Until a few decades ago, researchers paid little attention to nitric oxide’s role in the body. It had long been known that we exhale tiny amounts of this chemical compound and that it’s an air pollutant from cars and factories. But scientists didn’t know that nitric oxide does so much in the body.
That changed in the 1980s and 1990s, when the significance of nitric oxide as a chemical messenger in all mammals was established. Nitric oxide’s physiological importance was officially recognized in 1998 when a Nobel Prize was awarded to three scientists who discovered that it is a vital molecule in the cardiovascular system and helps keep blood vessels healthy and regulate blood pressure. Since then, nitric oxide has also been found to be essential in many other bodily systems (such as the immune system and the nervous system, including the brain) and to play an important role in many chronic conditions and diseases (such as chronic inflammation, erectile dysfunction, and cancer). This has led researchers to focus on nitric oxide as a potential target for medical therapies.
Like many key compounds in the body, nitric oxide can be a double-edged sword. Produced by the body in small amounts where it is needed, it is essential and helps maintain health. But in larger amounts, it can be harmful and damage cells.
How does nitric oxide affect the heart and blood vessels?
Released by the inner layer of cells (endothelium)of blood vessels, nitric oxide relaxes the vessels and keeps them flexible, allowing them to dilate, boosting blood flow, and helping to control blood pressure. Nitric oxide also has anti-inflammatory effects and helps prevent platelets and white blood cells from adhering to the lining of blood vessels, thus reducing the risk of plaque development.
As we age, our cells produce less nitric oxide, so blood vessels become less flexible, which contributes to hypertension, inflammation in blood vessels, and atherosclerosis (plaque buildup)-that is, cardiovascular disease. And there’s a vicious cycle: High blood pressure, inflammation, and atherosclerosis, in turn, impair the production and action of nitric oxide.
What foods boost nitric oxide?
Vegetables-notably beets and leafy greens-contain nitrates, which can be converted in the body to nitrites and then to nitric oxide. Studies have shown that beet juice, for instance, can help lower elevated blood pressure, which has been attributed to the ability of its nitrates to boost nitric oxide. A recent review in the American Journal of Clinical Nutrition summarized research showing the beneficial effects of dietary nitrates on blood pressure, arterial stiffness, platelet function, and cerebral blood flow. (Nitrate supplements are marketed primarily to athletes, but research on their effect on performance has had inconsistent results.)
Many plant foods, including fruits, chocolate, garlic, and red wine, also provide polyphenols and other compounds that can increase nitric oxide production in the body via a variety of pathways.
Cells use arginine, an amino acid (a building block of protein), to make nitric oxide. High-protein foods such as turkey, seafood, dairy, beans, nuts, and seeds supply arginine. A study in the journal Nutrients in 2016 found that higher dietary intake of arginine was strongly linked with higher blood levels of nitrites and nitrates, which are a measure of nitric oxide production.
Are arginine supplements a good idea?
Studies show that arginine supplements can boost the body’s nitric oxide production. A few have also suggested that the supplements can improve the function of blood vessels, enhance coronary blood flow, lower blood pressure, and even reduce angina or other symptoms in people with cardiovascular disease. But several clinical trials have found that supplemental arginine did not help people with cardiovascular disease and may actually have worsened their condition.
In sum, the benefits of arginine supplements are uncertain and their long-term safety unknown. Increased amounts of one amino acid may create imbalances with other amino acids and have adverse effects. And increased nitric oxide might be dangerous for people with certain medical conditions.
Should you have your nitric oxide level measured by an OTC test kit?
No. Nitric oxide is difficult to assess except in laboratories doing experimental research. Blood or saliva levels of nitrite may or may not reflect nitric oxide bioavailability in the body. Currently, there is no valid, reliable test for nitric oxide available to the public. Saliva test strips on the market that claim to measure nitric oxide are not likely to accurately assess nitric oxide bioavailability, according to a paper in the journal Nitric Oxide in 2015.
BOTTOM LINE: The best way to maintain healthy nitric oxide levels and keep blood vessels healthy is to eat a varied plant-based diet. Exercising regularly also helps enhance nitric oxide generation. This is one way a heart-healthy diet and exercise help improve cardiovascular health and health in general. And don’t smoke: Smoking impairs nitric oxide function in the body.