Nitric oxide is a compound in the body that causes blood vessels to widen and stimulates the release of certain hormones, such as insulin and human growth hormone.

Nitric oxide supplements are a category of supplements that includes L-citrulline and L-arginine. Researchers have performed multiple clinical trials related to nitric oxide supplements and their effectiveness, often with mixed results.

This article will examine how nitric oxide works in the body and some of the reported health benefits and risks of nitric oxide supplementation.

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Nitric oxide supplements may relax or widen blood vessels.

The two most common nitric oxide supplements are L-arginine and L-citrulline.

L-arginine is an amino acid, or a protein building block, naturally found in red meat, dairy products, poultry, and fish. Manufacturers produce it in a laboratory as a pill, powder, or cream.

L-citrulline is also an amino acid found in meat, nuts, legumes, and watermelon. Manufacturers can also make L-citrulline in a laboratory and package it as a pill or powder.

Without taking nitric oxide supplements, a person typically consumes about 5 grams (g) of L-arginine per day, according to an article in The Journal of Nutrition. The body converts this into nitric oxide for use in various body functions.

Some scientists believe that nitric oxide in the body relaxes or widens blood vessels. Some medications, such as Viagra harness the nitric oxide pathway to promote blood vessel widening and improve blood flow to the penis to enhance erections.

Many people think that taking nitric oxide supplements will enhance blood flow in the body to improve performance in sports, promote healing, enhance heart health, and provide many other potential benefits.

While there are many potential uses and benefits for nitric oxide supplements, there is not a lot of research to support some of the claims.

This is what the science says about the benefits of taking nitric oxide:

Improves heart health

According to an article published in the journal Biochemical and Biophysical Research Communications, taking nitric oxide supplements offers several heart boosting effects. These include reducing arterial stiffness, reducing blood pressure, and improving carotid artery blood flow. However, it is important to note that the researchers studied animals, not humans, to find these effects.

Enhancing exercise and recovery

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A person may take nitric oxide supplements to improve athletic performance.

Researchers theorize that taking nitric oxide supplements could enhance the delivery of oxygen to muscles. This could potentially improve athletic performance and reduce soreness after a workout.

According to an article in the journal Sports Medicine, studies have shown that taking nitric oxide supplements may enhance tolerance to exercise. However, this only applies to those who did not exercise regularly or only exercised at a moderate rate.

The research has not shown that nitric oxide supplements can help elite athletes. Researchers carried out these studies on young males, so they do not know how nitric oxide supplements may affect older people and females.

Reducing erectile dysfunction

Because nitric oxide supplements enhance blood flow, researchers have conducted studies to determine if it could enhance blood flow for people with erectile dysfunction (ED).

According to an article in the journal Future Science OA, some studies have shown taking nitric oxide may reduce ED in those with mild to moderate ED.

Reducing high blood pressure in pregnancy

Preeclampsia, which is a form of high blood pressure that can occur in pregnancy, can be dangerous for both the woman and baby.

A 2005 study in the European Journal of Clinical Investigation found that pregnant women who took L-arginine supplements for a prolonged period had lower blood pressure readings than pregnant women who did not take L-arginine.

Although researchers need to conduct more studies, the results are promising for women struggling with high blood pressure in pregnancy.

Future research

These are just some examples of more extensive studies that examined the effectiveness of nitric oxide.

However, there are no studies that establish how much nitric oxide supplements people should take to achieve the same results as the study participants did.

People take nitric oxide for a variety of reasons, many of which do not have any scientific research to support them.

Some of the reported benefits of nitric oxide supplements include:

  • enhancing weight loss
  • improving lung function in those with cystic fibrosis
  • treating altitude sickness
  • improving recovery after major trauma or injury
  • preventing the common cold
  • reducing the side effects of memory loss
  • healing diabetic foot ulcers

Most of these benefits are anecdotal, meaning that people may have reported a benefit, but there is no proof backed up by a scientific study.

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A person should talk to a doctor about any interactions nitric oxide supplements may have with existing medications.

For most people, taking nitric oxide supplements does not cause side effects. When side effects do occur, they are often mild and may include:

However, some people should not take the supplements because of the risk of potential side effects. These include people with:

  • Cirrhosis: People with cirrhosis, or liver scarring, should take nitric oxide cautiously as it could worsen liver function.
  • Guanidinoacetate methyltransferase deficiency: This is a rare genetic condition where a person lacks an enzyme that converts arginine into creatine, which is a waste product. As a result, people with this deficiency should not take nitric oxide supplements.
  • Low blood pressure: If a person already has low blood pressure, they should not take nitric oxide supplements due to the risk that it might lower blood pressure further. Doctors will recommend that anyone taking nitric oxide supplements stops doing so before undergoing surgery.

Doctors also have some concerns that taking nitric oxide supplements could make some conditions worse. These include kidney disease, herpes, and after a person has had a heart attack.

A study published in 2006 in JAMA found that people taking L-arginine after a heart attack had a higher chance of death, experiencing a repeat heart attack, and being hospitalized than people who did not.

This article does not give a comprehensive list of potential conditions where a person should not take nitric oxide supplements.

The supplements may also interfere with medications, such as those for diabetes and high blood pressure. Anyone thinking about taking nitric oxide supplements should talk to their doctor first to ensure they will not interfere with existing conditions or any other medications they are taking.

Nitric oxide supplements have been available for decades, but as there is little scientific evidence to back up their use for specific health benefits, doctors do not routinely recommend them.

Instead, doctors may prefer to recommend lifestyle modifications or medications that scientists have proven to treat medical conditions effectively.

Nitric oxide supplements do not cause many side effects in most people, so some people might choose to try them. However, individuals should make sure that they do not have specific medical conditions that nitric oxide could harm.

A person should always talk to their doctor before taking nitric oxide or any other supplement to make sure they are making a safe, healthful choice.