TL;DR

  • Nitric oxide (NO) relaxes arteries, lowering blood pressure and improving blood flow.
  • Arginine and citrulline are key supplements that raise NO levels.
  • Best evidence: blood pressure support, circulation, exercise performance, and erectile dysfunction.
  • Citrulline often works better than arginine, but a combination may be strongest.

What Is Nitric Oxide (NO)?

Nitric oxide is a signaling molecule made by the cells lining your blood vessels. Its main role is relaxing the arteries (vasodilation). This helps:

  • Lower blood pressure
  • Improve circulation
  • Deliver oxygen and nutrients to tissues

When NO is low, blood pressure often rises. When NO is boosted, vascular tone decreases.

Nitric Oxide and Exercise Performance

Because NO improves circulation, it has been studied in athletes. Some studies show small but meaningful performance gains, especially for trained or elite athletes. The benefits are subtle but can matter in high-level competition.

Arginine: The Direct Precursor

  • What it does: Arginine is converted directly into NO by nitric oxide synthase (NOS).
  • Uses studied: Blood pressure, exercise performance, circulation in the legs (intermittent claudication), and erectile dysfunction.
  • Limitation: Some of it is broken down in the gut before reaching the bloodstream.

Citrulline: Often More Effective

  • What it does: Citrulline turns into arginine in the body.
  • Advantage: It bypasses breakdown in the intestines, so more reaches the blood.
  • Result: Often raises arginine levels more efficiently than arginine itself.
  • Best use: Citrulline and arginine together can give the strongest bump in NO.

(Internal link: Citrulline vs. arginine: which is better?)

Who May Benefit

  • Adults with high or borderline blood pressure (with clinician guidance)
  • Athletes seeking small performance gains
  • People with intermittent claudication
  • Men with erectile dysfunction (adjunct, not replacement therapy)

How to Support NO Naturally

  • Foods: Beets, leafy greens, garlic, citrus, pomegranate
  • Exercise: Boosts natural endothelial function
  • Supplements:
    • Arginine
    • Citrulline
    • Combo of both (often most effective)
  • Timing: Pre-workout for performance, or daily for heart health

Safety & Interactions

  • Usually well tolerated, but stomach upset can occur.
  • Talk to your clinician if you take:
    • Blood pressure meds
    • Nitrates
    • PDE-5 inhibitors (like sildenafil)
    • Or if you have heart/kidney issues, are pregnant, or breastfeeding.

FAQs

Does nitric oxide lower blood pressure?
Yes—boosting NO relaxes arteries, helping reduce resistance and support healthy blood pressure.

Is arginine or citrulline better?
Citrulline often raises arginine levels more efficiently. A combination may work best.

Can NO supplements help exercise?
Yes, but effects are usually small. Best studied in trained or elite athletes.

What about erectile dysfunction?
Arginine-based NO support can help by improving circulation, but it’s usually part of a bigger plan—not a stand-alone treatment.

Disclaimer: This article is for educational purposes only and not medical advice. Always consult your healthcare provider before starting supplements, especially if you take medication or have a medical condition.

