Citrulline
L-Citrulline, or simply just citrulline, is a nonessential amino acid. It is efficiently turned into L-arginine in the kidneys after supplementation, which makes it a good choice for increasing nitric oxide synthesis in the body.
Citrulline is most often used for
Last Updated:May 19, 2023
Citrulline is one of the three dietary amino acids in the urea cycle (the other two are L-arginine and L-ornithine). Taking citrulline increases plasma levels of arginine and improves the ammonia recycling process and nitric oxide metabolism. Consequently, citrulline may be useful in situations in which nitric oxide is relevant, such as athletic performance, vascular health, and erectile dysfunction. There are very few foods that have useful amounts of citrulline, but watermelon is a notable exception. The two most common forms of citrulline are L-citrulline and citrulline malate.
There is limited evidence that citrulline supplementation can reduce ratings of perceived exertion, decrease muscle soreness, and increase power output and total repetitions performed in resistance training.[1][2][3] More research is needed to determine whether different supplement dosages, different formulations, or longer periods of ingestion can further improve exercise performance.
A considerable amount of research suggests that supplementation with citrulline mildly reduces blood pressure.[4] More research is needed on citrulline’s potential effects for erectile dysfunction, but a small amount of research suggests a beneficial effect.[5]
Although the safety of long-term supplementation with high doses of citrulline warrants further investigation, research to date suggests that it is well tolerated in most individuals. Unlike arginine and ornithine, high doses of citrulline don't seem to result in gastrointestinal distress.[2]
Citrulline supplementation increases the body’s arginine levels. Because arginine is the main substrate for the synthesis of nitric oxide, citrulline ingestion can indirectly increase nitric oxide production. In turn, given the role of nitric oxide in vasodilation, mitochondrial respiration, calcium handling, and glucose uptake, greater amounts of nitric oxide can theoretically improve circulatory health and muscle function and reduce fatigue.
- L-Citrulline
- Stimol (Brand Name)
- citrulline malate
To supplement L-citrulline for circulatory health or to alleviate erectile dysfunction, take 2,000 mg of citrulline, three times a day with meals, for a total daily dose of 6,000 mg. L-citrulline does not need to be taken with meals, however.
To supplement for circulatory health with a citrulline malate supplement, take 1.76 g of citrulline malate for every 1 gram of citrulline you would normally take.
To supplement L-citrulline to enhance sports performance, take 6,000 – 8,000 mg of citrulline malate about an hour before exercise. On days that you don't exercise, it can be broken up into smaller doses.