Nitric Oxide Benefits: 5 Claims Tested, and Who Actually Benefited
Quick Answer: Nitric oxide relaxes blood vessels, and raising it, usually with dietary nitrate from beetroot or leafy greens, has measurable benefits, but mostly for particular people. For exercise, an analysis of 80 trials found a real but small performance boost in recreationally active young men, and no effect in well-trained endurance athletes or in the handful of women-only studies. In people with blocked leg arteries, beetroot juice let them walk 18% longer before pain. For erectile dysfunction, arginine supplements improved mild to moderate ED across 10 trials. For blood pressure, nitrate lowers it in healthy people but did little in people with hypertension. And if you buy a “nitric oxide booster,” citrulline raised blood arginine more than arginine itself did. Our product pick for this topic, CircO2, is in the box near the end of this page.
Nitric oxide is a gas your blood vessels make to widen themselves. It is short-lived, so supplements cannot contain it; they contain raw materials, either nitrate (beetroot, leafy greens) or the amino acids arginine and citrulline. This page takes five common claims about nitric oxide benefits and checks each against human trials, with attention to who in those trials actually improved. For the food sources, see foods high in nitric oxide; for the whole picture, how to increase nitric oxide naturally.
The scoreboard
| Claimed benefit | What trials found | Who benefited |
|---|---|---|
| Exercise performance | Small improvement across 80 trials (effect size 0.17) | Recreationally active young men; not well-trained athletes |
| Lower blood pressure | Lower systolic pressure in healthy people; no significant change in hypertension | Healthy adults |
| Circulation in the legs | 18% longer walking before pain, 17% longer peak walking | 8 people with peripheral artery disease |
| Erectile function | Improved versus placebo in 10 trials (odds ratio 3.37) | Men with mild to moderate ED, on arginine |
| Raising NO with a supplement | Citrulline raised blood arginine more than arginine did | Healthy volunteers |
1. Exercise performance: the fitter you are, the less it does
This is the most studied claim. A 2020 meta-analysis in Medicine & Science in Sports & Exercise pooled 80 randomized, placebo-controlled crossover studies in young, healthy adults. Nitrate improved performance compared with placebo, but the effect was “objectively small” (d = 0.174). Breaking the results down:
Beet powders and capsules rarely state their nitrate: of 190 beet products in the NIH label database, only three gave enough to calculate it. See beet root powder benefits.
- Recreationally active men: a clear effect, across different types of exercise and dosing.
- Well-trained endurance athletes (VO2 max of 65 mL/kg/min or more, 26 studies): no effect (d = 0.021, P = 0.745).
- Women-only studies (6 studies): no significant effect, though there were too few to be sure.
An Italian study explains why. When people of different fitness levels took nitrate, the improvement in a 3-km time trial was inversely correlated with fitness (r = 0.76): the less fit the person, the bigger the gain. Fitter people also showed a smaller rise in blood nitrate and nitrite after the same dose. The authors concluded that the regimen needed to help elite athletes “is different from that of low-fit subjects.”
If you are looking for a supplement here, CircO2 is a nitric oxide lozenge that dissolves on the tongue (affiliate link; details in our pick below).
2. Blood pressure: healthy people, not hypertension
Nitrate lowers blood pressure quickly in healthy volunteers. In people who already have high blood pressure, the picture is weaker: a 2023 meta-analysis found no significant drop in systolic pressure in hypertensive people, and a five-week trial of 243 adults with raised blood pressure found leafy greens rich in nitrate did not lower it. The details are in our foods high in nitric oxide page. Antiseptic mouthwash also blocks part of the effect, as we explain in does mouthwash destroy nitric oxide.
3. Circulation in the legs: a small trial with a clear signal
People with peripheral artery disease (PAD) have narrowed leg arteries and get calf pain when they walk. In a Duke University crossover study, eight people with PAD drank 500 mL of beetroot juice or a placebo before a treadmill test. After beetroot juice they walked 18% longer before pain started (215 vs 183 seconds) and had a 17% longer peak walking time (533 vs 467 seconds). Their calf muscles also extracted less oxygen during exercise, consistent with better blood supply. Eight people is a very small trial, but it is one of the few to test nitrate in people with a circulation problem rather than in athletes.
4. Erectile function: arginine, for mild to moderate ED
Erections depend on nitric oxide relaxing blood vessels, which is why “nitric oxide for ED” is a common search. A 2019 meta-analysis in the Journal of Sexual Medicine pooled 10 randomized trials covering 540 men. Arginine at 1,500 to 5,000 mg a day improved ED compared with placebo or no treatment (odds ratio 3.37), with better scores for erectile function, orgasmic function and satisfaction, but not for sexual desire. Side effects were more common on arginine (8.3% vs 2.3%), none severe. The authors concluded that arginine “can be recommended to patients with mild to moderate ED,” and noted that doses and durations varied between studies.
5. Arginine or citrulline: the supplement question
Most “nitric oxide booster” pills contain arginine, citrulline or beetroot extract. A German study compared oral arginine and citrulline head-to-head in healthy volunteers. Citrulline raised blood arginine more effectively than arginine itself, in a dose-dependent way, and at 3 g twice a day it increased markers of nitric oxide signalling. Neither supplement improved blood-vessel dilation over baseline, though people whose arginine balance improved most showed the most improvement. The practical reading: if you want to raise arginine, citrulline is the more efficient route; whether that translates into a felt benefit is less certain.
