Review Articles
Nitric Oxide Supplements (Bodybuilding and Athletic Performance) Review Article
 

Initial Posting: 11/11/11 

Nitric Oxide Supplements Review Sections: Jump to a section by clicking on its name.
What Is Nitric Oxide?
Nitric oxide has been generating a lot of buzz lately in both research labs and weight rooms. Not to be confused with nitrous oxide or "laughing gas," nitric oxide (NO) is a different gas that plays important roles throughout the body. Among other things, it's a vasodilator that tells the blood vessels to relax, a crucial step for encouraging blood flow. Recent research suggests that regular exercise may help bolster the supply of NO, which might be a large reason why workouts improve circulation and lower the risk of heart disease.

What Are Nitric Oxide Supplements?
Many people in the weight-training crowd see NO as a natural shortcut to greater strength and bigger muscles. The idea is that anything that boosts blood flow to the muscles will also boost performance and results. People interested in a quick NO fix have turned to dietary supplements that claim to increase the supply of the gas NO. Most of these products contain L-arginine, an amino acid that helps fuel the enzyme (NO synthase) that produces NO. While other ingredients may be included in NO supplements, there is little to no research supporting their effect the production of NO.
 
NO supplements include products like naNO Vapor, Nitric Stack, Nitrix, NO Fury, and NOX-3. Dramatic claims made on some NO products or websites selling them include:
  • Harnesses the power of nitric oxide to get you incredibly pumped beyond belief.
  • Contains a unique blend of arginine that will deliver massive muscle pumps and extreme muscle hardness and fullness after your very first dose!
  • Amplified nitric oxide release that leads to muscle growth activation.
  • Transforms the 2-hour or less window of "pumped perfection" into a physique-altering phenomenon that lasts the entire day.

Do Nitric Oxide Supplements Really Work?
There is no doubt that nitric oxide plays a vital role in circulation. But even though some bodybuilders swear by the results of "nitric oxide" supplements, it's not clear that taking large doses of L-arginine or other amino acids orally significantly increases production of nitric oxide in everyone.

The research studies published on nitric oxide supplements in athletes so far haven't been promising. A 2009 study of well-trained male athletes found that giving 6 grams of L-arginine supplementation for three days raised their serum arginine levels but had no effect on nitric oxide production or performance of intermittent anaerobic exercise (Liu, J Nutr Biochem 2009). In that study, nitric oxide production did increase during exercise, but no more so with L-arginine than placebo. A 2011 study of eight healthy young men published in the Journal of Nutrition found no evidence that a beverage containing 10 grams of L-arginine improved blood flow to the muscles or did anything to speed muscle buildup after weight lifting (Tang, J Nutr 2010).

A 2010 study including three different commercially available "nitric oxide" supplements published in the Journal of the International Society of Sports Nutrition found that none of the supplements (powders given in a mixture with water 30 minutes prior to exercise) significantly improved weight-lifting performance or muscle "pump" (the feeling that muscles were bigger, fuller, and harder) in resistance-trained men (Bloomer, J Int Soc Sports Nutr 2010). The supplements also did not raise biological indicators of nitric oxide in the blood or oxygen in muscles. The products each listed L-arginine within a proprietary blend of other ingredients but did not specify the specific amount of L-arginine, like many NO supplements on the market.

Nitric oxide supplements may not be the answer for big muscles or for elite athletes, but there's still some hope that they can improve exercise performance in certain individuals. A 2010 study by researchers at UCLA published in the Journal of the International Society of Sports Nutrition found that a dose of Niteworks (from Herbalife), a supplement containing 5.2 grams of a blend of L-arginine and L- citruline, increased the time that older male cyclists (aged 50 to 73 years) could work out before reaching the anaerobic threshold, the point at which lactic acid starts building up in muscles (Chen, J Int Sports Nutri, 2010). Niteworks includes large doses of vitamins C and E, based on the assumption that these antioxidants may prevent nitric oxide inactivation by oxygen free radicals. Another study in 2010 by British researchers published in the Journal of Applied Physiology found that a beverage containing L-arginine improved the stamina of healthy, recreationally active men (Bailey, J Appl Physiol 2010). Compared to taking a placebo beverage, drinking a beverage containing 6 grams of L-arginine seemed to permit an extra two minutes or so of intense exercise before reaching exhaustion.

As noted in ConsumerLab.com's Review of L-Arginine Supplements, several studies also suggest that L-arginine supplements may be helpful in people with cardiovascular conditions such as angina or atherosclerosis. However, L-arginine may also increase the risk of death in patients recovering from a heart attack.

The Bottom Line:
Nitric oxide (NO) supplements don't actually contain nitric oxide (a gas) but include the ingredient L-arginine which may increase nitric oxide production in the body. L-arginine may improve circulation and, possibly, some aspects of exercise performance -- but probably not for well-trained athletes. Despite their popularity in bodybuilding circles, there's also no clear evidence that NO products lead to gains in strength, muscle size, or muscle "pump."

If you want to try L-arginine, it would be wise to choose a product that lists the actual amount of L-arginine on the label, as opposed to a proprietary blend that doesn't. A daily dose of about 6 grams per day has shown benefit for specific uses noted above. You can look at ConsumerLab.com's Review of L-Arginine Supplements for quality ratings and price comparisons of several L-arginine supplements. Be sure to review the Concerns and Cautions with L-arginine in that report, which includes a warning against L-arginine supplements if you have had a heart attack and potential effects on the stomach and insulin response.

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