A review of 38 trials examines who may benefit most from beetroot juice, and why elite athletes should interpret the evidence with caution.

Study: Effects of beetroot juice supplementation on maximal oxygen uptake during aerobic exercise: a systematic review and meta-analysis. Image Credit: Nungning20 / Shutterstock

In a recent systematic review and meta-analysis published in the journal Frontiers in Nutrition, researchers in the Republic of Korea synthesized evidence from placebo-controlled trials of beetroot juice supplementation and peak oxygen uptake (VO2peak) or maximal oxygen uptake (VO2max) during aerobic exercise.

Beetroot juice has attracted substantial interest as a sports nutritional supplement due to its high levels of inorganic nitrate. Nitrate is converted to nitrite, which is then converted to nitric oxide (NO). NO plays an important role in oxygen delivery, muscle contraction, and vascular function. These effects provide a biological rationale for, but do not establish, the possibility that beetroot juice may improve aerobic exercise performance.

VO2max is a widely used measure of aerobic capacity and cardiovascular fitness. Nevertheless, the criteria for confirming a true VO2max are not met or reported in many trials. In such cases, the highest oxygen uptake is described as VO2peak. However, prior reviews have often combined evidence on VO2max or VO2peak with broader exercise-performance outcomes and have not always distinguished verified VO2max from VO2peak.

About the Study

In the present study, researchers investigated the effects of beetroot juice supplementation on VO2max or VO2peak during aerobic exercise in healthy adults and trained athletes. First, they conducted a literature search across Scopus, PubMed, SPORTDiscus, Google Scholar, Cochrane CENTRAL, and Web of Science from database inception to January 31, 2026. Eligible studies were randomized controlled or randomized crossover placebo-controlled trials that used beetroot-derived nitrate or beetroot juice as the intervention and measured VO2peak or VO2max during incremental or graded aerobic exercise.

Studies involving clinical populations that could confound aerobic-capacity testing, non-beetroot sources of nitrate, insufficient data, or beetroot juice combined with other interventions were excluded. Search results were deduplicated and screened at the title and abstract levels. Full texts of articles were examined for inclusion. Relevant data, including study and participant characteristics, testing protocols, intervention details, outcome definitions, and results, were extracted.

The Cochrane risk-of-bias tool for randomized trials was used to assess the methodological quality and risk of bias of the studies. The study's outcome was relative or absolute VO2max or VO2peak, with relative values preferred where available for cross-study comparisons. Standardized mean differences (SMDs) were calculated as Hedges' g for each study. The DerSimonian–Laird random-effects model was used for the meta-analysis. The I2 statistic and Cochran's Q test were used to assess heterogeneity across studies.

Prespecified subgroup analyses examined supplementation duration, training status, nitrate dose, and exercise-testing modality. Sex was also a prespecified factor, although sex-stratified results were not reported. Sensitivity analyses were conducted to evaluate the robustness of the results. Funnel plots, Egger's test, and trim-and-fill analysis were used to assess publication bias. The certainty of evidence was evaluated using the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) framework.

Findings

The literature search identified 1,193 records. Following deduplication, title and abstract screening, and full-text analysis, 44 studies were included in the qualitative analysis and 38 in the meta-analysis. These 38 studies, comprising 703 participants, were published from 2009 to 2025. Studies differed in participant training, nitrate dose, exercise-testing modality, and supplementation duration. Nitrate-depleted beetroot juice was the placebo in most studies.

Twenty-two studies had a low risk of bias, while 16 had some concerns. The meta-analysis revealed a small but significant effect of beetroot juice supplementation on VO2max or VO2peak relative to placebo, with an SMD of 0.24, a 95% confidence interval (CI) of 0.11 to 0.37, and p \< 0.001. Moderate heterogeneity was observed (I2 \= 48.3%). Subgroup analyses showed that both chronic and acute supplementation were associated with significant improvements in VO2max or VO2peak. However, chronic supplementation had a slightly larger effect, while acute supplementation had a smaller effect. Because heterogeneity was higher in the chronic subgroup, this difference does not establish chronic protocols as superior overall.

The largest effect of supplementation was noted in recreationally active participants. No statistically significant effect was detected in elite or highly trained athletes. Standard nitrate doses ranging from 6.4 mmol to 12.8 mmol yielded the most consistent effects, whereas lower doses were not significant. Higher doses were significant but did not show a clearly superior effect over the standard-dose range. Regarding exercise-testing modality, treadmill and cycle-ergometer studies showed significant effects, with no significant difference between the two modalities.

The robustness of the primary estimate was confirmed in a leave-one-out analysis. Funnel plots revealed mild asymmetry, while Egger's test indicated significant small-study effects. After trim-and-fill adjustment, which imputed five potentially missing studies, the pooled effect was attenuated but remained significant, with an SMD of 0.19 and a 95% CI of 0.07 to 0.31. Overall, the certainty of evidence was rated as moderate. Certainty was high among recreationally active participants but low among highly trained athletes. The evidence base was predominantly male, and the pooled analysis combined verified VO2max and VO2peak values, limiting generalizability and precision.

Conclusions

In sum, beetroot juice supplementation was found to have a small and significant effect on VO2max or VO2peak during aerobic exercise. This indicates a modest benefit rather than a uniform or substantial improvement across populations. Moreover, current evidence did not clearly demonstrate a benefit among highly trained or elite athletes. Overall, the certainty of evidence was moderate, and practical recommendations, especially for elite athletes, should be made with caution.