# Effects of probiotic supplementation on immune and inflammatory markers in athletes: an umbrella review and re-analysis of published meta-analyses of randomised controlled trials

## TL;DR

Probiotics may help reduce inflammation and boost immunity in athletes, based on a review of multiple studies.

## Contribution

This umbrella review provides a comprehensive synthesis and re-analysis of probiotic effects on immune markers in athletes.

## Key findings

- Probiotic supplementation significantly reduced pro-inflammatory TNF-α levels in athletes.
- Probiotics increased secretory IgA and IFN-γ, indicating improved mucosal immunity and immune response.
- No significant effects were found for IL-6, IL-8, and IL-10.

## Abstract

Intensive training and competition can compromise athletes’ immune function and elevate inflammatory responses. Although probiotics are widely studied as a nutritional intervention, existing meta-analyses have reported inconsistent findings regarding their efficacy. This umbrella review and re-analysis aimed to synthesize and evaluate the available evidence on the effects of probiotic supplementation on specific immune and inflammatory markers in athletes.

We systematically searched PubMed, Cochrane Library, Web of Science, EMbase, and Scopus for meta-analyses published up to December 1, 2025, and supplemented these with recent randomised controlled trials (RCTs) (up to December 15, 2025). Quality was assessed using Assessment of Multiple Systematic Reviews 2 (AMSTAR2) and Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) tools. Outcomes of interest included tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), interleukin-8 (IL-8), interleukin-10 (IL-10), immunoglobulin A (IgA) and interferon-gamma (IFN-γ). Overlap among studies was evaluated using the Graphical Representation of Overlap for OVErviews (GROOVE) tool, and data were re-analyzed using random- or fixed-effects models in Stata 15.0.

This umbrella analysis incorporated five meta-analyses (encompassing 69 RCTs) and one additional recent RCT, totaling 3,413 participants. Results showed that probiotic supplementation significantly reduced levels of the pro-inflammatory marker TNF-α (Effect Size (ES) = −0.59, 95% Confidence Interval (CI) [−0.94 to −0.24], P = 0.001). Probiotic supplementation significantly increased secretory IgA (ES = 0.30, 95% CI [0.03–0.57], P = 0.031) and IFN-γ levels (P < 0.01). In contrast, no significant effects were observed for IL-6 (ES = −0.09, 95% CI [−0.26 to 0.08]; P = 0.283), IL-8 (ES = −0.38, 95% CI [0.87 to 0.11], P = 0.132) and the anti-inflammatory cytokine IL-10 (ES = 0.15, 95% CI [−0.21 to 0.52], P = 0.411).

These robust results demonstrate that probiotic supplementation modulates exercise-induced immune disturbances in athletes by attenuating pro-inflammatory responses and enhancing mucosal immunity. These findings support its role as a strategic nutritional approach for immune protection. Future research should emphasize strain-specific efficacy and optimal dosing to enable personalized recommendations for athletes.