Research Supporting the Use of Arginine and Citruline

  1. Circulation. 1995 Aug 1;92(3):320-6. Contribution of nitric oxide to metabolic coronary vasodilation in the human heart
  2. Platelets. 2012;23(1):26-35. Nitric oxide and peroxynitrite platelet levels in gestational hypertension and preeclampsia
  3. J Hypertens. 1993 Dec;11(12):1375-80 Inhibition of nitric oxide synthesis increases blood pressure in healthy humans
  4. J Strength Cond Res. 2016 Dec;30(12):3520-3524 Ingestion of a Nitric Oxide Enhancing Supplement Improves Resistance Exercise Performance
  5. J Am Heart Assoc. 2020 Mar 3;9(5):e014923 New Nutraceutical Combination Reduces Blood Pressure and Improves Exercise Capacity in Hypertensive Patients Via a Nitric Oxide-Dependent Mechanism
  6. Sports Med. 2019 May;49(5):707-718 Acute Effects of Citrulline Supplementation on High-Intensity Strength and Power Performance: A Systematic Review and Meta-AnalysisEur J Clin Nutr 2010 Feb;64(2):221-3 Vitamin B6 deficiency and anemia in pregnancy
  7. Clin Sci (Lond). 1995 Feb;88(2):135-9. L-arginine increases exhaled nitric oxide in normal human subjects
  8. Hypertens Pregnancy. 2007;26(1):121-30. L-arginine supplementation in patients with gestational hypertension: a pilot study
  9. Clin Exp Pharmacol Physiol. 2009 Mar;36(3):249-55. Role of L-arginine in nitric oxide production in health and hypertension
  10. Clin Sci (Lond). 2015 Jan;128(1):57-67. Arginine infusion in patients with septic shock increases nitric oxide production without haemodynamic instability
  11. Biochem J. 1998 Nov 15;336 ( Pt 1)(Pt 1):1-17. Arginine Metabolism: Nitric Oxide and Beyond
  12. Free Radic Res. 2019 Mar;53(3):281-292 L-Arginine and Tetrahydrobiopterin Supported Nitric Oxide Production Is Crucial for the Microbicidal Activity of Neutrophils
  13. Am J Clin Nutr. 2009 Jan;89(1):77-84. Increase in Fasting Vascular Endothelial Function After Short-Term Oral L-arginine Is Effective When Baseline Flow-Mediated Dilation Is Low: A Meta-Analysis of Randomized Controlled Trials
  14. Proc Natl Acad Sci U S A. 2017 Feb 14;114(7):1714-1719. Sirtuin1-regulated Lysine Acetylation of p66Shc Governs Diabetes-Induced Vascular Oxidative Stress and Endothelial Dysfunction
  15. Hypertension. 2019 Apr;73(4):839-848. Dietary Nitrate Reduces Blood Pressure in Rats With Angiotensin II-Induced Hypertension via Mechanisms That Involve Reduction of Sympathetic Hyperactivity
  16. Clin Sci (Lond). 2019 Oct 30;133(20):2061-2067. Impaired L-Arginine-Nitric Oxide Pathway Contributes to the Pathogenesis of Resistant Hypertension
  17. Hypertension. 2012 Apr;59(4):825-32. Nitric Oxide Production and Endothelium-Dependent Vasorelaxation Ameliorated by N1-methylnicotinamide in Human Blood Vessels
  18. J Clin Hypertens (Greenwich). 2014 Jul;16(7):524-9 Acute Effects of an Oral Nitric Oxide Supplement on Blood Pressure, Endothelial Function, and Vascular Compliance in Hypertensive Patients
  19. Aging (Albany NY). 2019 May 29;11(10):3315-3332. Effect of Chronic Nitrate and Citrulline Supplementation on Vascular Function and Exercise Performance in Older Individuals
  20. J Am Coll Cardiol. 1998 Nov;32(5):1336-44. Restoring Vascular Nitric Oxide Formation by L-arginine Improves the Symptoms of Intermittent Claudication in Patients With Peripheral Arterial Occlusive Disease
  21. Sports Medicine volume 42, pages99–117(2012) The Effect of Nitric-Oxide-Related Supplements on Human Performance
  22. Future Sci OA. 2015 Aug; 1(1): FSO53. Development and therapeutic applications of nitric oxide releasing materials to treat erectile dysfunction
  23. J Sex Marital Ther. 2003 May-Jun;29(3):207-13 Treatment of erectile dysfunction with pycnogenol and L-arginine
  24. Andrologia. 2020 Aug;52(7):e13640. Comparison of the clinical efficacy of daily use of L-arginine, tadalafil and combined L-arginine with tadalafil in the treatment of elderly patients with erectile dysfunction
  25. J Sex Med. 2019 Feb;16(2):223-234 The Potential Role of Arginine Supplements on Erectile Dysfunction: A Systemic Review and Meta-Analysis
  26. Br J Clin Pharmacol. 2008 Jan;65(1):51-9.
  27. Biosci Biotechnol Biochem. 2017 Feb;81(2):372-375. The effects on plasma L-arginine levels of combined oral L-citrulline and L-arginine supplementation in healthy males
  28. Biochem Biophys Res Commun. 2014 Nov 7;454(1):53-7. Oral supplementation with a combination of L-citrulline and L-arginine rapidly increases plasma L-arginine concentration and enhances NO bioavailability
  29. Biosci Biotechnol Biochem. 2017 Feb;81(2):372-375. The effects on plasma L-arginine levels of combined oral L-citrulline and L-arginine supplementation in healthy males