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Nitric oxide can increase blood flow and reduce blood pressure. Supplements that increase nitric oxide production may also be beneficial for managing certain health conditions.

Nitric oxide is produced naturally by the human body and is one of the most important molecules for blood vessel health (1).

It’s a vasodilator, meaning it relaxes the inner muscles of your blood vessels, causing the vessels to widen. In this way, nitric oxide increases blood flow and lowers blood pressure (2).

Supplements that increase nitric oxide in the body make up one of the most popular supplement categories today.

These supplements don’t contain nitric oxide itself. However, they contain compounds that your body can use to make nitric oxide and have been shown to provide many benefits for health and performance.

Here are 5 health and performance benefits of taking nitric oxide supplements.

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1. Helps treat erectile dysfunction

Erectile dysfunction (ED) is the inability to achieve or maintain an erection firm enough for sex (3).

L-citrulline is an amino acid that may help treat erectile dysfunction by increasing the production of nitric oxide (4).

Nitric oxide is needed for the muscles in the penis to relax. This relaxation allows chambers inside the penis to fill with blood so the penis becomes erect (5).

In one 2011 study, L-citrulline was found to improve erection hardness in 12 people with mild erectile dysfunction (6).

Researchers concluded that L-citrulline was less effective than prescription drugs used to treat ED, such as Viagra. Nevertheless, L-citrulline proved to be safe and well tolerated (6).

Two other nitric-oxide-boosting supplements have been shown to treat erectile dysfunction, inclduing the amino acid L-arginine and French maritime pine bark extract.

In several older studies, a combination of L-arginine and French maritime pine bark extract significantly improved sexual function in people with ED (7, 8, 9).

When taken together, L-arginine and French maritime pine bark extract also appear safe (10).

Nitric oxide plays an important role in erectile function. Several supplements, including L-citrulline, L-arginine, and French maritime pine bark extract, have been shown to increase levels of nitric oxide in people with erectile dysfunction (ED).

2. May decrease muscle soreness

A form of L-citrulline called citrulline malate not only increases nitric oxide production, but also decreases muscle soreness.

Muscle soreness is an uncomfortable experience that tends to occur after strenuous or unaccustomed exercise (11).

This soreness is referred to as delayed-onset muscle soreness and usually feels the strongest 24–72 hours after exercise (11).

In one 2010 study, 41 people were randomized to receive either 8 grams (g) of citrulline malate or a placebo 1 hour before performing as many repetitions as possible on a flat barbell bench press (12).

Those given citrulline malate reported 40% less muscle soreness at 24 and 48 hours after the exercise, compared to those who took the placebo (12).

Citrulline malate increases nitric oxide production, which increases blood flow to active muscles. In turn, citrulline malate is thought to increase nutrient delivery and clear waste products that are related to muscle fatigue, such as lactate and ammonia (13).

However, a later study on the effects of citrulline after leg exercises did not find citrulline malate helpful for the treatment of muscle soreness (14).

Another review of 13 studies showed that while citrulline could reduce muscle soreness 24 hours and 48 hours after exercise, it did not improve muscle soreness 72 hours after exercise (15).

Therefore, the ability of citrulline malate to decrease muscle soreness may depend on the dose, exercise, and timing. However, more research on this is needed.

Citrulline malate is a form of L-citrulline that may help alleviate muscle soreness by increasing nitric oxide. The dose and type of exercise may affect the ability of citrulline malate to decrease muscle soreness.

3. Lowers blood pressure

People with high blood pressure are thought to have an impaired ability to use nitric oxide in their bodies (16).

High blood pressure occurs when the force of your blood pushing against the walls of your arteries is consistently too high. It is defined as systolic blood pressure above 130 millimeters of mercury (mmHg) and/or diastolic blood pressure higher than 80 mmHg (17).

Over time, high blood pressure can lead to health issues such as heart disease and kidney disease (18, 19).

It has been shown that a diet high in fruits and vegetables decreases blood pressure and therefore lowers the risk of disease (20).

This has led researchers to test the beneficial effects of certain compounds found in fruits and vegetables on blood pressure levels.

Nitrate

Nitrate is a compound found in beetroot and dark leafy greens like spinach and arugula (21).

