Effects of beetroot juice or dietary nitrate supplementation on swimming performance and physiological responses: a systematic review and meta-analysis

Beetroot juice (BRJ) and dietary nitrate supplementation have been widely investigated as ergogenic aids due to their potential to enhance exercise efficiency and performance through increased nitric oxide bioavailability. However, evidence regarding their effectiveness in swimming remains limited and inconsistent. This study evaluated whether acute or chronic BRJ or dietary nitrate supplementation improves swimming performance, post-exercise blood lactate concentration, and Rating of Perceived Exertion (RPE) in swimmers of different competitive levels. A systematic review and meta-analysis of randomized controlled trials was conducted following PRISMA 2020 guidelines and registered in PROSPERO (CRD420251106680). A comprehensive search until June 11, 2026 identified eligible randomized controlled trials comparing BRJ or nitrate supplementation with placebo or no supplementation in swimmers, and random-effects models were applied to analyze effects on time-trial performance, lactate responses, and RPE. Twelve studies met the inclusion criteria, of which nine contributed data to the quantitative meta-analysis ( n = 120 swimmers). BRJ or dietary nitrate supplementation did not significantly improve swimming time-trial performance in a multilevel meta-analysis including 12 comparisons from nine studies (SMD (standardized mean difference) = − 0.04, 95% CI − 0.21 to 0.13; p = 0.667) or post-exercise blood lactate concentration (k = 7; SMD = − 0.04, 95% CI − 0.27 to 0.19; p = 0.745). However, supplementation produced a small but statistically significant reduction in RPE (k = 7; SMD = − 0.33, 95% CI − 0.64 to − 0.001; p = 0.044). Subgroup analyses according to event duration did not identify significant differences between swimming effort categories. Overall, current evidence does not support a meaningful ergogenic effect of BRJ or dietary nitrate supplementation on swimming time-trial performance or post-exercise blood lactate responses, although supplementation may produce a small reduction in perceived exertion.