Nitric oxide (NO), a gas produced naturally in the body, relaxes blood vessels and increases blood flow. Many pre-workout supplements are marketed as “NO” or “nitric oxide” boosters, with claims they can improve strength, performance, and endurance. Importantly, dietary supplements do not actually contain NO, because it’s a gas. Instead, NO supplements contain amino acids—primarily L-arginine and L-citrulline—or nitrates, all of which the body uses to make NO.

Supplements intended to increase your body’s production of NO purportedly enhance blood flow and the transport of oxygen and nutrients to the muscles. The intended end result is improved performance. Some research results suggest NO-producing supplements might improve times during distance events, delay fatigue, or both, for some people.

Foods with nitrates also are promoted to release “NO.” Dietary sources of nitrates (NO3) include beets and green, leafy vegetables; watermelon is a good source of L-citrulline. Many athletes and Warfighters now use beetroot juice as a source of NO. A number of research studies have shown that nitrates from beetroot juice might reduce exercise-induced muscle damage and extend the time before exhaustion. However, the results of these studies are mixed, and variables include type of NO producer (amino acids vs. nitrates), dose or serving size, and intensity and duration of exercise.

Because the ingredients in NO supplements can vary greatly, it isn’t possible to make a statement about their overall safety. Some dietary supplements marketed as NO boosters contain stimulants or other potentially problematic ingredients (unrelated to the NO effect) that can increase the risk of adverse reactions. However, obtaining NO from real foods such as beets, spinach, watermelon, and the like is a good option. For ratings on the safety and effectiveness of individual NO products, please visit the Natural Medicines database.

Updated 23 May 2019

ate Icon Ask the Expert Don’t see what you’re looking for? A brand-name product? A different ingredient? More details? Ask us!
References

Balsalobre-Fernández, C., Romero-Moraleda, B., Cupeiro, R., Peinado, A. B., Butragueño, J., & Benito, P. J. (2018). The effects of beetroot juice supplementation on exercise economy, rating of perceived exertion and running mechanics in elite distance runners: A double-blinded, randomized study. Plos One, 13(7), Art. e0200517. doi:10.1371/journal.pone.0200517

Burke, L. M. (2017). Practical issues in evidence-based use of performance supplements: Supplement interactions, repeated use and individual responses. Sports Medicine, 47(S1), 79–100. doi:10.1007/s40279-017-0687-1

Burleigh, M. C., Liddle, L., Monaghan, C., Muggeridge, D. J., Sculthorpe, N., Butcher, J. P., . . . Easton, C. (2018). Salivary nitrite production is elevated in individuals with a higher abundance of oral nitrate-reducing bacteria. Free Radical Biology and Medicine, 120, 80–88. doi:10.1016/j.freeradbiomed.2018.03.023

Cholewa, J., Trexler, E., Lima-Soares, F., de Araújo Pessôa, K., Sousa-Silva, R., Santos, A. M., . . . Zanchi, N. E. (2019). Effects of dietary sports supplements on metabolite accumulation, vasodilation and cellular swelling in relation to muscle hypertrophy: A focus on “secondary” physiological determinants. Nutrition, 60, 241–251. doi:10.1016/j.nut.2018.10.011

Cuenca, E., Jodra, P., Pérez-López, A., González-Rodríguez, L., Fernandes da Silva, S., Veiga-Herreros, P., & Domínguez, R. (2018). Effects of beetroot juice supplementation on performance and fatigue in a 30-s all-out sprint exercise: A randomized, double-blind cross-over study. Nutrients, 10(9), Art. 1222. doi:10.3390/nu10091222

Deane, C. S., Wilkinson, D. J., Phillips, B. E., Smith, K., Etheridge, T., & Atherton, P. J. (2017). “Nutraceuticals” in relation to human skeletal muscle and exercise. American Journal of Physiology-Endocrinology and Metabolism, 312(4), E282–E299. doi:10.1152/ajpendo.00230.2016