When you consume nitrate, your body converts it to nitric oxide, which in turn causes blood vessels to relax and dilate, lowering blood pressure.

Several studies have shown dietary nitrate may help lower blood pressure by increasing the production of nitric oxide (22, 23).

In fact, one review of 22 studies found that taking nitrate supplements significantly reduced systolic and diastolic blood pressure in older adults (24).

What’s more, another review of 43 studies found participants’ systolic and diastolic blood pressures decreased by an average of 3.55 and 1.32 mmHg, respectively, after they drank beetroot juice (25).

Flavonoids

Flavonoids are compounds found in almost all fruits and vegetables, which have powerful antioxidant properties (26).

Some studies have found that increased intake of flavonoids could be linked to a reduced risk of high blood pressure (27, 28).

Scientists believe flavonoids not only increase production of nitric oxide but also decrease its breakdown, promoting higher levels overall.

However, a few studies have turned up conflicting results on its potential benefits.

For instance, one review of 15 studies found that consumption of flavonoid-rich fruits had no significant effect on blood pressure levels in adults (29).

Vegetables and fruits contain several compounds, such as nitrate and flavonoids, that may help keep blood pressure under control by increasing nitric oxide levels.

4. Boosts exercise performance

Nitric oxide is involved in many cell processes, including the widening of the blood vessels, or vasodilation. Wider blood vessels help increase the delivery of nutrients and oxygen to working muscles during exercise, thus enhancing exercise performance.

This has made nitric oxide supplements popular among athletes and recreational gym-goers.

These supplements often contain several ingredients that are said to increase nitric oxide, such as nitrate or the amino acids L-arginine and L-citrulline.

In many analyses, nitrate has been shown to improve exercise performance in cyclists, runners, swimmers, and even kayakers (30, 31, 32).

On the other hand, L-arginine has not proven to be effective for improving exercise performance in many studies (33, 34).

According to one older study, this may be because much of the L-arginine that is ingested is metabolized or broken down before it gets a chance to reach the bloodstream (35).

Supplements intended to increase nitric oxide are commonly promoted as performance enhancers. While the performance-enhancing benefits of L-arginine are minimal, nitrate and L-citrulline may be worthwhile.

5. May help manage type 2 diabetes

Nitric oxide production may be reduced in people with type 2 diabetes (36).

This leads to poor blood vessel health, which can lead to conditions like high blood pressure, kidney disease, and heart disease over time.

Therefore, supplements that increase nitric oxide may have important implications for diabetes treatment and disease prevention.

One review of 10 studies found that supplementing with L-arginine could significantly reduce insulin levels in people without diabetes (37).

Another 2012 study in 144 people looked at the effects of L-arginine on preventing or delaying the progression of type 2 diabetes (38).

While L-arginine did not prevent people from developing diabetes, it did increase insulin sensitivity and improve blood sugar control (38).

However, other research has found no effect of L-arginine on fasting blood sugar levels and blood sugar control in people with diabetes (39).

Therefore, until more research is available, it is premature to recommend taking L-arginine supplements to treat or manage diabetes.

People with diabetes have impaired nitric oxide production, which can lead to harmful health effects. L-arginine has been shown to reduce insulin levels and slow the progression of diabetes, but more research is needed before it can be recommended.

Side effects

Nitric oxide supplements are generally safe when taken in appropriate amounts (13, 40).

However, there are some side effects to be aware of.

According to some older research, L-arginine taken in doses above 10 g can cause stomach discomfort and diarrhea (41).

Beetroot juice supplements can also turn your urine and stool a dark red color. This is a common but harmless side effect (42).

Before taking any supplements to increase nitric oxide, consult a doctor or dietitian.

Nitric oxide supplements are generally considered safe. However, there are some side effects to be aware of, including potential stomach discomfort and diarrhea, as well as dark red stool and urine.

The bottom line

Nitric oxide is a molecule that plays many important roles in human health.

Many supplements are claimed to increase nitric oxide in the body and provide impressive benefits for health and performance.

They usually contain ingredients like nitrate or the amino acids L-citrulline and L-arginine.

However, other supplements, such as French maritime pine bark extract, have also been shown to increase or maintain nitric oxide levels.