Viagra Like Effects from Watermelon

July 1, 2008 — Men hoping for some fireworks in their love life this Fourth of July may want to skip the burgers and beer at the barbecue and eat plenty of watermelon.  But according to recent studies, the juicy fruit may be better suited for Valentine’s Day. That’s because scientists say watermelon has ingredients that deliver Viagra-like effects to the body’s blood vessels and may even increase libido.  Watermelon may be a natural Viagra because the popular summer fruit is  in an amino acid called citrulline, which relaxes and dilates blood vessels much like Viagra and other drugs meant to treat erectile dysfunction (ED).

“We have known that watermelon has citrulline,” says Bhimu Patil, PHD, director of the Fruit and Vegetable Improvement Center at Texas A&M University, College Station.  How could watermelon be a natural Viagra? The amino acid citrulline is converted into the amino acid arginine, Patil says. “This is a precursor for nitric oxide, and the nitric oxide will help in blood vessel dilation.”

“The citrulline-arginine relationship helps heart health, the immune system and may prove to be very helpful for those who suffer from obesity and type 2 diabetes,” said Patil. “Arginine boosts nitric oxide, which relaxes blood vessels, the same basic effect that Viagra has, to treat erectile dysfunction and maybe even prevent it.”

While there are many psychological and physiological problems that can cause impotence, extra nitric oxide could help those who need increased blood flow, which would also help treat angina, high blood pressure and other cardiovascular problems.

On hearing about the Texas finding, Irwin Goldstein, MD, editor-in-chief of The Journal of Sexual Medicine, was underwhelmed. Suggesting a man feast on watermelon to boost performance, he says, “would be the equivalent of someone dropping a beer bottle in Minneapolis, where the Mississippi River starts, and hoping to see it make an impact on someone in New Orleans.”

“To say that watermelon is Viagra-like is sort of fun,” says Goldstein. “But to even vaguely hope that eating watermelon will alleviate ED is misleading.”

“The vast majority of Americans produce enough arginine,” adds Goldstein, medical director of Alvarado Hospital Medical Center, San Diego, and clinical professor of surgery, University of California San Diego School of Medicine. “Men with ED are not deficient in arginine.”

Though arginine is required to make nitric oxide, and nitric oxide is required to dilate blood vessels and have an erection, “that doesn’t mean eating something that is rich in citrulline will make enough arginine that it will lead to better penile erections,” Goldstein says.

“Watermelon may not be as organ specific as Viagra,” Patil said, “but it’s a great way to relax blood vessels without any drug side-effects.”

The benefits of watermelon don’t end there, he said. Arginine also helps the urea cycle by removing ammonia and other toxic compounds from our bodies.

Citrulline, the precursor to arginine, is found in higher concentrations in the rind of watermelons than the flesh. As the rind is not commonly eaten, two of Patil’s fellow scientists, drs. Steve King and Hae Jeen Bang, are working to breed new varieties with higher concentrations in the flesh.

In addition to the research by Texas A&M, watermelon’s phyto-nutrients are being studied by the U.S. Department of Agriculture’s Agricultural Research Service in Lane, Oklahoma.

As an added bonus, these studies have also shown that deep red varieties of watermelon have displaced the tomato as the lycopene king, Patil said. Almost 92 percent of watermelon is water, but the remaining 8 percent is loaded with lycopene, an anti-oxidant that protects the human heart, prostate and skin health.

“Lycopene, which is also found in red grapefruit, was historically thought to exist only in tomatoes,” he said. “But now we know that it’s found in higher concentrations in red watermelon varieties.”

Lycopene, however, is fat-soluble, meaning that it needs certain fats in the blood for better absorption by the body, Patil said.

“Previous tests have shown that lycopene is much better absorbed from tomatoes when mixed in a salad with oily vegetables like avocado or spinach,” Patil said. “That would also apply to the lycopene from watermelon, but I realize mixing watermelon with spinach or avocadoes is a very hard sell.”

No studies have been conducted to determine the timing of the consumption of oily vegetables to improve lycopene absorption, he said.

“One final bit of advice for those Fourth of July watermelons you buy,” Patil said. “They store much better uncut if you leave them at room temperature. Lycopene levels can be maintained even as it sits on your kitchen floor. But once you cut it, refrigerate. And enjoy.”

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• Nitric oxide as a mediator of relaxation of the corpus cavernosum in response to nonadrenergic, noncholinergic neurotransmission.
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• Overexpression of arginase in the aged mouse penis impairs erectile function and decreases eNOS activity: influence of in vivo gene therapy of anti-arginase.
• Molecular mechanisms of the effects of sildenafil (VIAGRA).