Nitric Oxide: The Free Radical You Need

This unstable molecule has a critical role in keeping your blood full of nutrients and oxygen

Even though nitric oxide is produced naturally in the body, the amount varies from person to person, depending on diet and lifestyle. muse studio/Shutterstock

The health benefits of nitric oxide (NO) may not be as well known as those of popular nutrients such as iron or vitamin C, but that doesn’t mean they are less important.

This gaseous molecule is produced in the arteries and other parts of the body and plays an important role in immune function, athletic performance, diabetes management, and more.

Most of all, nitric oxide plays a critical role in maintaining blood vessel health.

Nitric oxide is a vasodilator, which means that it causes smooth muscle cells in the blood vessels to relax, allowing them to widen. This action increases blood flow, improves oxygen and nutrient delivery, and lowers blood pressure. These effects impact every part of the body and make NO a critical factor in cardiovascular health.

Even though NO is produced naturally in the body, the amount present varies significantly from person to person, largely depending on diet and lifestyle.

One of the most effective ways to boost the body’s production of NO is by consuming foods rich in amino acids and nitrates. One amino acid, L-arginine, is converted directly into nitric oxide in the body through a process called the L-arginine-NO pathway, while another, L-citrulline, is first converted to L-arginine and then into nitric oxide.

L-arginine is found largely in animal products including turkey, pork loin, chicken, beef, and fish, as well as in certain non-animal sources including pumpkin seeds, soybeans, and peanuts.

L-citrulline is found in a variety of melons, especially red and yellow watermelon and cantaloupe, as well as cucumbers and summer squashes. According to a study published in the journal Nutrients in July 2018, titled “L-Citrulline Supplementation: Impact on Cardiometabolic Health,” L-citrulline was effective at increasing NO synthesis, as well as reducing blood pressure in study subjects.

Study authors concluded that “L-citrulline supplementation represents an attractive non-pharmacological approach for increasing NO bioavailability, which may have the potential to counteract many of the age- and/or lifestyle-related diseases currently plaguing our society.”

Another way to boost nitric oxide production in the body is by consuming foods high in naturally occurring nitrates. Unlike synthetic nitrates, which are often added to processed meats as preservatives and which may pose significant health risks, many vegetables contain naturally occurring nitrates, and these are also converted to nitric oxide in the body.

When mixed with saliva and oral bacteria found on the back part of the tongue, these nitrates turn into nitrites, which are subsequently converted into nitric oxide. Many types of vegetables contain nitrates, but green leafy vegetables including spinach, arugula, and kale, along with beets, rhubarb, celery, and broccoli rank among the highest.

Nitric oxide molecules have a very short half-life—just a few seconds—and NO levels can rise or fall quickly. As a free radical that both builds up and breaks down very quickly in the body, it’s important to practice healthy, NO-boosting dietary and lifestyle habits on a consistent, regular basis.

Lou Ignarro, a leading research scientist who was honored with the Nobel Prize in Medicine for his discoveries on the function of nitric oxide as an important signaling molecule, said in an interview on “The Ultimate Health Podcast,” “As soon as you can digest the ingredients and get the components into the blood, that’s when you’ll see an increase in NO.”

The process also works in reverse, as Ignarro stated: “If you take a delicious, greasy, fatty hamburger, and you eat that, you’ll see a decrease [in NO] within 20 minutes to 40 minutes. And that decrease is going to be there two to four hours.”

Perhaps not surprisingly, the cumulative effect of a prolonged increase or decrease of nitric oxide will also have long-term effects on health.

In addition to eating plenty of foods that are rich in L-arginine, L-citrulline, and healthy nitrates, the nitric oxide that’s produced also needs to be maintained and protected from rapid degradation.

According to Ignarro, this is where consuming plenty of antioxidant-rich foods plays a critical role.

“The antioxidants take away oxidative stress, thereby allowing whatever nitric oxide that happens to be present to increase in amount, because it’s no longer being destroyed by the oxidative stress,” he notes.

To that end, think about including some blackberries or blueberries—both antioxidant superstars—or other antioxidant-packed foods as a regular addition to your diet, too.

Another way to boost the body’s nitric oxide production is through regular exercise.

Nitric oxide is produced by endothelial cells lining the blood vessels, and its production is boosted through exercise. Physical exercise increases blood flow, causing the blood vessels to dilate and transport more oxygen- and nutrient-rich blood, which in turn increases the health of the endothelial cells and boosts nitric oxide production.

Multiple studies have demonstrated the relationship between NO production and physical exercise, including one published in the September 1999 issue of the journal Circulation, which concluded that “long-term physical exercise improves endothelium-dependent vasorelaxation through an increase in the release of nitric oxide.”

This understanding has spawned a slew of “nitric oxide dump” exercise regimens: short, minutes-long fitness sessions that promise to quickly boost NO—and energy.

According to Ignarro, the nasal mucosa cells also produce a lot of nitric oxide, and inhaling through the nose, instead of the mouth, is an easy way to boost nitric oxide production, as well as to transport this important molecule to the lungs.

Another popular way to boost nitric oxide levels is through supplementation.

Nitric oxide supplements don’t actually contain nitric oxide itself (which, remember, is a gaseous molecule), but are likely to contain L-arginine, L-citrulline, or nitrates, all of which boost nitric oxide production. Athletes have used these supplements for decades to increase blood flow during workouts, with the hope of achieving longer, harder workouts, and faster, less painful post-workout recovery times.

According to Harvard Health, nitric oxide serves to keep the lining of the arteries smooth and slippery, preventing inflammation and blood clots, as well as relaxing the artery’s smooth muscle cells, allowing them to dilate effectively.

Understanding NO’s role in relaxing smooth muscle cells, and as a blood flow-increasing vasodilator played a pivotal role in the development of the erectile dysfunction drug Viagra, whose main ingredient, sildenafil, intensifies the relaxing effect of nitric oxide. Nitric oxide has also been used to lower blood pressure, and scientists are exploring its potential benefits in treating diabetes and improving heart health.

As science continues to learn more about the importance of this amazing molecule, one thing is clear—most of us could use more of it.