In 2009, researchers at the University of Exeter conducted an experiment. Nine healthy, active men drank 500 ml of beetroot juice every day for six days — or an identical-looking juice without nitrate. They then cycled to exhaustion.
The nitrate group lasted 16% longer. Their hearts did not beat faster. Their muscles were not stronger. They simply used less oxygen to produce the same effort.
That is the effect this article is about — and it has been confirmed time and again in hundreds of studies over the past 15 years.
Key takeaways
- Dietary nitrate from beetroot gives the body the building blocks for nitric oxide — NO for short, or nitric oxide in English. NO widens blood vessels and improves how much oxygen reaches the muscles during exercise.
- The effect is not a stimulant. No racing heart, no adrenaline. It is an improvement in efficiency: the same effort with less oxygen used.
- Studies consistently show that endurance athletes last longer, have a lower heart rate at the same speed, and improve time-trial performance by 1–3% [1], [2], [3].
- The effect is strongest in recreational endurance athletes. It is smaller in professionals, whose vascular systems are already highly optimised.
- Effective doses used in studies: 200–800 mg of nitrate per day, taken 2–3 hours before exercise.
Why beetroot is no ordinary superfood
Beetroot contains many nutrients — folate, potassium and fibre. What sets it apart from almost every other vegetable is its exceptionally high nitrate content. Nitrate is the active ingredient that matters in this context; everything else is secondary.
Bacteria on the tongue convert dietary nitrate into nitrite in the mouth. In the stomach and tissues, this is converted into NO — nitric oxide. NO signals blood vessels to relax and widen. More blood flows through. The muscles receive more oxygen — and use it more efficiently.
That may sound like a small effect. But in a sport where seconds decide the standings, being “2% more efficient” is no small thing. It can be the difference between third place and a podium finish.
What the studies show in practice: the numbers
More than two dozen controlled studies have examined dietary nitrate in endurance athletes. The results are not identical, but the direction is consistent. Here are the key findings in summary:
- 16% longer to exhaustion during high-intensity exercise — after six days of daily intake of around 400 mg of nitrate [1]
- 5% less oxygen consumption during moderate exercise — the same output with less effort [1], [2]
- 2.7% faster 10 km time trial on the bike — under real race conditions, not just in laboratory tests [3]
- Lower heart rate at the same speed — less strain on the heart at the same pace
- Consistent effects across 20 meta-analyses involving more than 2,600 participants: regular intake from around 370 mg per day is associated with reliable improvements in endurance [4]
What these numbers mean: in a 20-minute 10 km time trial, 2.7% is around 30 seconds. For a recreational cyclist, that is a noticeable improvement. For someone who races, it can be decisive. And the 16% endurance effect is not a laboratory artefact — it was demonstrated against a controlled placebo juice that looked and tasted identical.
It is important to understand that the effect comes exclusively from nitrate, not from other compounds in beetroot. Studies using isolated nitrate without any vegetables show the same endurance effect [2]. Betalains, polyphenols, colour — none of these are relevant to this mechanism.
What you feel — and why it is not a quick kick
Dietary nitrate does not work like caffeine. No tingling, no faster heartbeat, no “here we go” feeling. If that is what you expect, you may notice nothing after your first dose.
What happens instead is that your muscles work more efficiently. The same speed takes less effort. After training with beetroot nitrate for the first time, people often only notice afterwards that a tough session felt “somehow easier” — or that their heart rate was lower than usual at their normal pace. That is not a weak effect. It is exactly the effect measured in studies — one that builds and stabilises over several weeks of daily use.
Who is most likely to benefit — and what that means for you
Endurance athletes: The evidence is strongest here: runners, cyclists and triathletes, particularly recreational and moderately trained athletes. Studies show lower oxygen consumption at the same speed, a higher threshold for exhaustion and better time-trial results. The longer the effort, the more relevant the effect may be, because dietary nitrate works particularly well when oxygen is in short supply.
People over 40: The body’s own NO production in the blood vessel walls measurably declines with age. This contributes to stiffer blood vessels, higher blood pressure and slower recovery. Dietary nitrate follows a different pathway and compensates for this, regardless of how well or poorly the body’s own production is still working. Studies also show measurable increases in blood markers relevant to NO in older adults, alongside improved blood flow and blood pressure effects [4]. Read more in our article on nitric oxide and the two pathways to NO.
Elite athletes: The effect is smaller because their vascular systems are already highly optimised. It is not absent, but expectations should be realistic.
Timing and dose: how to use the effect well
Take it 2–3 hours beforehand. Not just before training. The nitrate pathway needs this time to reach its peak. If you take it immediately before exercise, you will still be in the absorption phase — the strongest effect will come too late.