Domínguez, R., Cuenca, E., Maté-Muñoz, J., García-Fernández, P., Serra-Paya, N., Estevan, M., . . . Garnacho-Castaño, M. (2017). Effects of beetroot juice supplementation on cardiorespiratory endurance in athletes. A systematic review. Nutrients, 9(1), Art. 43. doi:10.3390/nu9010043

Fan, J.-L., Bourdillon, N., Meyer, P., & Kayser, B. (2018). Oral nitrate supplementation differentially modulates cerebral artery blood velocity and prefrontal tissue oxygenation during 15 km time-trial cycling in normoxia but not in hypoxia. Frontiers in Physiology, 9, Art. 869. doi:10.3389/fphys.2018.00869

Figueroa, A., Wong, A., Jaime, S. J., & Gonzales, J. U. (2017). Influence of L-citrulline and watermelon supplementation on vascular function and exercise performance. Current Opinion in Clinical Nutrition and Metabolic Care, 20(1), 92–98. doi:10.1097/mco.0000000000000340

Harty, P. S., Cottet, M. L., Malloy, J. K., & Kerksick, C. M. (2019). Nutritional and supplementation strategies to prevent and attenuate exercise-induced muscle damage: A brief review. Sports Medicine - Open, 5(1). doi:10.1186/s40798-018-0176-6

Harty, P. S., Zabriskie, H. A., Erickson, J. L., Molling, P. E., Kerksick, C. M., & Jagim, A. R. (2018). Multi-ingredient pre-workout supplements, safety implications, and performance outcomes: A brief review. Journal of the International Society of Sports Nutrition, 15(1), Art. 41. doi:10.1186/s12970-018-0247-6

Hohensinn, B., Haselgrübler, R., Müller, U., Stadlbauer, V., Lanzerstorfer, P., Lirk, G., . . . Weghuber, J. (2016). Sustaining elevated levels of nitrite in the oral cavity through consumption of nitrate-rich beetroot juice in young healthy adults reduces salivary pH. Nitric Oxide, 60, 10–15. doi:10.1016/j.niox.2016.08.006

Hon, Y. Y., Lin, E. E., Tian, X., Yang, Y., Sun, H., Swenson, E. R., . . . Machado, R. F. (2016). Increased consumption and vasodilatory effect of nitrite during exercise. American Journal of Physiology-Lung Cellular and Molecular Physiology, 310(4), L354–L364. doi:10.1152/ajplung.00081.2015

Jones, A. M. (2014). Dietary nitrate supplementation and exercise performance. Sports Medicine, 44(S1), 35–45. doi:10.1007/s40279-014-0149-y

Jonvik, K. L., Nyakayiru, J., Van Dijk, J. W., Maase, K., Ballak, S. B., Senden, J. M. G., . . . Verdijk, L. B. (2018). Repeated-sprint performance and plasma responses following beetroot juice supplementation do not differ between recreational, competitive and elite sprint athletes. European Journal of Sport Science, 18(4), 524–533. doi:10.1080/17461391.2018.1433722

Liddle, L., Burleigh, M. C., Monaghan, C., Muggeridge, D. J., Sculthorpe, N., Pedlar, C. R., . . . Easton, C. (2019). Variability in nitrate-reducing oral bacteria and nitric oxide metabolites in biological fluids following dietary nitrate administration: An assessment of the critical difference. Nitric Oxide, 83, 1–10. doi:10.1016/j.niox.2018.12.003

Ma, L., Hu, L., Feng, X., & Wang, S. (2018). Nitrate and Nitrite in Health and Disease. Aging and disease, 9(5), 938–945. doi:10.14336/ad.2017.1207

McDonagh, S. T. J., Wylie, L. J., Webster, J. M. A., Vanhatalo, A., & Jones, A. M. (2018). Influence of dietary nitrate food forms on nitrate metabolism and blood pressure in healthy normotensive adults. Nitric Oxide, 72, 66–74. doi:10.1016/j.niox.2017.12.001

