Effect of Polyphenol Supplementation on Post-Exercise Recovery in Adult Male Soccer Players: A Systematic Review.

Background/Objectives: Soccer involves high physiological demands that induce neuromuscular fatigue, muscle damage, inflammation, and oxidative stress, impairing recovery between training sessions and competitions. Polyphenols have been proposed as a nutritional strategy to modulate these responses; however, evidence in soccer players is limited and heterogeneous. This systematic review aimed to synthesize the evidence on the effects of polyphenol supplementation on post-exercise recovery in adult male soccer players. Methods: A systematic review was conducted following PRISMA guidelines, with a protocol registered in the Open Science Framework. Randomized controlled trials (RCTs) evaluating polyphenol supplementation versus placebo on post-exercise recovery in adult soccer players were included. Searches were performed in PubMed, Scopus, Web of Science, and the Cochrane Library up to April 2026. Risk of bias was assessed using RoB 2, and certainty of evidence using GRADE. Due to heterogeneity, a qualitative synthesis was conducted. Results: Eight RCTs were included. Interventions involved tart cherry juice, pomegranate juice, beetroot juice, curcumin, and tea extracts. Evidence was inconsistent for biomarkers of muscle damage, inflammation, and oxidative stress, with most studies reporting no significant differences versus placebo. In contrast, beneficial trends for perceptual outcomes, particularly reduced muscle soreness and improved subjective well-being, were mainly observed in studies using tart cherry juice, beetroot juice, and curcumin. Evidence for oxidative stress and functional recovery was limited and heterogeneous. Certainty of evidence was low for most outcomes and very low for oxidative stress and functional recovery. Conclusions: Polyphenol supplementation, particularly tart cherry juice, beetroot juice, and curcumin, may improve perceptual recovery in adult male soccer players, particularly by reducing muscle soreness and enhancing subjective well-being. However, evidence on physiological biomarkers and functional recovery remains inconsistent and of low certainty. Further well-designed RCTs are required to establish robust recommendations in competitive soccer.