Watermelon is one of the richest sources of citrulline. Citrulline is a nonessential amino acid and antioxidant that is converted to another amino acid called arginine by special enzymes. Arginine has a key role in cell division, wound healing, and the removal of ammonia from the body. A watermelon's quantity of citrulline varies by each fruit's qualities.
There are over 50 varieties of watermelons that vary in sweetness, shape and flesh color, and texture. They may also be seeded or seedless. Citrulline is found in all parts of the watermelon, including seeds, flesh and rind. When watermelons were compared by flesh color, red-fleshed melons had less citrulline in their flesh or rind than orange or yellow fleshed fruit did, according to a study in the “Journal of Chromatography A.” However, the highest level of citrulline was found in the seedless watermelon types called Hazera SW1 and Solid Gold and the seeded Summer Gold watermelon varieties. This study also found that the watermelon rind generally contains citrulline in high quantities.
Watermelons have special compounds called phytonutrients. which include lycopene, beta carotene and citrulline. They can improve sexual stamina and erectile dysfunction. Lycopene plays a role in protecting the prostate. The October 2013 issue of "The Journal of Sexual Medicine" reports that citrulline supplementation improves erectile dysfunction. It relaxes the blood vessels, but it does not target specific organs like prescription medication for erectile dysfunction does. More research needs to be done to confirm the role of citrulline in improving sexual performance.
The combination of citrulline and arginine might provide more benefits to the heart and immune system. It may also be useful for diabetes and sickle cell disease treatments. Arginine detoxifies by removing ammonia and other toxins from the body. It also boosts nitric oxide, which improves blood flow and thus might help treat high blood pressure, angina and other cardiovascular problems. Citrulline is abundantly available in watermelons and readily usable by the body. Concentrated watermelon extract can increase levels of plasma arginine, based on a study in the journal “Nutrition,” in which research participants consumed varying amounts of watermelon juice.
Although watermelon's nutritive substances may have medicinal value, research is ongoing about using natural substances of citrulline and arginine found in watermelon in the treatment of health. Never overconsume a food or supplement based on preliminary research findings or proven research to improve a health condition. Speak to your doctor or a dietitian about including watermelon in a healthy diet.