McMahon, N. F., Leveritt, M. D., & Pavey, T. G. (2016). The effect of dietary nitrate supplementation on endurance exercise performance in healthy adults: A systematic review and meta-analysis. Sports Medicine, 47(4), 735–756. doi:10.1007/s40279-016-0617-7

Melik, Z., Zaletel, P., Virtic, T., & Cankar, K. (2017). L-arginine as dietary supplement for improving microvascular function. Clinical Hemorheology and Microcirculation, 65(3), 205–217. doi:10.3233/ch-16159

Poortmans, J. R., Gualano, B., & Carpentier, A. (2015). Nitrate supplementation and human exercise performance: Too much of a good thing? Current Opinion in Clinical Nutrition and Metabolic Care, 18(6), 599–604. doi:10.1097/mco.0000000000000222

Qu, X. M., Wu, Z. F., Pang, B. X., Jin, L. Y., Qin, L. Z., & Wang, S. L. (2016). From nitrate to nitric oxide. Journal of Dental Research, 95(13), 1452–1456. doi:10.1177/0022034516673019

Rodrigues-Krause, J., Krause, M., Rocha, I., Umpierre, D., & Fayh, A. (2018). Association of L-arginine supplementation with markers of endothelial function in patients with cardiovascular or metabolic disorders: A systematic review and meta-analysis. Nutrients, 11(1), Art. 15. doi:10.3390/nu11010015

Rokkedal-Lausch, T., Franch, J., Poulsen, M. K., Thomsen, L. P., Weitzberg, E., Kamavuako, E. N., . . . Larsen, R. G. (2019). Chronic high-dose beetroot juice supplementation improves time trial performance of well-trained cyclists in normoxia and hypoxia. Nitric Oxide, 85, 44–52. doi:10.1016/j.niox.2019.01.011

Shannon, O. M., McGawley, K., Nybäck, L., Duckworth, L., Barlow, M. J., Woods, D., . . . O’Hara, J. P. (2017). “Beet-ing” the mountain: A review of the physiological and performance effects of dietary nitrate supplementation at simulated and terrestrial altitude. Sports Medicine, 47(11), 2155–2169. doi:10.1007/s40279-017-0744-9

Suzuki, I., Sakuraba, K., Horiike, T., Kishi, T., Yabe, J., Suzuki, T., . . . Suzuki, Y. (2019). A combination of oral L-citrulline and L-arginine improved 10-min full-power cycling test performance in male collegiate soccer players: A randomized crossover trial. European Journal of Applied Physiology, 119(5), 1075–1084. doi:10.1007/s00421-019-04097-7

Thomas, B., Smallwood, S., Cutler, C., & Bescos, R. (2019). The oral nitrate-reducing capacity correlates with peak power output and peak oxygen uptake in healthy humans. Nitric Oxide, 87, 43–51. doi:10.1016/j.niox.2019.03.001

Thompson, C., Wylie, L. J., Blackwell, J. R., Fulford, J., Black, M. I., Kelly, J., . . . Jones, A. M. (2017). Influence of dietary nitrate supplementation on physiological and muscle metabolic adaptations to sprint interval training. Journal of Applied Physiology, 122(3), 642–652. doi:10.1152/japplphysiol.00909.2016

Vanhatalo, A., Blackwell, J. R., L’Heureux, J. E., Williams, D. W., Smith, A., van der Giezen, M., . . . Jones, A. M. (2018). Nitrate-responsive oral microbiome modulates nitric oxide homeostasis and blood pressure in humans. Free Radical Biology and Medicine, 124, 21–30. doi:10.1016/j.freeradbiomed.2018.05.078

Wickham, K. A., McCarthy, D. G., Pereira, J. M., Cervone, D. T., Verdijk, L. B., van Loon, L. J. C., . . . Spriet, L. L. (2019). No effect of beetroot juice supplementation on exercise economy and performance in recreationally active females despite increased torque production. Physiological Reports, 7(2), Art. e13982. doi:10.14814/phy2.13982