Effects of Beetroot-Based Supplements on Muscular Endurance and Strength in Healthy Male Individuals: A Systematic Review and Meta-Analysis

The aim of this study was to systematically review the current literature and analyze the effects of beetroot-based supplements (BRS) on muscular performance. Randomized controlled trials that assessed the acute or short-term effects of BRS administration on muscular endurance and/or strength in healthy male individuals were retrieved from PubMed, EMBASE, CENTRAL, and Web of Science databases from inception to February 20th, 2023. In addition, we also searched preprint papers in medRxiv.org, bibRxiv.org; thesis and dissertations included in oatd.org; and clinical trials published in ClinicalTrials.gov. Data extraction, risk of bias, and study quality were assessed by 2 authors. Meta-analyses and subgroup analyses of standardized mean differences (SMD) were performed using a random-effects model. A total of 1486 records were identified in the databases and 2 were obtained by manual search in the reference list. Of those, 27 studies attended eligibility criteria and composed this systematic review. BRS administration resulted in a positive effect on muscular endurance (SMD: 0.31; 95% confidence interval (CI): 0.10 to 0.51; p < 0.01; n = 16 studies). There was an overall significative effect for muscular strength (SMD: 0.26; 95% CI: 0.03 to 0.48; p < 0.05; n = 18 studies), but a subgroup analysis showed that significant effects were found when strength was measured in a fatigued (SMD: 0.64; 95% CI: 0.25 to 1.03; p < 0.01), but not resting state. BRS administration have a small ergogenic effect on muscular endurance and attenuate the decline in muscular strength in a fatigued state in healthy male individuals.