Will Nitric Oxide Supplements Boost Fitness Performance? Experts Explain

If boosting your performance and endurance in the gym (and in the bedroom) and improving your cardiovascular health are on your list of health goals, you might be considering nitric oxide supplements as a way to achieve them. But do they actually work?

First things first: 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. So, what is nitric oxide, then?

What is Nitric Oxide?

‘Nitric oxide is a gas and free radical that’s recognised 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 synthesised from L-arginine, an essential amino acid.

Nitric oxide acts as a vasodilator, which means it helps open blood vessels. As a result, many people take the precursor L-arginine for issues like erectile dysfunction and to improve heart health.

Nitric oxide’s role in vasodilation is also important for regulating blood pressure, says William Workman, M.D., an orthopaedic surgeon and sports medicine expert at DISC Sports and Spine Medicine in Walnut Creek, California.

Many small blood vessels and capillaries sit dormant until you get your heart rate up during exercise, and nitric oxide enables blood to flow to these areas to allow your muscles to work, hence its reputation as a substance that can help your fitness performance.

Other important functions of nitric oxide are its roles in neurotransmission, hormone signalling, 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.

What Are Nitric Oxide Supplements?

Often our supplements don’t actually contain nitric oxide; they just contain its precursors: L-arginine and sometimes L-citrulline. ‘Supplementation of these compounds provides the body with the building blocks for nitric oxide production,’ Anzures says. L-arginine also helps the body build protein.

‘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 Anzures.

The Potential Benefits of Nitric Oxide

So far here’s what we know about nitric oxide and its potential benefits:

Nitric Oxide Could Boost Your Fitness Performance

On 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.)

It Could Improve Your Blood Pressure

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. The theoretical mechanism for supplementing with L-arginine to increase nitric oxide production is its role in blood flow and blood pressure regulation.

It Could Help You Last Longer In Bed

The blood flow regulation that nitric oxide helps with plays a role in multiple body functions, including maintaining erections.

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, some research suggests.

It Could Help Lower Your Risk for Heart Disease

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 cardiovascular 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.

It Might Help With Respiratory Illnesses

A 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.

Are Nitric Oxide Supplements Safe?

Experts are mixed on whether you should take them, because there’s not clear evidence that they work. But Dr. Workman says taking them is generally harmless for most people, you don’t go overboard (see side effects and information on who shouldn’t take them, below): ‘If people feel like they’re struggling to get their exercise level to where they want it and feel like they’re not able to recover, it’s worth trying,’ he says.

There’s no typically recommended dose of nitric oxide supplements. However, Rothstein says, ‘Doses between 6 to 13 grams are usually used in research studying L-arginine, and this appears to be tolerated well by most people.’

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.

Experts say your body makes enough nitric oxide naturally, so supplements generally aren’t necessary. And, according to a statement from the United States Anti-Doping Agency, supplements aiming to improve nitric oxide may contain large amounts of other ingredients like caffeine.

Keep in mind, too, that supplements are not regulated by the U.S. Food and Drug Administration like prescription and over-the-counter medications, Anzures adds.

Nitric Oxide Side Effects

Gastrointestinal issues like vomiting and diarrhea, are the most common side effects of nitric oxide supplements, Rothstein says.

Taking too much nitric oxide could potentially lead to ‘a massive vasodilation,’ causing a drop in blood pressure and possibly leading to a stroke, Dr. Workman says.

Dizziness and headaches might happen too, Anzures says. ‘More serious side effects are allergic reaction and difficulty breathing.’

Who Shouldn’t Take Nitric Oxide?

According to a recent study, 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.

Can You Get Nitric Oxide in Food?

Yes, and Dr. Workman says food sources of nitric oxide are always preferred to supplements. ‘They’re going to have that plus an almost unlimited number of beneficial ingredients in the form of antioxidants and vitamins,’ he adds.

The precursor compounds of L-arginine and L-citrulline can be found in foods that are high in protein (both compounds are amino acids), including 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, says Natalie Rizzo, M.S., R.D., a New York City-based registered dietitian.

‘One study found cyclists who drank beetroot juice two to three hours before exercise increased peak power and pedalling velocity,” Rizzo says. “Another review also shows that beetroot juice can increase overall endurance and power for athletes.’

Beets are also linked to increased strength and endurance performance as well as improvements in cognition during exercise, lower inflammation levels, greater antioxidant function, improved cognition, and more.

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