Scientists with the Texas A&M's Fruit and Vegetable Improvement Center have found that an organic compound found in watermelon acts somewhat similar to sildenafil citrate, better known under its brand name: Viagra.

The substance, citrulline, triggers upon consumption the production of a compound that helps relax the body's blood vessels, arginine, which acts much like Viagra does, but is not as powerful or organ-specific. However, the natural compound found in watermelon also lacks the significant side effects and risks associated with Viagra.

Arginine can also help with angina, high blood pressure and other cardiovascular problems, said researchers who were working under a grant from the U.S. Department of Agriculture. The problem with watermelon is that it is a known diuretic, causing people to go to the bathroom to discard fluids quite often.

Also, around six cups of watermelon are needed for an effect you can... feel. One cup provides around 50 calories. Apart from citrulline, watermelon also provides the body a wide range of useful compounds, such as vitamin C and vitamin A, vitamin B6 and vitamin B1, as well as the minerals potassium and magnesium.

It appears that most citrulline is found in watermelon that has a yellow colored flesh.

Watermelon originates from southern Africa, apparently from around the Kalahari desert area. There is evidence of its cultivation in the Nile Valley from at least as early as the second millennium BC. The fruit hit Europe in the 13th century AD, three centuries after reaching China.