Can Nitric Oxide Supplements Really Boost Your Fitness? Here’s What the Experts Say
Experts break down the buzz surrounding these popular supplements.
If you’re aiming to enhance your workout performance, increase endurance (in the gym and the bedroom), and support cardiovascular health, you might be eyeing nitric oxide supplements. But do they live up to the hype?
First Things First: What Is Nitric Oxide?
Let’s clear up a common misconception: nitric oxide is not the same as nitrous oxide—the “laughing gas” used at the dentist. So, what exactly is it?
“Nitric oxide is a gas and a free radical that plays a role in various physiological systems,” explains Alex Rothstein, M.S., an exercise science instructor at the New York Institute of Technology. It’s produced in the body from the amino acid L-arginine.
Nitric oxide works primarily as a vasodilator, meaning it relaxes and widens blood vessels to promote better blood flow. This is why L-arginine is often taken for conditions like erectile dysfunction or to support heart health.
Its ability to open up blood vessels is also crucial for regulating blood pressure, adds Dr. William Workman, an orthopedic surgeon and sports medicine specialist at DISC Sports & Spine Center in California.
When you exercise and your heart rate increases, many smaller blood vessels that are typically inactive get activated. Nitric oxide facilitates this, enhancing muscle performance and endurance, which is why it’s commonly associated with improved fitness performance.
Aside from boosting blood flow, nitric oxide also plays key roles in neurotransmission, hormone signaling, and overall vascular relaxation, according to Marco Anzures, M.S., C.S.C.S., owner of Coach You Better and instructor at San Diego City College.
What Are Nitric Oxide Supplements?
Despite the name, most nitric oxide supplements don’t contain nitric oxide itself. Instead, they include precursor compounds like L-arginine and L-citrulline.
“These precursors supply the raw materials the body needs to produce nitric oxide,” Anzures explains. L-arginine also supports protein synthesis, according to the Mayo Clinic.
However, the science is still evolving. “Research connecting these precursors to improvements in heart health, exercise performance, and erectile dysfunction is mixed and not overwhelmingly conclusive,” says Anzures.
Potential Benefits of Nitric Oxide
1. May Enhance Fitness Performance
Nitric oxide’s primary fitness claim to fame is improved blood flow, which helps deliver oxygen and nutrients to working muscles. This can potentially help you push harder and recover faster during workouts.
Some studies suggest that L-arginine supplementation may improve performance in endurance sports like running, cycling, and swimming—but other studies found minimal or no effect.
“The research is mixed,” says Anzures. “There’s some evidence supporting better endurance, but little to no impact on short-term performance or time trials.”
One small study found that L-citrulline might boost aerobic performance and reduce muscle soreness post-exercise. Another review showed that nitric oxide-related supplements might help with exercise tolerance in untrained or moderately trained individuals, but not in elite athletes.
2. Could Help Regulate Blood Pressure
High blood pressure can lead to serious health issues like heart disease and stroke. Because nitric oxide supports vasodilation, it may play a role in lowering blood pressure—especially in people with lower baseline nitric oxide levels.
3. May Support Sexual Health
Improved blood flow also means potential benefits for sexual performance. A 2020 study found that L-arginine might enhance the effects of certain erectile dysfunction medications. L-citrulline has also shown promise in supporting erectile function, although more research is needed—especially for people without pre-existing issues.
4. Might Reduce Risk of Heart Disease
In people who don’t exercise regularly, nitric oxide supplements might help compensate for reduced vasodilation. “If someone isn’t getting enough arginine through diet or exercise, supplementation may help,” Rothstein says.
Nitric oxide production is often impaired in people with type 2 diabetes, which can lead to poor vascular health. Supplements might help reduce some of these risks.
5. Could Aid Respiratory Illness Treatment
A study by Chinese and American researchers found that inhaled nitric oxide might help treat severe Covid-19 cases. Its ability to dilate blood vessels could be useful in managing other respiratory or cardiovascular complications as well.
Are Nitric Oxide Supplements Safe?
Expert opinions vary, but generally, nitric oxide supplements are considered safe for most people—when used in moderation. “If someone’s struggling with performance or recovery, trying a supplement may be worthwhile,” Dr. Workman says.
Research studies typically use 6 to 13 grams of L-arginine, and these amounts are usually well-tolerated. Still, Anzures strongly recommends checking with your doctor first—especially if you have any underlying health issues or are on medication.
Your body naturally produces enough nitric oxide, so supplements often aren’t necessary for healthy individuals. Plus, many nitric oxide products contain added stimulants like caffeine, which can affect how your body responds.
Also worth noting: supplements are not regulated by the FDA the same way medications are, so quality and dosage can vary widely.
Potential Side Effects
- Digestive issues like vomiting and diarrhea are the most common side effects.
- Excessive intake could cause excessive vasodilation, leading to a dangerous drop in blood pressure and potential risk of stroke.
- Headaches, dizziness, and even allergic reactions are possible, Anzures says.
Who Should Avoid Nitric Oxide Supplements?
People with certain medical conditions should steer clear, including those with:
- Liver cirrhosis
- Low blood pressure
- Kidney disease
- Herpes
- Heart disease
Also, if you’ve had a heart attack, nitric oxide supplements could increase the risk of complications, including GI issues and additional cardiac events.
Can You Get Nitric Oxide from Food?
Absolutely—and experts say that’s the best way.
“Food sources come with the added benefits of antioxidants, vitamins, and other nutrients,” says Dr. Workman.
Foods high in L-arginine and L-citrulline include:
- Beans and legumes
- Red meat
- Dairy
- Fish
- Nuts and seeds
Vegetables, especially beets and leafy greens like arugula and spinach, are rich in nitrates that convert to nitric oxide in the body.
“Cyclists who drank beetroot juice before workouts showed increased power and endurance,” says Natalie Rizzo, M.S., R.D. “Beets have also been linked to reduced inflammation, better brain function during exercise, and enhanced strength.”
The Bottom Line:
While nitric oxide supplements might offer performance or health benefits for some people—especially those who are less active or nutrient-deficient—the science is still mixed. For most, a nutrient-rich diet and regular exercise are likely more effective (and safer) ways to support nitric oxide production and overall health.