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A piece of sweet, sweet juicy watermelon is a crown for fourth of July and a meal means that researchers have effects similar to Viagra – but do not necessarily expect to keep the fireworks all night.

Watermelons contain an ingredient called citrulline that can trigger production of a compound that helps relax blood vessels of the body, similar to what happens when a man takes Viagra, said scientists in Texas, a leading producer of seeds of the variety. Found in meat and rind of watermelons, citrulline reacts with enzymes in the body when consumed in large quantities and is converted into arginine, an amino acid that benefits the heart and the circulatory and immune system.

“Arginine stimulates nitric oxide, which relaxes blood vessels, the same basis as Viagra to treat erectile dysfunction and even prevent it,” said Bhimu Patil, a researcher and director of the Texas A & M Fruit and Vegetable Improvement Center. “Watermelon may not be as organ specific as Viagra, but it is a great way to relax blood vessels without the side effects of drugs.”

Todd Wehner, who studies watermelon breeding at the University of North Carolina State, said anyone taking Viagra should not expect the same result from watermelon. “It seems that this is an effect that would be interesting but not a substitute for medical treatment,” Wehner said. Nitric oxide can also help with angina pectoris, hypertension and other cardiovascular problems, according to the study, which was paid by the U.S. Department of Agriculture.

More citrulline – about 60 percent – is found in the rind of the watermelon in the flesh, Patil said, but may vary. But scientists may be able to find ways to increase the concentration in the flesh, he said. Citrulline is found in all colors of watermelon and is highest in the yellow flesh types, said Penelope Perkins-Veazie, a USDA researcher in Lane, Oklahoma. She said Patil research is valid, but with a caveat: One would have to eat about Six Cups of Watermelon to get enough citrulline to boost the body arginine level.

– “The problem you have when you eat a lot of watermelon is that they tend to run to the bathroom more.”
Watermelon is a diuretic and a homeopathic treatment for kidney patients before extended dialysis.

– Another problem is the amount of sugar that the amount of water released into the bloodstream – a jolt that could cause cramping.
Patil said he would like to do future studies on how to reduce the sugar content in watermelon.

The relationship between citrulline and arginine might also prove useful for those who are obese or suffer from type 2 diabetes. The beneficial effects – among them the ability to relax blood vessels, like Viagra – are beginning to be revealed in research.