Although over 100 studies and reviews have examined the ergogenic effects of dietary nitrate (NO3-) supplementation in young, healthy men and women, it is unclear if participant and environmental factors modulate the well-described ergogenic effects-particularly relevant factors include biological sex, aerobic fitness, and fraction of inspired oxygen (FiO2) during exercise. To address this limitation, the literature was systematically reviewed for randomized, crossover, placebo-controlled studies reporting exercise performance outcome metrics with NO3- supplementation in young, healthy adults. Of the 2033 articles identified, 80 were eligible for inclusion in the meta-analysis. Random-effects meta-analysis demonstrated that exercise performance improved with NO3- supplementation compared with placebo (d = 0.174; 95% confidence interval (CI), 0.120-0.229; P < 0.001). Subgroup analyses conducted on biological sex, aerobic fitness, and FiO2 demonstrated that the ergogenic effect of NO3- supplementation was as follows: 1) not observed in studies with only women (n = 6; d = 0.116; 95% CI,-0.126 to 0.358; P = 0.347), 2) not observed in well-trained endurance athletes (≥65 mL·kg-1·min-1; n = 26; d = 0.021; 95% CI,-0.103 to 0.144; P = 0.745), and 3) not modulated by FiO2 (hypoxia vs normoxia). Together, the meta-analyses demonstrated a clear ergogenic effect of NO3- supplementation in recreationally active, young, healthy men across different exercise paradigms and NO3- supplementation parameters; however, the effect size of NO3- supplementation was objectively small (d = 0.174). NO3- supplementation has more limited utility as an ergogenic aid in participants with excellent aerobic fitness that have optimized other training parameters. Mechanistic research and studies incorporating a wide variety of subjects (e.g., women) are needed to advance the study of NO3- supplementation; however, additional descriptive studies of young, healthy men may have limited utility.
- Beetroot Juice
- Dietary Nitrate
- Exercise Performance
- Sex Differences
ASJC Scopus subject areas
- Orthopedics and Sports Medicine
- Physical Therapy, Sports Therapy and Rehabilitation