Dietary nitrate (beetroot juice)
Evidence: moderate
Real but modest (~1-3%), best at moderate intensity and in less-trained runners, and blunted or absent in elites. Avoid antibacterial mouthwash around dosing.
Not medical advice
This is a general knowledge base, not medical or dietary advice. If you are injured, unwell or weighing up a supplement or a change to your diet, speak to a doctor, physiotherapist or registered dietitian who knows your situation.
Dietary nitrate, usually taken as concentrated beetroot juice, can improve endurance by lowering the oxygen cost of submaximal exercise. The nitric-oxide mechanism is well established, and the ergogenic effect has been studied heavily, but the honest verdict is that the effect is modest and conditional, not large or universal. The Australian Institute of Sport classes it Group A, its strongest evidence tier, though that rating deserves the scrutiny set out below.
Nitrate is converted to nitrite and then to nitric oxide through a pathway that depends on bacteria in the mouth (McMahon et al. 2017). The effective dose is about 6 to 8 mmol, roughly 350 to 500 mg, in one 70 ml concentrated shot, taken two to three hours before exercise, or daily for several days; more than about 10 to 12 mmol adds nothing.
The effect size is the part the marketing tends to skip. Nitrate is more reliably ergogenic for time to exhaustion than for time-trials, with typical gains around 1 to 3%, and it works best at moderate intensities and in less-trained people (McMahon et al. 2017). In highly trained endurance athletes, those with a VO₂max above roughly 65, the benefit is blunted or absent, a clear example of individual variation. Because the conversion depends on oral bacteria, antibacterial mouthwash abolishes the effect, so it should be avoided around dosing (McMahon et al. 2017).
The practical reading: a genuine, cheap, food-based aid with a modest edge for recreational and sub-elite runners at moderate intensity, and little to offer the elite.
Research quality and who funds it
The Group A badge deserves a sceptic’s scrutiny, on both quality and funding. On quality: nitrate is heavily studied, with more than twenty systematic reviews (nitrate umbrella review), so it is not under-researched. But most trials are small and short, run on young, recreationally active men, the effects are small and inconsistent, and the benefit concentrates in recreational athletes rather than elites. The rating reflects a large pile of small studies showing a modest effect, not a few decisive ones.
On funding: a large share of the foundational performance research comes from one group, at the University of Exeter, which has an openly acknowledged commercial relationship with Beet It (James White Drinks): the standardised beetroot shots used as the research supplement across the field were co-developed with the researchers, and an IOC statement leaned on around a dozen of the group’s papers (Exeter–Beet It link). Individual studies usually declare no conflict, and the underlying nitric-oxide biology is solid work from independent labs, so this is not a case of fabricated results. But a performance literature concentrated in a commercially linked group, showing a small effect that shrinks under tighter control and in better athletes, is exactly the pattern to read cautiously. It does not overturn the modest verdict above; it explains why the marketing sounds more confident than the data justify.
If you want to try it
Use a concentrated beetroot “shot” standardised to about 6 to 8 mmol of nitrate, taken roughly 2 to 3 hours before the effort, or daily for a few days beforehand. Whole beetroot juice and green leafy vegetables also supply nitrate but the dose is harder to pin down. Skip antibacterial mouthwash around dosing, since it kills the oral bacteria the effect depends on. Expect a modest edge at best, most likely if you are not already highly trained, and trial it first, partly because it harmlessly turns urine pink.