Nitric oxide is produced by nearly every type of cell in the human body and is one of the most important compounds for blood vessel health. NO causes a widening of blood vessels and triggers the release of certain hormones, like human growth hormone and insulin.
Since it’s a vasodilator (that is, it relaxes the blood vessels, causing them to widen), nitric oxide increases blood flow and lowers blood pressure.
Nitric oxide supplements are a type of supplement that will usually include L-arginine and/or L-citrulline. Numerous studies and clinical trials pertaining to nitric oxide supplements have been conducted to determine what benefits they may provide.
This article will look at how nitric oxide works in the body and review some of the many health benefits associated with nitric oxide supplementation, as well as any potential risks.
How Nitric Oxide Supplements Work
Supplements that increase the levels of nitric oxide in the body are some of the most popular types of supplements on the market.
While these supplements don’t contain actual nitric oxide, they do contain ingredients that your body can utilize to produce more NO. These products have been shown to provide many benefits for health and athletic performance.
Two of the most commonly used ingredients found in nitric oxide supplements are L-arginine and L-citrulline.
L-arginine is an amino acid that is naturally found in red meat, poultry, fish, and dairy products. It is typically manufactured as a pill, powder, or cream.
L-citrulline, also an amino acid, naturally occurs in meats, nuts, legumes, and watermelon. L-citrulline supplements also are made available in either pill or powder form.
The average person normally consumes about 5 grams of L-arginine per day, and this gets converted into nitric oxide by the body for various uses.
As stated earlier, it’s thought that nitric oxide relaxes and widens blood vessels. Certain medications used to treat erectile dysfunction (like Viagra) use the nitric oxide pathway to encourage blood vessels to widen and increase blood flow to the penis in order to enhance erection quality.
For these reasons, nitric oxide supplements are taken to improve blood flow in the body to enhance sports performance, speed up healing, and boost heart health, among many other possible benefits.
Benefits of Using Nitric Oxide Supplements
1. Increases Exercise Performance
In addition to many other bodily processes, nitric oxide promotes vasodilation, or widening of the blood vessels. Wider blood vessels boost the amount of nutrients and oxygen being delivered to working muscles during exercise, resulting in enhanced athletic performance.
For this reason, nitric oxide supplements are extremely popular among athletes and bodybuilders.
Also known as preworkout supplements, these products usually contain several compounds that are thought to increase nitric oxide, including the amino acids L-arginine and L-citrulline, as well as nitrate.
There have been many studies demonstrating that nitrate can enhance exercise performance in runners, cyclists, swimmers and even kayakers (1).
However, L-arginine may not be quite as effective at improving exercise performance. It’s theorized that much of the L-arginine that is consumed is broken down and metabolized in the digestive tract before reaching the bloodstream, whereas L-citrulline isn’t (2).
Because of this, L-citrulline may be more effective than L-arginine at boosting nitric oxide levels, and therefore exercise performance.
2. Helps Reduce Muscle Soreness
Muscle soreness can occur after vigorous exercise or when performing exercise that the body is unaccustomed to. This conditinon is often referred to as “delayed-onset muscle soreness”, since it usually peaks from 24–72 hours after exercise.
One type of L-citrulline (called citrulline malate) not only raises production of nitric oxide, but also reduces muscle soreness.
One study involved 41 individuals who were randomly given either 8 grams of citrulline malate or a placebo, one hour prior to performing as many bench press reps as possible.
The participants who received citrulline malate experienced 40% less muscle soreness 24 and 48 hours post-exercise, compared to those receiving a placebo (3).
Citrulline malate raises nitric oxide production, which boosts blood flow to working muscles. As a result, citrulline malate is believed to increase delivery of nutrients and remove waste by-products associated with muscle fatigue, like ammonia and lactate (4).
Even so, a separate study observing the effects of citrulline after performing leg exercises showed that citrulline malate did not help reduce muscle soreness.
However, the participants in this study only took 6 grams of citrulline malate, where those in the previous study took 8 grams (5).
Therefore, citrulline malate’s ability of to reduce muscle soreness could be dependent upon the dose and type of exercise. But more research will be necessary.
