Effects of polyphenol-rich, berry supplementation on exercise performance: A systematic review and meta-analysis

Summary: Background & Aims: Polyphenols are plant secondary compounds that possess antioxidant properties associated with preventing inflammation-mediated ailments such as cardiovascular disease and cancer. Recent studies hint at their capacity to enhance exercise performance. Berries, in addition to containing high amounts of essential vitamins and minerals, are extremely rich in polyphenols. Therefore, the aim of this systematic review and meta-analysis was to compile relevant human randomized controlled trials exploring the potential of polyphenol-rich berries to enhance exercise performance and associated biomarkers. Methods: The PubMed, Web of Science, and SPORTDiscus databases were searched using keywords related to berry supplementation, exercise performance, and biomarkers of performance. In total, 2374 articles were screened and 14 were included in the analysis. Results: The results indicate no statistically significant effect of berry supplementation on exercise performance and its associated biomarkers. However, there is a trend towards a positive pooled effect size of berry supplementation on time to exhaustion (SMD: 0.57, Z: 1.51, P-value: 0.13). Furthermore, all pooled effect sizes favor berry supplementation. Conclusions: Due to variations in testing protocols and biomarkers of interest among the studies included, no more than 7 articles were included for any given outcome measure. This underscores the necessity for additional high-quality randomized controlled trials (RCTs) to strengthen the evidence and allow for recommendations to be made regarding the performance enhancing effects of berry consumption. This systematic review and meta-analysis was registered on Open Science Framework (DOI 10.17605/OSF.IO/NCAVJ).