Effects of Beetroot Juice on Physical Performance in Professional Athletes and Healthy Individuals: An Umbrella...

Background: Beetroot juice, the most commonly used route of dietary nitrate supplementation, is theorized to enhance physical performance. However, its effects on different aspects of physical performance, different populations, and optimal supplementation strategies remain controversial. The purpose of this study was to investigate the effects of beetroot juice (nitrate-rich) on physical performance, to compare its effects between professional athletes and non-athletes (healthy individuals), and to determine the optimal supplementation strategy. Methods: A systematic search was conducted on the Web of Science, Embase, PubMed, Cochrane Database, SPORTDiscus, Scopus, and CINAHL databases. Reviewers conducted study screening and selection, data extraction, and assessment of methodological quality using the AMSTAR 2 tool. Fifteen meta-analyses were included in this Umbrella Review. A narrative and quantitative synthesis was performed. Standardized mean differences (SMD) and 95% confidence intervals (CI) were reported. Results: (1) Beetroot juice significantly improved muscle strength (SMD = 0.08, p < 0.001), but the effect size was negligible. (2) Aerobic Endurance: Beetroot juice significantly improved VO2max (SMD = 0.16, p = 0.033) in healthy adults; however, the effect size was negligible. (3) Lactate Tolerance: beetroot juice significantly improved TTE (SMD = 0.25, p = 0.034) and YO-YOIR1 (SMD = 0.27, p = 0.049) performance in healthy adults, but the effect size was small. (4) Subgroup analyses revealed significant population differences: professional athletes showed significant muscular strength benefits (SMD = 0.27, p = 0.007), whereas non-athletes had more pronounced aerobic endurance improvements (SMD = 0.26, p < 0.001), but the effect size was small. (5) Nitrate supplementation timing and dose-response analysis revealed that nitrate supplementation, whether administered 2-3 h before exercise or over a prolonged period (≥3 days), produces a significant enhancement in physical performance (p < 0.01). Notably, acute improvement only has a small effect size (SMD = 0.20), while the impact of chronic supplementation is essentially negligible (SMD = 0.13). A dosage of 8.3-16.4 mmol NO₃^- (515-1017 mg) showed a significant improvement (SMD = 0.14, p = 0.029), although the effect size was negligible. Conclusions: Acute (2-3 h pre-exercise) and chronic (≥3 days) supplementation with beetroot juice to achieve nitrate levels of 8.3-16.4 mmol (515-1017 mg/d) are recommended to enhance physical performance. Beetroot juice shows population-specific effects: proper beetroot juice supplementation improves muscular strength in professional athletes and aerobic endurance in non-athletes. Moreover, appropriate supplementation of beetroot juice can improve the lactate tolerance in healthy adults.