Beetroot helps you last longer, not race faster

Dietary nitrate, most often taken as beetroot juice, has become one of the most popular legal performance aids among endurance athletes. The interest stems from research into its role in vascular function, since nitrate feeds into pathways that influence blood flow. Yet the trials testing it on actual performance have used very different tests, doses and populations, so it has been hard to say whether the money spent on beetroot shots buys any measurable advantage. This review set out to pool the available evidence and ask whether nitrate genuinely improves endurance exercise performance.

The authors searched six major databases from inception to October 2015 for trials comparing nitrate-only supplementation against a placebo, with a performance measure lasting at least 30 seconds. From 1,038 studies identified, 47 met the criteria, yielding 76 individual trials in healthy adults. The trials were grouped by test format, with 28 time trials, 22 time-to-exhaustion tests and 8 graded exercise tests, and the results pooled within each. The team also examined whether factors such as exercise type, dose duration, nitrate type, study quality, fitness level and the change in blood nitrite altered the outcomes.

Pooled across everything, nitrate produced a trivial effect on performance that did not reach statistical significance. The picture changed with the type of test: in time-to-exhaustion trials, nitrate produced a small to moderate and statistically significant benefit. Graded exercise tests showed a small effect in nitrate's favour that was not significant, and time trials showed essentially nothing. None of the candidate moderators, including fitness level and dose duration, significantly explained the results, and the included trials did not meaningfully disagree with each other.

The pattern here echoes a recurring theme in nitrate research: effects show up in tests of exercise capacity, which measure how long someone can keep going, rather than in tests of performance, which measure how quickly a fixed task is completed. That distinction matters because races resemble time trials, not time-to-exhaustion protocols. The review confirms nitrate does something meaningful in an exercise context while complicating the marketing claim that it makes athletes faster. The authors flag open questions around optimal dosing strategies, which populations benefit most, and the conditions under which nitrate works best.

If you take beetroot juice before races expecting a quicker finish, this pooled evidence gives limited support for that specific hope. Where nitrate does seem to help is in sustaining effort for longer before exhaustion, which may matter more in training contexts or open-ended efforts than on the clock. It is a reason to hold modest expectations rather than to bin the supplement entirely, since the capacity benefit was consistent across trials. As ever with supplements, the gap between a laboratory test and a race day result is where many promising effects quietly disappear.