Researchers at Texas A&M have found that watermelons are rich in an amino acid that relaxes and dilates blood vessels, much like Viagra and other erectile-dysfunction drugs.

The amino acid, citrulline, was known to be present in watermelons but not in the concentration that researchers have discovered. Citrulline is converted into the amino acid arginine, said Bhimu Patil, Ph.D., director of the Fruit and Vegetable Improvement Center at Texas A&M University, College Station. "This is a precursor for nitric oxide, and the nitric oxide will help in blood vessel dilation."

"We have known that watermelon has citrulline," said Patil, pointing out that previous research indicated that citrulline was thought to be in the usually discarded white watermelon rind. "Watermelon has more citrulline in the edible part than previously believed." A typical 4-ounce serving of watermelon has about 150 milligrams of citrulline, Patil said, but the amount of citrulline needed to facilitate an erection requires further study.

Dr. Irwin Goldstein, editor-in-chief of The Journal of Sexual Medicine, told reporters that suggesting a man feast on watermelon to boost performance "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," Goldstein said. "But to even vaguely hope that eating watermelon will alleviate ED is misleading."

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 said.

Then again ... sometimes a watermelon is just a watermelon.