Dietary Nitrates: What the Research Says About Beetroot Juice and Performance

Beetroot juice went from a niche endurance-athlete trick to a mainstream pre-workout supplement almost entirely on the back of one line of research: dietary nitrate lowers the oxygen cost of exercise. That finding is real, replicated, and mechanistically well-understood — but the size of the effect, who it actually helps, and how to dose it correctly get lost in most of the marketing copy on the bottle.

The Core Finding

The landmark study came from Lansley and colleagues, published in the Journal of Applied Physiology in 2011. Nine healthy subjects drank 0.5 liters of beetroot juice daily (providing 6.2 mmol of nitrate) or a nitrate-depleted placebo juice for six days, then completed treadmill and knee-extension exercise tests. The oxygen cost of both walking and moderate-intensity running dropped significantly with beetroot juice, and during high-intensity running, exercise tolerance improved by roughly 15%. The nitrate-depleted placebo was itself a methodological advance — it let researchers isolate nitrate specifically from everything else in beetroot juice, ruling out sugar content or other compounds as the explanation.

Earlier work by Bailey and colleagues in 2009 found a similar pattern: reduced oxygen cost during submaximal exercise and a longer time to exhaustion. Subsequent reviews, including meta-analyses pooling Bailey, Lansley, and later trials, converged on the same conclusion — dietary nitrate reliably improves exercise economy and, in many but not all protocols, extends time-to-exhaustion and time-trial performance. Sports science summaries citing the pooled trial data put the range at roughly a 25% increase in exercise time to exhaustion in some protocols, a 5% increase in sprint performance, and a 3% improvement in time-trial performance — meaningful margins in competitive endurance sport, where races are frequently decided by fractions of a percent.

The Mechanism

Dietary nitrate (NO3-) doesn't do much on its own. It has to be reduced to nitrite (NO2-) and then to nitric oxide, a process that depends on bacteria living on the back of the tongue. Those bacteria convert swallowed nitrate to nitrite, which is then further reduced to nitric oxide in the acidic environment of the stomach and in oxygen-poor tissue during exercise. Nitric oxide is a vasodilator, which improves blood flow and oxygen delivery to working muscle — but the more interesting finding from follow-up research by Bailey and colleagues is that nitrate supplementation also appears to improve mitochondrial efficiency, reducing the amount of oxygen needed to produce a given amount of ATP. That's a distinct mechanism from simple vasodilation, and it's the more likely explanation for why oxygen cost drops even during exercise intensities too low to be limited by blood flow.

The Mouthwash Finding

One of the more striking pieces of evidence for the oral-bacteria pathway comes from a study by Govoni and colleagues, which found that using antibacterial mouthwash after nitrate ingestion essentially abolished the rise in plasma nitrite — and with it, the performance benefit. Swallowing beetroot juice and immediately using strong antibacterial mouthwash defeats the mechanism entirely, since the oral bacteria that perform the first conversion step get killed off. It's a useful practical detail that most product marketing leaves out.

Dose and Timing

Effective doses in the research cluster around 5–9 mmol of nitrate (roughly 300–600mg), which corresponds to about 200–500ml of concentrated beetroot juice or an equivalent nitrate-standardized shot. Peak plasma nitrite typically occurs 2–3 hours after ingestion, which is the window most protocols time supplementation around before a race or hard training session. Some of the strongest effects in the literature come from multi-day loading protocols — six days of daily intake, as in the original Lansley study — rather than a single acute dose, though single-dose protocols timed correctly still show measurable benefits.

Whole foods rich in nitrate — beetroot, arugula, spinach, celery — work through the same pathway, but concentrated juice or standardized shots make it far easier to hit research-backed doses consistently. A concentrated product like Beet It Sport's nitrate shots is dosed specifically to match the amounts used in the exercise physiology trials, which is useful given how much a bunch of raw beets can vary in nitrate content depending on soil and growing conditions.

Who Actually Benefits

The effect size is not uniform across athletes. Several studies, including work reviewed by Jones in a 2014 Sports Medicine review, found the ergogenic effect of dietary nitrate tends to be larger in recreational and moderately trained athletes than in highly trained elite endurance athletes, who often already have well-optimized mitochondrial efficiency and nitric oxide signaling from years of training. That doesn't mean elite athletes see nothing — several national and Olympic-level endurance programs use nitrate protocols routinely — but the marginal gain is smaller relative to a less-trained person picking up the same habit.

Practical Takeaways

For endurance events — running, cycling, rowing, team-sport repeated-sprint efforts — a nitrate dose in the 300–600mg range, taken 2–3 hours before competition, with several days of loading beforehand if the schedule allows, matches what the trial evidence actually supports. Skip the antibacterial mouthwash on race day. And treat the bigger performance claims on supplement packaging with some skepticism — a 3–5% edge in trained athletes is real and useful, but it's not the transformative effect the marketing sometimes implies.