3. Lowers Blood Pressure
High blood pressure is a condition where the force of blood pushing against the arterial walls is consistently excessive. Eventually, this elevation in blood pressure can result in any number of health conditions, like heart disease and kidney disease.
It’s believed that individuals with high blood pressure are unable to fully use the available nitric oxide in their bodies (6).
Studies show that a fiber-rich diet high in fruits and vegetables reduces blood pressure, and in turn, lowers the likelihood of disease (7). This discovery led researchers to examine the beneficial properties of two compounds found in fruits and vegetables, flavonoids and nitrate, and their effects on blood pressure levels.
Flavonoids are found in nearly all fruits and vegetables and are considered powerful antioxidants. Flavonoid extracts have also demonstrated an ability to improve blood pressure (8).
Researchers conclude that flavonoids not only increase nitric oxide levels, but also inhibit its breakdown, increasing overall NO levels in the body.
Nitrate is a compound that occurs naturally in beetroot and dark leafy green vegetables like spinach and kale. After consuming nitrate, it gets converted into nitric oxide, causing the blood vessels to relax and dilate, resulting in lower blood pressure.
There’s plenty of research that shows how nitrate can help lower blood pressure by boosting nitric oxide levels.
One review of several research studies looked to determine the effects of nitrate supplements on blood pressure in adults. Out of thirteen studies reviewed, six saw drmatic reductions in both systolic and diastolic blood pressure after participants used nitrate supplements (9).
On top of that, an even bigger review of over 40 research studies showed that the systolic and diastolic blood pressure of participants was reduced by an average of 3.55 and 1.32 mm Hg respectively after using nitrate supplements (10).
4. Treatment For Erectile Dysfunction
Erectile dysfunction, or ED, is the inability to achieve or maintain an erection. As noted before, L-citrulline is an amino acid that increases the production of nitric oxide and may help treat erectile dysfunction.
Nitric oxide allows for the penile muscles to relax. As a result, the chambers inside the penis fill with blood causing the penis to become erect.
L-citrulline was shown to improve erection quality in a study involving 12 men with mild erectile dysfunction. The researchers found that while L-citrulline was not as effective as prescription ED drugs like Viagra, it did prove to be safe and well tolerated (11).
Two additional supplements that boost nitric oxide have also been shown to help treat erectile dysfunction when taken together: L-arginine and Pycnogenol, an extract of French maritime pine bark.
There’s quite a lot of research showing that a combination of L-arginine and Pycnogenol can dramatically (and safely) improve sexual function in men with ED (12).
5. Helps Control Type 2 Diabetes
Individuals with type 2 diabetes tend to have an impaired ability to produce nitric oxide. This can result in poor blood vessel health, eventually leading to conditions like high blood pressure, heart disease and kidney disease.
As such, supplements that can boost nitric oxide levels can offer significant potential for diabetes treatment and prevention.
Research shows that when individuals with type 2 diabetes take L-arginine, their nitric oxide levels increase, leading to higher insulin sensitivity and greater blood sugar control.
One study involving over 140 participants examined whether or not L-arginine could help prevent or delay the progression of type 2 diabetes. Although L-arginine didn’t prevent the development of diabetes, it did boost insulin sensitivity and better regulate blood sugar (13).
However, further research is necessary to fully understand the benefits that L-arginine supplements may offer for the treatment of diabetes.
When taken in appropriate doses, Nitric oxide supplements are generally considered safe. That said, certain side effects are possible.
Large doses of L-arginine of more than 10 grams may cause diarrhea and gastrointestinal distress (14).
Taking beetroot juice supplements can cause a dark red coloration of the urine and stool. This is actually a common side effect, but quite harmless.
As always, be sure to talk with your health care provider prior to taking any supplements to increase nitric oxide.
The Bottom Line
Nitric oxide is crucial to many aspects to maintaining optimal health. There are numerous supplements available which increase nitric oxide levels in the body and offer amazing benefits for athletic performance and overall health.
These products typically contain ingredients such as nitrate and/or the amino acids L-arginine and L-citrulline. Additionally, other supplements, like Pycnogenol, also show an ability to increase or maintain nitric oxide levels.