Dietary Nitrate Supplementation and Exercise Performance in Athletes: A Systematic Review and Meta-Analysis of Randomised Controlled Trials

Background/Objectives: Dietary nitrate supplementation improves exercise performance in recreationally active individuals, but efficacy in athletes remains debated. This meta-analysis evaluated the effects of dietary nitrate supplementation on six exercise performance and physiological/perceptual outcomes—peak power (PP), mean power (MP), maximal oxygen uptake (VO2max), heart rate (HR), blood lactate (LAC), and rating of perceived exertion (RPE)—in athletes across diverse sports and protocols. Methods: Forty-five randomized, placebo-controlled trials involving 659 healthy athletes (Tier 2 or higher) were included. Random-effects meta-analyses calculated pooled Hedges’ g. Subgroup, sensitivity, and publication bias analyses were conducted. Results: No statistically significant overall effect was found for any of the six outcomes (all p > 0.05). In exploratory subgroup analyses, PP showed a positive effect in male-only studies (g = 0.29, 95% CI 0.02 to 0.56, p = 0.04), but the interaction with mixed-sex studies was not significant (p = 0.11). Beetroot and nitrate salts did not differ in VO2max. And trim-and-fill imputed five studies, reducing this estimate to zero. Subgroup analyses by sport type and exercise type (endurance, intermittent team sports, strength/power) revealed no significant differences. Conclusions: Dietary nitrate supplementation produced no statistically significant pooled ergogenic effects in athletes. Any potential benefit appears small and context-dependent, and the possible role of vascular endothelial function in high-performance athletes warrants further investigation. The absence of statistically significant effects should not be regarded as definitive evidence of no effect.