Increase nitric oxide in the body make up one of the most popular supplement categories today.
Nitric oxide is produced by nearly every type of cell in the human body and one of the most important molecules for blood vessel health.
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.
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.
Erectile dysfunction (ED) is the inability to achieve or maintain an erection firm enough for sex .
L-citrulline is an amino acid that may help treat erectile dysfunction by increasing the production of nitric oxide.
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.
In one study, L-citrulline was found to improve erection hardness in 12 men with mild erectile dysfunction.
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.
Two other nitric-oxide-boosting supplements have been shown to treat erectile dysfunction — the amino acid L-arginine and Pycnogenol, a plant extract from the pine tree.
In several studies, a combination of L-arginine and Pycnogenol significantly improved sexual function in men with ED.
When taken together, L-arginine and Pycnogenol also appear safe.
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.
This soreness is referred to as delayed-onset muscle soreness and usually feels the strongest 24–72 hours after exercise.
In one study, 41 people were randomized to receive either 8 grams of citrulline malate or a placebo one hour before performing as many repetitions as possible on a flat barbell bench press.
Those given citrulline malate reported 40% less muscle soreness at 24 and 48 hours after the exercise, compared to those who took the placebo.
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.
However, a later study on the effects of citrulline after leg exercises did not find citrulline malate helpful for the treatment of muscle soreness.
One explanation for this difference in findings is that the people in the leg exercise study were given 6 grams of citrulline malate, which is 2 grams less than the previous study.
Therefore, the ability of citrulline malate to decrease muscle soreness may depend on the dose and exercise. However, more research on this is needed.
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.
On the other hand, L-arginine has not proven to be effective for improving exercise performance in many studies.
This is likely because most of the L-arginine that is ingested is metabolized or broken down before it gets a chance to reach the bloodstream, whereas L-citrulline is not.
For this reason, L-citrulline is more effective than L-arginine at increasing nitric oxide and therefore exercise performance.
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 Pycnogenol, have also been shown to increase or maintain nitric oxide levels.