 years following exercise. METHODS: Randomized controlled trials (RCTs) that administered probiotic supplementation for at least one week to athletes were included. Studies comparing probiotics to a placebo or no supplementation, with post-exercise cytokine levels as the primary outcome, were analyzed. A systematic search was conducted across four databases (PubMed (Medline), Scopus, Web of Science (WOS) and Cochrane), up to June 2024. Risk of bias was assessed using the McMaster Critical Review Form, and random-effects meta-analyses were performed to determine the impact of probiotic supplementation. RESULTS: A total of 19 studies involving 526 athletes from various endurance disciplines were included in the review. Probiotic supplementation significantly increased the anti-inflammatory cytokine interleukin-10 (IL-10) (SMD = 0.43; 95% CI 0.25-0.61; I(2) = 0%). However, no significant effects were observed for other cytokines, including IL-1β, IL-6, IL-8, TNF-α, or IFN-γ. Subgroup analyses supported the consistency of IL-10 findings across different exercise protocols, though substantial heterogeneity was observed for some cytokines. The variability in study designs, probiotic strains, dosages, and exercise modalities contributed to the mixed results. CONCLUSION: Probiotic supplementation appears to enhance anti-inflammatory responses post-exercise, particularly by increasing IL-10 levels, which may aid recovery in athletes. However, the evidence regarding its effects on pro-inflammatory cytokines remains inconclusive. Further well-designed RCTs are needed to clarify these effects and establish standardized protocols for supplementation.