L-citrulline is a nonessential amino acid that improves the flow of blood throughout the body. It also boosts the reserve of nutrients the body requires to manufacture particular proteins. Naturally-occurring in the urea cycle, L-citrulline can be taken as a nutritional supplement to aid such conditions as mental fatigue, physical fatigue, Alzheimer's disease, heart disease, and sexual dysfunction. It can also enhance the benefits of exercising and bodybuilding.
After it is produced in the human body, L-citrulline rids the body of the toxic ammonia contained in urea. L-citrulline is then converted to L-arginine, one of the most frequently occurring amino acids. From there it transforms into nitric oxide, a gas manufactured in the body that aids in vascular health and detoxification of the liver.
L-citrulline is not strictly unique to the human body, however. It can also be found in several foods, such as meat, fish, dairy, beans, and eggs. It is most predominant, though, in watermelon. In fact, the word "citrulline" comes from the Latin word "citrullus," meaning watermelon. In 1930, L-citrulline was isolated from watermelon for the first time and identified as a key factor in healthy blood flow.
Taken as a a nutritional supplement, L-citrulline has been shown to expand blood vessels, which encourages less restrictive blood flow. This freer blood flow can aid in treating many medical conditions, from the mental fogginess of dementia to the frustrations of sexual dysfunction. L-citrulline is also frequently given to children before and after heart surgery to promote healthy blood flow to and from the heart. L-arginine, the direct by-product of L-citrulline, helps wounds heal quicker and performs an important function in healthy cell division.
Since L-citrulline helps keep the blood moving, energy levels naturally rise and endurance levels tend to heighten. This has made it a popular choice among bodybuilders and exercise enthusiasts. Research also suggests L-citrulline can encourage resistance to muscle fatigue.
A typical dosage of L-citrulline is 1.25 teaspoons (0.2 ounces) twice daily. It is widely available in capsule varieties as well. Consuming the liquid form, however, offers faster absorption rates than the capsule form.
There are few side effects to taking L-citrulline as a dietary supplement. Those with kidney problems and those with a past sensitivity to this amino acid should not take it as a supplement. It is also not recommended for children under 12 years of age unless advised by a doctor.