Beetroot juice and nitrates: what they actually do, the dose, and whether it's worth it

What beetroot juice nitrates actually do for training, the exact dose in milligrams, when to take it, and who gets little out of it.

Beetroot juice is one of the few supplements where the effect genuinely shows up in measurements — but it is smaller than the marketing suggests and it does not work for everyone. The active ingredient is not beetroot but nitrate, the dose is quite specific, and a couple of ordinary daily habits can wipe the effect out completely. Here are the numbers and a workable protocol.

What actually happens in the body

Dietary nitrate is converted to nitrite by bacteria living on the back of your tongue. Nitrite then becomes nitric oxide (NO) in the stomach and bloodstream — a molecule that widens blood vessels and changes how efficiently muscle cells use oxygen.

The practical consequence: at the same pace you use roughly 3–5% less oxygen. Same work, lower cost. The effect is stronger in fast-twitch (type II) fibres and under low oxygen conditions, which means high intensities and the back end of hard sets.

How big is the effect

Time to exhaustion in the lab: +4% to +25%. Impressive-sounding, but that test format always exaggerates.
Efforts of 4 to 30 minutes (races, time trials): 1–3% faster. On a 22-minute 5K that is 13 to 40 seconds.
Repeated sprints (6–10 x 15–30 s): 2–5% more average power in the final reps.
Gym strength: some studies show 1–2 extra reps in a set to failure at 60–70% 1RM. The findings are inconsistent and I would not build a plan on them.
Blood pressure: 3–5 mmHg lower systolic and 1–2 mmHg lower diastolic in people with elevated readings.

Who gets the least: well-trained endurance athletes with a VO2max above 60–65 ml/kg/min. Their bodies already produce plenty of NO and there is almost no room to improve. Who gets the most: recreational trainees, people training at altitude, and repeated-sprint sports like football, basketball and combat sports.

The dose, specifically

The effective dose is 6.4 to 12.8 mmol of nitrate, roughly 400 to 800 mg. Below 5 mmol (about 310 mg) most studies find nothing, and going above 12.8 mmol adds nothing either.

Acute: one dose of 400–800 mg of nitrate, 2 to 3 hours before the effort. Blood nitrite peaks around 2–2.5 hours after intake.
Loading: the same daily dose for 3 to 7 consecutive days, plus a final dose 2–3 hours before competition. This is the more reliable version and the one I would use when the day matters.
Do not stack it: 16 mmol is not better than 8 mmol, it just raises the odds of stomach trouble.

Food or concentrate

Concentrated 60–70 ml shot: typically 400 mg of nitrate per bottle, with the amount declared. Easiest way to dose precisely.
Regular beetroot juice: you need 250–500 ml to reach 400 mg, but nitrate content varies three- to fivefold with soil, variety and season.
Cooked beetroot: 200–300 g. Boiling in a lot of water leaches part of the nitrate out.
Rocket (arugula): 60–100 g can deliver 300–450 mg. The most concentrated everyday source there is.
Spinach: 150–250 g. Lettuce, chard and celery are solid too.

Your muscles do not care whether the nitrate came from beetroot or rocket. Beetroot is simply easier to dose.

Three mistakes that cancel the effect

Antibacterial mouthwash. It kills the tongue bacteria that convert nitrate to nitrite and removes 60–100% of the effect. Skip it on any day when the nitrate matters.
Spitting during the first 1–2 hours (chewing gum, tobacco). You are discarding a step of the process that happens in your mouth.
Taking it 20 minutes before training. Far too early in the curve — nitrite is only starting to rise. This is the most common error.

Side effects

Red urine and stool show up in roughly 10–15% of people and are harmless. Cramping and loose stools are more common with large volumes of regular juice (400 ml and up) than with concentrate. Test everything in training at least twice before you try it on a competition day.

When to see a doctor

If you take prescription nitrates (nitroglycerin, isosorbide) or erectile dysfunction medication — the combination can drop blood pressure sharply.
If you are on blood pressure medication, or already run low and get dizzy standing up.
Kidney disease or a history of kidney stones — beetroot is high in oxalate.
Chest pain, unusual breathlessness or fainting during effort. That is not a supplement question, it is an examination question.
Infants under 6 months should not be given nitrate-rich juices at all.

How to test whether it works for you

Pick a test you can repeat under the same conditions: 2000 m on a rowing ergometer, a 5K run, or a 20-minute cycling power test. Run three measurements over three weeks — one without nitrate, one after 4 days of loading, one without again. A difference under 1% is measurement noise. If you do not see at least 1.5–2%, it is not worth the money or the hassle.

The short version

The dose is 400–800 mg of nitrate (6.4–12.8 mmol), taken 2–3 hours before the effort; more does not help.
Loading for 3–7 days with a final dose 2–3 hours out is the most reliable approach.
Realistic gain is 1–3% on efforts of 4 to 30 minutes — often nothing at all in well-trained athletes.
Antibacterial mouthwash destroys almost the entire effect; drop it that day.
Rocket, spinach and cooked beetroot do the same job as a concentrate, just with a less precise dose.