Every day, not sporadically. Single doses can work, but taking it over several days is much more reliable. If you want to optimise before an important event, take it daily for 5–7 days beforehand to build stable levels. The same principle applies day to day: with daily use, you may notice a more consistent effect after one or two weeks than with irregular use.
At least 370 mg of nitrate per day. Below this threshold, large reviews of the evidence often no longer find clear effects [4]. This is the most common reason retail beetroot products disappoint: not because the mechanism does not work, but because the dose is too low and usually is not stated on the label.
Why some people feel nothing — and what may help
People do not all respond to dietary nitrate in the same way. There are several reasons: the make-up of their oral bacteria (responsible for the first conversion step), their starting levels, timing and dose. If you notice no difference after 10–14 days of daily use, check whether something is blocking the effect — mouthwash, taking it too early or too low a dose. The article on common mistakes in the process explains more about NO production and what can undermine it.
Overall, the evidence is clear: the effects are real, replicated and well documented. The size of the effect varies from person to person, but the direction is upward for almost everyone.
Frequently asked questions
- Does beetroot extract work as well as beetroot juice for sport?
- Yes — if the nitrate content is comparable. Most studies used juice because its nitrate content could be measured before the study. The mechanism depends on nitrate, not the form. A standardised extract that states the nitrate content in mg can provide the same effect as an equivalent amount of juice, and is more reliable because retail juice varies considerably.
- When should I take it before training?
- 2–3 hours before training. The nitrate pathway needs this time to reach its peak. If you take it immediately before training, you will still be in the absorption phase. For competitions, studies also recommend a 5–7-day loading period to stabilise the effect.
- Can NO support help with strength training too?
- Yes, but the effect differs from endurance exercise. In strength training, the main potential advantage is fatigue resistance: more repetitions before muscular failure and shorter recovery between sets. The oxygen-efficiency effect that matters most in endurance exercise plays a smaller role in short strength exercises. L-citrulline is particularly relevant for strength training because it supports the faster arginine pathway.
- Will I feel a difference after the first dose?
- Some people do — particularly with 400 mg or more, taken 2–3 hours before training. Many notice a difference only after several days of consistent use. The effect builds with daily use. Not seeing a clear result after a single dose does not disprove the effect.
The doses used in the studies
The nitrate amounts used in these studies ranged from 200 to 800 mg per day, from beetroot juice or standardised extract — always with a known, measured nitrate content. That is the key point: researchers knew how much nitrate they were giving. Retail products without an amount in mg do not offer that certainty.
Circ. Essential provides daily 200 mg of standardised dietary nitrate — the lower end of the doses used in research, for consistent daily use.
Circ. Performance provides 400 mg of standardised dietary nitrate plus 3 g of pure L-citrulline — for training days when you want both NO pathways active at once. 400 mg is exactly in the middle of the study doses that show the strongest endurance effect.
→ Nitric oxide: the two pathways explained
→ Beetroot powder: what really matters on the label
→ 7 mistakes that undermine your NO production
Scientific references
- Bailey, S.J. et al. (2009). Dietary nitrate supplementation reduces the O₂ cost of low-intensity exercise and enhances tolerance to high-intensity exercise in humans. Journal of Applied Physiology, 107(4), 1144-1155. Randomised controlled trial, n=9; 500 ml of beetroot juice (~400 mg nitrate) for 6 days vs nitrate-free placebo; 5% lower oxygen consumption during submaximal exercise and 16% longer time to exhaustion.
- Larsen, F.J. et al. (2007). Effects of dietary nitrate on oxygen cost during exercise. Acta Physiologica, 191(1), 59-66. Sodium nitrate supplementation (not beetroot); reduced oxygen consumption during submaximal cycling; evidence that the effect comes from nitrate, not other beetroot compounds.
- Cermak, N.M. et al. (2012). Nitrate supplementation's improvement of 10-km time-trial performance in trained cyclists. International Journal of Sport Nutrition and Exercise Metabolism, 22(1), 64-71. Beetroot concentrate as a supplement; 10 km cycling time trial; average time 2.7% faster than with placebo.
- Poon, E.T.-C. et al. (2025). Effects of dietary nitrate supplementation on exercise performance: an umbrella review of 20 meta-analyses. Sports Medicine. Review of 20 meta-analyses, n=2,672; chronic nitrate intake from ~370 mg per day showed consistent endurance effects (SMD ~0.33); the effect was greater in recreational athletes than in elite athletes; single doses were less reliable than taking it over several days.
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