Women have specific questions about nitric oxide supplements, which we cover in nitric oxide for women.
Frequently Asked Questions
What are the benefits of nitric oxide?
In trials: a small boost to exercise performance in recreationally active people, lower blood pressure in healthy adults, longer pain-free walking in people with blocked leg arteries, and, with arginine, improvement in mild to moderate erectile dysfunction.
Does nitric oxide help athletes?
Mainly recreational ones. In a meta-analysis of 80 trials, nitrate had no effect in well-trained endurance athletes with a VO2 max of 65 mL/kg/min or more.
Is nitric oxide good for erectile dysfunction?
Arginine, which the body uses to make nitric oxide, improved mild to moderate ED in a meta-analysis of 10 trials with 540 men, at 1,500 to 5,000 mg a day.
Is citrulline or arginine better?
Citrulline raised blood arginine more effectively than arginine itself in a head-to-head study of healthy volunteers.
Does nitric oxide lower blood pressure?
Nitrate lowers systolic pressure in healthy people. In people with hypertension, a 2023 meta-analysis found no significant change, so it is not a substitute for treatment.
Are nitric oxide supplements safe?
In the ED meta-analysis, side effects were more common on arginine than placebo (8.3% vs 2.3%) but none were severe. If you take medication for blood pressure or erectile dysfunction, talk to your doctor before adding a nitric oxide supplement.
The Bottom Line
Nitric oxide benefits are real but uneven. Nitrate helps recreational exercisers a little and well-trained athletes not at all; it lowers blood pressure in healthy people more than in people with hypertension; it helped people with leg artery disease walk further in one small trial; and arginine helped mild to moderate ED across 10 trials. If you try a supplement, citrulline raises arginine more efficiently than arginine does.
🔎 Our researched pick: CircO2 is a nitric oxide lozenge that dissolves on the tongue, the step where dietary nitrate is first converted. Our CircO2 review covers what is in it.
Affiliate link — if you buy through it we may earn a commission at no extra cost to you.
Sources
- Senefeld JW, Wiggins CC, Regimbal RJ, et al. Ergogenic Effect of Nitrate Supplementation: A Systematic Review and Meta-analysis. Med Sci Sports Exerc, 2020;52(10):2250-2261. PMID 32936597. 80 studies; d = 0.174 overall; women-only n = 6, d = 0.116 (P = 0.347); well-trained endurance athletes (≥65 mL/kg/min) n = 26, d = 0.021 (P = 0.745); “objectively small”. Checked 6 October 2026.
- Porcelli S, Ramaglia M, Bellistri G, et al. Aerobic Fitness Affects the Exercise Performance Responses to Nitrate Supplementation. Med Sci Sports Exerc, 2015;47(8):1643-1651. PMID 25412295. Inverse correlation between aerobic fitness and 3-km time-trial improvement (r = 0.76); smaller plasma nitrate and nitrite rise in higher-fit subjects. Checked 6 October 2026.
- Kenjale AA, Ham KL, Stabler T, et al. Dietary nitrate supplementation enhances exercise performance in peripheral arterial disease. J Appl Physiol, 2011;110(6):1582-1591. PMID 21454745. n = 8, 500 mL beetroot juice vs placebo; claudication onset 215 vs 183 s (18%); peak walking 533 vs 467 s (17%). Checked 6 October 2026.
- Rhim HC, Kim MS, Park YJ, et al. The Potential Role of Arginine Supplements on Erectile Dysfunction: A Systemic Review and Meta-Analysis. J Sex Med, 2019;16(2):223-234. PMID 30770070. 10 RCTs, 540 men; 1,500-5,000 mg; OR 3.37 (1.29-8.77); adverse effects 8.3% vs 2.3%, none severe. Checked 6 October 2026.
- Schwedhelm E, Maas R, Freese R, et al. Pharmacokinetic and pharmacodynamic properties of oral L-citrulline and L-arginine: impact on nitric oxide metabolism. Br J Clin Pharmacol, 2008;65(1):51-59. PMID 17662090. Citrulline increased plasma arginine AUC and Cmax more effectively than arginine; 3 g twice daily raised urinary nitrate and cGMP; no treatment improved FMD over baseline. Checked 6 October 2026.
- Zhang Y, Zhang H, An W, Li D, Qin L. Regulatory effect of dietary nitrate on blood pressure: a meta-analysis of randomized controlled trials. Food Funct, 2023;14(4):1839-1850. PMID 36740972. Healthy SBP -2.42 mm Hg; hypertensive SBP -0.82 mm Hg (P = 0.35). Checked 6 October 2026.
- Sundqvist ML, Larsen FJ, Carlström M, et al. A randomized clinical trial of the effects of leafy green vegetables and inorganic nitrate on blood pressure. Am J Clin Nutr, 2020;111(4):749-756. PMID 32091599. 243 adults with elevated BP, 5 weeks; no significant difference. Checked 6 October 2026.
Featured photo: jogging couple, by Ed Yourdon, Wikimedia Commons, CC BY-SA 2.0.
