Chen et al. 2026, probiotic immune markers in athletes umbrella review

An umbrella review and re-analysis of five meta-analyses (69 RCTs, 3,413 athletes) found that probiotic supplementation significantly reduced TNF-α (ES = −0.59) and raised IgA and IFN-γ, but produced no meaningful change in IL-6, IL-8, or IL-10, with substantial heterogeneity across studies. The authors conclude probiotics can attenuate some pro-inflammatory responses and modestly enhance mucosal immunity, but optimal strain, dose, and duration remain unresolved. Moderate evidence.