In recent years, there has been growing interest in nitric oxide (NO), which plays an important role in the cardiovascular system and is involved in a number of other functions in the body. Nitric oxide supplements are designed to increase nitric oxide production in order to support these functions.
But do nitric oxide supplements actually work? This article will take a look at what the research says about the benefits of supplementation.
What Does Nitric Oxide Do?
Nitric oxide (not to be confused with nitrous oxide, a gas used as a sedative) is a signaling molecule that is especially important in the cardiovascular system. It acts as a vasodilator, which means it opens up blood vessels by stimulating muscles in the walls of arteries and veins, causing them to relax. This results in an increase in blood flow and well as a decrease in blood pressure. It is also connected to blood clotting and helps to protect against the formation of plaque in arteries, contributing to heart health.
Increased blood flow means more oxygen and nutrients to the tissues of the body, which is why nitric oxide is also important for exercise performance and energy levels. It contributes to energy in another way, however, since it also helps to adjust energy supply to meet demand by stimulating the cell’s mitochondria, the center of cellular energy production.
Something else connected to blood flow is sexual function in men. The effectiveness of Viagra is due to its ability to increase blood flow to the penis. Since nitric oxide increases blood flow, it has been found to be connected to erectile dysfunction. (1)
Beyond these things, nitric oxide has also been found to play a role in immune function, cell growth, and insulin response.
In other words, it is a pretty important molecule in our bodies. You can see why nitric-oxide-related supplements are growing in popularity. In the next section, we'll take a look at how these supplements are supposed to work before considering the available research.
Nitric Oxide Supplements
The body gets the nitric oxide it needs by two different pathways. One involves nitric oxide production from the amino acid L-arginine. In the other pathway, the body breaks down nitrate or nitrite found in food to form nitric oxide.
Nitric oxide supplements contain ingredients that aim to increase nitric oxide naturally by one of these two pathways (or both). L-arginine is a common supplement ingredient, since it is the chemical from which the body makes nitric oxide.
However, L-arginine does not seem to be as bioavailable in a supplement form. (In other words, the body isn't able to make use of it efficiently.) A different amino acid, L-citrulline, is converted in the liver to L-arginine and seems to be a more effective source for this amino acid. (2)
Besides amino acids, nitric oxide supplements may also contain concentrated forms of foods that are rich in nitrates or nitrites, like beet juice or spinach. Research has shown that supplementation with L-arginine and L-citrulline is able to increase concentrations of L-arginine in the blood, supporting nitric oxide production. (3) Obviously, our bodies are also able to make use of the nitrates naturally found in the foods we eat.
Potential Benefits of Nitric Oxide Supplementation
We know a lot about the role that nitric oxide plays in the body (even if there is likely lots more to discover). We also know, as noted above, that ingesting sources of nitric oxide in supplements or in food is able to increase the bioavailability of the building blocks the body uses to produce it. This appears to have a positive impact on how much nitric oxide our bodies make.
The body is an incredibly complex system, however, and the pathways that lead from dietary supplements to certain effects in the body are not always clear or well understood. That's where research comes in; it helps us discover patterns and gain a better understanding of the potential positive effects of supplements. In this section, we highlight several areas where research has shown promise of health benefits from nitric oxide supplements.
Increased Exercise Performance
One meta-analysis (a study that looks at a number of other published studies) published in Sports Medicine found that nitric oxide supplements taken by healthy individuals who were untrained or moderately trained could improve tolerance for both aerobic and anaerobic exercise. This makes sense, since nitric oxide seems to be involved in oxygen and nutrient delivery to working muscles.
However, the study notes that the research to date contains mixed results. For athletes who were already highly trained, nitric oxide supplements were not able to improve performance. For most of us, however, a nitric oxide booster may be helpful for improving workout performance.
Lowered Blood Pressure
If you've read this far, you already know that nitric oxide is a vasodilator, which is able to lower blood pressure by relaxing the muscles that line the walls of blood vessels. It would make sense that nitric oxide supplements would lead to lower blood pressure by supporting the body's nitric oxide production, and research backs this idea up.
One clinical trial tested nitric oxide supplements with a group of patients who had high blood pressure. It found that taking nitric oxide supplements was able to significantly reduce both systolic and diastolic blood pressure shortly after taking the supplements. (4)
Another trial looked at the effects of supplementation with L-arginine on pregnant women. One of the common (and potentially dangerous) complications of pregnancy is elevated blood pressure, called preeclampsia. This study found that nitric oxide supplements were effective in lowering blood pressure in pregnant women, making this a possible safe and effective means of decreasing risks for this condition. (5)
Greater Cardiovascular Health
Nitric oxide plays a role in a number of mechanisms that protect the health of your heart and blood vessels. As we have already discussed, it lowers blood pressure. It also helps to prevent the formation of plaque on artery walls. One study reports that supplementation with L-citrulline is effective in increasing plasma L-arginine levels, which in turn leads to more nitric oxide production. This is associated with improvements in a number of markers that are linked with improved heart health and the reduced risk of heart attack. (6)
Improved Erectile Function in Men
Erectile dysfunction is connected to problems with blood flow, and nitric oxide plays an important role in this. Researchers have speculated that nitric oxide supplements may be able to enhance blood flow in order to improve the condition.
One randomized clinical trial found that L-arginine supplements showed a promising ability to treat erectile dysfunction. (7)
Since L-arginine is safe and well-tolerated, the researchers suggest this may be an effective treatment for mild cases of erectile dysfunction. At this point, however, more research is needed.
Since we know that nitric oxide is involved in so many body processes, researchers will likely continue to discover many benefits of nitric oxide supplements. We also know that L-arginine has other roles in the body besides the production of nitric oxide.
One other interesting area, for example, has to do with the regulation of insulin and the way the body stores fat. Some studies have suggested that L-citrulline and L-arginine supplements may have a role in fighting obesity. (8)
At this point, we can confidently say this much: There is scientific evidence that supplements that act as nitric oxide boosters seem to have a number of beneficial impacts on overall health.
Are Nitric Oxide Supplements Safe?
Despite all these potential benefits of increasing nitric oxide levels, it is natural to wonder about the safety of taking nitric oxide supplements. An article in The Journal of Nutrition discusses the research to date on the safety of specifically L-arginine supplements and finds that the existing data indicate they do not produce adverse effects. (9)
An FDA report on L-citrulline found that there is not a lot of good data presently on the safety of this supplement. However, the report did note that it has been in use for decades and is not associated with any adverse effects. (10)
As we mentioned above, we get the precursors for nitric oxide naturally from our diet. Some of the richest sources are beets, spinach, and other leafy greens like arugula. Nitrates are found at varying levels in other vegetables, too, as well as in processed meats. Eating vegetables, then, means taking advantage of natural nitric oxide boosters that we know have other health benefits as well.
What Is the Best Nitric Oxide Supplement?
When selecting a nitric oxide supplement, the information presented in this article should be helpful. You'll know that our bodies synthesize nitric oxide by two different pathways - one by using the building block L-arginine and the other by modifying forms of nitrate from food. The best nitric oxide supplements will contain ingredients that target both of these pathways, maximizing the availability of the precursors of nitric oxide in your blood and ultimately raising nitric oxide levels.
Remember also that L-citrulline is an especially effective chemical that your body converts to L-arginine.
You can find one example of a high-quality supplement that provides plant-based precursors as well as the amino acids L-arginine and L-citrulline here.