The effects of dietary nitrate supplementation on endurance exercise performance and cardiorespiratory measures in healthy adults: a systematic review and meta-analysis.
Level 1 - systematic review of randomized trials
Systematic review and meta-analysis of placebo-controlled trials
PubMed 34243756 · doi:10.1186/s12970-021-00450-4
What was done
A systematic review and meta-analysis of studies searched across CENTRAL, MEDLINE, EMBASE, Web of Science, and CINAHL. Inclusion criteria required placebo-controlled trials evaluating dietary nitrate supplementation in adults performing endurance-based activity and reporting performance or surrogate physiological outcomes. Risk of bias was evaluated using the Cochrane tool, data were pooled with a random-effects model, and certainty was evaluated with GRADE. A total of 73 studies (n = 1,061) met the criteria.
What was found
Nitrate supplementation significantly improved power output (MD 4.6 watts, P < 0.0001), time to exhaustion (MD 25.3 s, P < 0.00001), and distance travelled (MD 163.7 m, P = 0.03). It significantly reduced VO2 (MD -0.04 L/min, P < 0.00001). No significant differences were observed for time trial performance, perceived exertion, work done, VO2max, or blood lactate levels.
Why it matters
This review synthesizes substantial trial data confirming that dietary nitrate enhances exercise efficiency and open-loop endurance capacity, though improvements may not reliably translate to fixed-distance time trials.
Limits
The abstract does not provide confidence intervals for the reported effect sizes. The average trial sample size was small (~15 participants per study). Results were not disaggregated in the abstract by participant fitness level, nitrate dosing protocol, or exercise modality.
Cited by
- supports Dietary nitrates from plants convert to nitric oxide, which causes vasodilation and improves endurance exercise performance.