Sports nutrition research has a well-documented blind spot: women make up only 4–13% of participants across sports-science studies, so most nitrate-supplementation research — including the original beetroot-juice-for-endurance findings — comes almost entirely from male athletes. A 2025 randomized controlled trial published in Nutrients set out to close that gap, specifically testing beetroot juice’s effect on aerobic performance in female endurance athletes.
Why Beetroot Juice, Specifically
Beetroot juice is naturally high in dietary nitrates, which the body converts through a nitrate–nitrite–nitric oxide pathway into nitric oxide — a molecule that dilates blood vessels and improves oxygen delivery to working muscle. That pathway is particularly active under the low-oxygen, low-pH conditions of intense exercise, which is why nitrate supplementation has drawn specific interest for endurance and high-intensity performance.
How the Trial Was Run
Eighteen healthy female endurance athletes (mean age 22.9) completed two cardiopulmonary exercise tests on a cycle ergometer, a week apart. Before the second test, the beetroot juice group drank 50 mL of concentrate providing about 6.2 mmol of nitrate; the placebo group drank an equivalent nitrate-free version. Participants using hormonal contraception were excluded and testing was scheduled around the follicular phase of the menstrual cycle, since hormonal fluctuations are known to affect nitric oxide production and how the body responds to dietary nitrates.
What Changed After Beetroot Juice
VO₂ Max
Maximal oxygen consumption increased by 4.82% in the beetroot juice group (from 35.24 to 36.94 mL·min⁻¹·kg⁻¹), while the placebo group’s VO₂ max slightly declined (−0.57%). VO₂ max is one of the most established markers of aerobic fitness, and improvements in this range are considered practically meaningful for endurance performance.
Breathing and Heart Rate Efficiency
The beetroot group also showed a significantly more efficient ventilatory pattern: minute ventilation decreased (meaning less breathing effort was needed for the same exercise intensity), the ventilatory equivalent for oxygen (VE/VO₂) improved by 9.52%, and heart rate during exercise decreased significantly — all signs of the cardiovascular and respiratory systems doing more work per breath and per heartbeat. The placebo group moved in the opposite direction on every one of these measures.
Why This Might Matter More for Women
The researchers note that women’s muscle tissue tends to have a higher proportion of oxidative fiber type and a more efficient capacity to metabolize nitrates than men’s, which may mean female athletes see a proportionally larger benefit from nitrate supplementation — a hypothesis this study’s results are consistent with, though the authors are careful to note the sample size (18 participants) means the findings need replication in larger cohorts.
The Bottom Line
In this randomized trial, a single 50 mL dose of nitrate-rich beetroot juice taken two and a half hours before exercise produced a measurable, multi-marker improvement in aerobic performance in female endurance athletes — higher VO₂ max, more efficient oxygen use, and lower cardiovascular strain at the same workload. The effect sizes were meaningful even in a moderately-trained population, and the study adds real data to a research area where female athletes have historically been underrepresented.
References
[1] Neteca, J.; Veseta, U.; Liepina, I.; Volgemute, K.; Dzintare, M.; Babarykin, D. “Effect of Beetroot Juice Supplementation on Aerobic Capacity in Female Athletes: A Randomized Controlled Study.” Nutrients 2025, 17, 63. https://doi.org/10.3390/nu17010063 (open access)
