Effect of dietary nitrate on human muscle power: a systematic review and individual participant data meta-analysis

Study answer

What this study found

Dietary nitrate supplementation significantly increases maximal muscle power in humans. Pooled effect sizes: fixed effects g = 0.42 (95% CI 0.29-0.56; p = 6.31e-11); random effects g = 0.45 (95% CI 0.30-0.61; p = 1.06e-9); I2 = 22.8% (limited heterogeneity). Acute dosing yielded a larger effect (g = 0.54; 95% CI 0.37-0.71; p = 6.77e-12) than multi-day dosing (g = 0.22; 95% CI 0.01-0.43; p = 0.00363). Age, sex, and test modality did not significantly modify the effect. The average increase corresponds to about a 5% improvement in maximal power, which is likely to have practical athletic and…

Study & population

Randomized, double-blind, placebo-controlled, crossover trials; 19 studies; 268 participants (218 men, 50 women); ages varied; populations included healthy adults, older adults, Olympic-level athletes, and patients with heart failure; maximal power measured in non-fatigued state.

Intervention

Beetroot juice (dietary nitrate) ingestion; nitrate dose per session ranged from 6.4 to 15.9 mmol; most studies used a single acute dose before testing; some used multi-day dosing up to 6 days; forms included BRJ beverages and BRJ powder; one study used potassium nitrate (KNO3) as the nitrate source.

Key limitation

Not all studies reported the actual nitrate dose or biomarkers of nitric oxide bioavailability (11/19 and 10/19, respectively).

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Original abstract