EVERYONE IS LOOKING for ways to boost their performance and endurance in the gym (and the bedroom) and improve their cardiovascular health. And, some consider nitric oxide supplements as a way to do that. But, do these supplements actually work? And, uh, what the heck is nitric oxide anyway?
The first thing to know is that nitric oxide isn’t the same as nitrous oxide, also known as laughing gas, or the stuff that gets you a little high at the dentist. “Nitric oxide is a gas and free radical that’s recognized to play a role in several physiological systems,” says Alex Rothstein, M.S., an instructor in the exercise science program at the New York Institute of Technology. “It’s synthesized from L-arginine (an essential amino acid), and this is why many supplements that suggest an increase in nitric oxide use L-arginine.”
Most nitric oxide supplements don’t actually contain nitric oxide. Instead, they tend to use L-arginine to “enzymatically synthesize nitric oxide in a number of bodily tissues,” Rothstein says.
L-arginine helps the body build protein, according to the Mayo Clinic. Your body usually makes enough L-arginine on its own, and you can get it through foods like fish, meat, beans, and dairy. It also acts as a vasodilator, which means it helps open blood vessels. So, many people take L-arginine for things like erectile dysfunction and to treat heart conditions.
While nitric oxide is essential for vasodilation, research doesn’t necessarily support the claim that L-arginine supplements produce more nitric oxide than normal dietary intake and exercise, Rothstein says.
Interestingly, a new study from a team of Chinese and American researchers found that inhaled nitric oxide could potentially be a treatment for critically ill COVID-19 patients. It’s thought that nitric oxide’s vasodilation properties may serve as effective therapy not just for COVID, but for other respiratory and cardiovascular conditions related to the virus.
“Nitric oxide is a gas that the body produces, and it helps with blood flow,” says Natalie Rizzo, M.S., R.D.
Nitric oxide is associated with roles in neurotransmission, hormone signaling, and the relaxation of blood vessels, explains Marco Anzures, M.S., C.S.C.S., owner of the coaching platform Coach You Better and an exercise science instructor at San Diego City College.
“Nitric oxide supplementation most commonly involves the precursor molecules L-arginine and L-citrulline,” he says. “Precursors are compounds involved in the creation of another compound. Supplementation of these compounds provides the body with the building blocks for nitric oxide production.”
Some say supplementing with nitric oxide increases the amount of the substance in your blood, which might bring several health benefits. But, the science is inconclusive.
“The research linking the consumption of the precursor molecules to increase nitric oxide and subsequently improve markers of heart health, exercise performance, and treating erectile dysfunction (to name a few) is mixed and not strongly supported by the literature,” says Azures, who usually doesn’t recommend nitric oxide supplements.
If you’re looking to give nitric oxide a try, here’s what you should know.
There’s not enough evidence on use or formulations to be able to say for sure. Experts say your body makes enough nitric oxide naturally, so supplements aren’t necessary. And according to a statement from the United States Anti-Doping Agency, pre-workout supplements like these may contain large amounts of other ingredients like caffeine.
So far, here's what we know about nitric oxide and its potential benefits:
One of the primary functions of nitric oxide is widening blood vessels to increase blood flow, or vasodilation, Rothstein says. This helps deliver oxygen and nutrients to your muscles when you exercise, which could help you perform better and work out longer.
Some research shows that L-arginine, found in nitric oxide supplements, could improve fitness performance for runners, cyclists, and swimmers. But, other research has shown little to no effect.
“The research is mixed on the purported benefits of nitric oxide supplementation and fitness performance,” Anzures says. “There is some evidence to suggest supplementation helps with endurance but not with overall performance in a time trial.”
A small study also showed that L-citrulline could help boost aerobic performance and decrease muscle soreness after working out.
A review of several studies related to the effects of dietary ingredients linked with nitric oxide and exercise performance found mixed results: the review concluded that while nitric oxide supplements may "improve tolerance" to aerobic and anaerobic exercise in people who either aren't in shape or are moderately trained, there seems to be no benefit in highly trained people.
More research is needed to know for sure whether the supplements actually play a role in your workout performance. (But these supplements may help you get extra benefits from lifting.)
High blood pressure happens when the force of the blood that pushes against the walls of your blood vessels is too high. This can cause health consequences like heart disease and stroke. It’s believed that people with high blood pressure aren’t able to use nitric oxide in their bodies.
“The theoretical mechanism for supplementing with L-arginine to increase nitric oxide production is that nitric oxide has a number of very important physiological roles,” Rothstein says. One is blood flow and blood pressure regulation.
The blood flow regulation that nitric oxide helps with plays a role in multiple body functions, including maintaining erections. Along with erections, it could increase performance in bed and help you last longer.
A 2020 study showed that L-arginine supplements might enhance the effects of a common erectile dysfunction drug, but studies on people without a dysfunction are limited. So, the general benefits aren’t totally known. L-citrulline might also help treat erectile dysfunction, research shows.
Along with helping improve blood pressure, nitric oxide might reduce your risk for heart disease, especially for people who don’t exercise regularly, Rothstein says.
“For these individuals, an increase in L-arginine may promote vasodilation that would not otherwise occur without the onset of exercise,” he adds. “If an individual for some reason was also not ingesting enough arginine in their diet, supplementation would help offset the lack of this nutrient.”
Supplements might also reduce the effects of type 2 diabetes. Nitric oxide production is also hindered in people with type 2 diabetes, and this diminishes the health of blood vessels, which increases the risk of heart disease and high blood pressure.
While it’s tough to say whether nitric oxide supplements work, because there’s not enough evidence, they're safe for most people. Just don’t take too much.
“Doses between 6 to 13 grams are usually used in research studying L-arginine, and this appears to be tolerated well by most people,” Rothstein says.
Anzures urges anyone considering taking nitric oxide supplements to talk to their doctor first, especially if you have high blood pressure, heart problems, or any other health condition or take medications.
Keep in mind, too, that supplements are not regulated by the U.S. Food and Drug Administration like prescription and over-the-counter medications, he adds. The supplements might also contain additional ingredients so always check the label.
Gastrointestinal issues, like vomiting and diarrhea, are the most common side effects of nitric oxide supplements, Rothstein says.
Dizziness and headaches might happen too, Azures says. “More serious side effects are allergic reaction and difficulty breathing.”
According to a recent study from a team of Italian and American researchers, people with
conditions including liver cirrhosis, guanidinoacetate methyltransferase deficiency and low blood pressure should be wary when it comes to nitric oxide. The risk of the supplement’s side effects could be higher if you have any of these medical issues. You should also be very careful about taking nitric oxide if you have kidney disease, herpes, or heart conditions. People who’ve had heart attacks and subsequently take nitric oxide are not only at risk for repeated heart attack, but GI problems as well. So you can see, despite the fact that nitric oxide is touted as a possible boost to your heart health, for some people, the opposite effect is true.
Yes, and consuming foods rich in the precursors to nitric oxide is preferred to supplements.
“The precursor compounds of L-arginine and L-citrulline can be found in foods that are high in protein (both compounds are amino acids) like beans, legumes, red meat, dairy products, fish, and nuts, and seeds,” Anzures says. “A proper diet should provide enough support for the proper creation of nitric oxide by the body for healthy individuals.”
Vegetables, especially beets and leafy greens, like spinach and arugula, are rich in nitrates, which are associated with higher nitric oxide levels in the body, Rizzo says.
“One study found cyclists who drank beetroot juice two to three hours before exercise increased peak power and pedaling velocity,” Rizzo says. “Another review also shows that beetroot juice can increase overall endurance and power for athletes.”
