The short version
- Three days of dietary nitrate reduced the oxygen cost of submaximal cycling from 2.98 to 2.82 litres per minute and raised gross efficiency from 19.7% to 21.1% in nine well-trained men.
- Across 21 subjects with VO2peak spanning 28.2 to 81.7 mL/kg/min, the reduction in oxygen cost and the 3km time-trial improvement both correlated inversely with aerobic fitness (r=0.80 and r=0.76).
- Pooling 123 studies and 1,705 participants, nitrate improved exercise performance with a standardised mean difference of 0.101, a small effect.
- In that meta-analysis nitrate salt supplements were not effective, while beetroot juice and a high-nitrate diet were, and the effect was clearest for efforts lasting 2 to 10 minutes.
- An antibacterial mouthwash abolished the conversion of dietary nitrate to nitrite in saliva and markedly attenuated the plasma nitrite rise in seven volunteers.
Beetroot is marketed with photographs of very fit people. The literature suggests those are the people it does least for.
The finding that started it
In 2007, Larsen and colleagues gave nine healthy, well-trained men sodium nitrate at 0.1 mmol/kg/day, or an equal amount of sodium chloride, for three days each in randomised double-blind crossover, then tested them on a cycle ergometer.
Oxygen cost at submaximal exercise fell. Averaged over the four lowest work rates, VO2 dropped from 2.98 to 2.82 L/min (P<0.02) and gross efficiency rose from 19.7% to 21.1% (P<0.01). Heart rate, lactate, ventilation and respiratory exchange ratio did not differ.
That is a strange and interesting result. Doing the same work on less oxygen is normally what months of training buys you. A dietary anion produced a slice of it in three days.
The catch, and it is a big one
Porcelli and colleagues recruited 21 people whose VO2peak spanned 28.2 to 81.7 mL/kg/min — sedentary through to genuinely elite — and gave them six days of nitrate-containing water at 5.5 mmol/day or nitrate-free water, crossover, double-blind.
The reduction in oxygen cost correlated negatively with aerobic fitness (r=0.80, P<0.0001). So did the improvement in a 3km running time trial (r=0.76, P<0.0001). Fitter subjects also showed smaller rises in plasma nitrate and nitrite from the same dose.
The better you already are, the less it does. If you are buying beetroot because a professional cyclist endorses it, you are buying it on the strength of the population in whom it performs worst.
What pooling everything says
A systematic review with meta-regression covering 123 studies and 1,705 participants found nitrate improved exercise performance with a standardised mean difference of 0.101 (95% CI 0.051 to 0.151, P<0.001). That is a small effect, and worth calling small.
The moderators are where the practical value sits:
- Form matters. Nitrate salt supplements were not effective (P=0.629). Beetroot juice was (P<0.001), as was a high-nitrate diet (P=0.005).
- Duration matters. The effect was clearest for efforts lasting between 2 and 10 minutes.
- Timing matters. The most effective acute dose was 5 to 14.9 mmol taken at least 150 minutes before exercise.
- Loading matters. For protocols of two days or more, the optimal dose was 5 to 9.9 mmol a day, with an inverse dose-response above that.
Two and a half hours before, not ten minutes before. Juice or vegetables, not a salt capsule. And if your event is an hour long, the window where nitrate looks best is not your window.
The mouthwash problem, which is genuinely strange
Dietary nitrate only becomes useful after bacteria on your tongue reduce it to nitrite. Govoni and colleagues gave seven volunteers a nitrate load with and without a chlorhexidine antibacterial mouthwash beforehand. The mouthwash abolished the conversion to nitrite in saliva and markedly attenuated the rise in plasma nitrite, while leaving nitrate levels themselves untouched.
The meta-analysis found the same thing at population scale: practices harmful to oral bacteria decreased the ergogenic effect of nitrate. If you gargle antibacterial mouthwash and then drink beetroot juice, you have paid for the juice and disabled the mechanism.
What we would actually say
If you are recreationally fit rather than elite, if your effort sits in the two-to-ten-minute band, and if you can take it around 2 to 3 hours beforehand, beetroot is one of the few supplements in this category with a genuinely coherent evidence base. Use juice or concentrate rather than a nitrate salt. Skip the antibacterial mouthwash that day.
If you are an elite endurance athlete, the correlations say to expect less, not more. And if you are buying beetroot to fix an afternoon energy dip at a desk, this is the wrong shelf entirely — nitrate's evidence is about the oxygen cost of exercise, not about alertness. An electrolyte drink is a similarly poor fit for that problem, for similar reasons.
Good questions
Does beetroot juice actually improve performance?
Modestly, and more in some people than others. Pooling 123 studies gave a standardised mean difference of about 0.1, which is small. The benefit was clearest for efforts of two to ten minutes, in people who are recreationally rather than elite fit, and with juice or dietary nitrate rather than nitrate salt capsules.
How long before exercise should I take beetroot?
At least 150 minutes. The meta-regression found the most effective acute dose was 5 to 14.9 mmol taken two and a half hours or more before exercise. Taking it in the car park is a common and expensive mistake: the nitrate has to be converted to nitrite by oral bacteria and then reach the tissues.
Why does mouthwash ruin beetroot juice?
Because bacteria on your tongue do the first chemical step. In a crossover study, chlorhexidine mouthwash abolished the conversion of nitrate to nitrite in saliva and markedly blunted the plasma nitrite rise. The meta-analysis confirmed that practices which harm oral bacteria reduce the ergogenic effect. Skip the mouthwash on days you are using it.
Are beetroot capsules as good as the juice?
Not necessarily, and the distinction that matters is nitrate content rather than format. In the pooled analysis, nitrate salt supplements showed no significant effect while beetroot juice and high-nitrate diets did. Check the milligrams or millimoles of nitrate on the label; a capsule of beetroot powder with no stated nitrate content is a guess.
Will beetroot help me if I'm already very fit?
Less than it helps someone who is not, on the available data. Two separate correlations in the same study, one for oxygen cost and one for 3km time-trial improvement, both ran inversely against aerobic fitness. Elite athletes also showed smaller rises in plasma nitrate and nitrite from the same dose. It is one of the rare supplements where the marketing photograph is the wrong customer.
Will beetroot give me energy at my desk?
No. The nitrate literature is about the oxygen cost of exercise and blood flow, not about alertness or daytime tiredness. There is no good randomised evidence for beetroot as a general energy product, and we would rather tell you that than let you buy it for the wrong reason and conclude it does nothing.
Sources
- Larsen FJ, Weitzberg E, Lundberg JO, Ekblom B. Effects of dietary nitrate on oxygen cost during exercise. Acta Physiol (Oxf), 2007. View study
- Porcelli S, Ramaglia M, Bellistri G, Pavei G, Pugliese L, et al. Aerobic fitness affects the exercise performance responses to nitrate supplementation. Med Sci Sports Exerc, 2015. View study
- Silva KVC, Costa BD, Gomes AC, Saunders B, Mota JF. Factors that moderate the effect of nitrate ingestion on exercise performance in adults: a systematic review with meta-analyses and meta-regressions. Adv Nutr, 2022. View study
- Govoni M, Jansson EA, Weitzberg E, Lundberg JO. The increase in plasma nitrite after a dietary nitrate load is markedly attenuated by an antibacterial mouthwash. Nitric Oxide, 2008. View study
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
