WebMD Medical News
Brunilda Nazario, MD
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 may be a natural Viagra, says a researcher.
That's because the popular summer fruit is richer than experts believed 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. Until recently, he tells WebMD, scientists thought
most of the citrulline was in the watermelon rind. "Watermelon has more
citrulline in the edible part than previously believed," he says.
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
So, the burning question: How much watermelon does it take?
"That is a good question," Patil says. Unfortunately, "I don't have an
answer for that."
He does know that a typical 4-ounce serving of watermelon (about 10
watermelon balls) has about 150 milligrams of citrulline. But he can't say how
much citrulline is needed to have Viagra-like effects.
He's hopeful that someone will pick up on his research and study the fruit's
effect on penile erections.
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
"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.
Goldstein has served as a consultant for many companies that make ED
Calling watermelon a natural Viagra is "clearly premature," says Roger
Clemens, DrPH, adjunct professor of pharmacology and pharmaceutical sciences,
University of Southern California, Los Angeles, and a spokesman for the
Institute of Food Technologists.
Clemens studied the amino acid arginine himself, researching a supplement to
improve vascular flow for patients with hardening of the arteries or atherosclerosis. He has since
abandoned that line of research, he says.
It can require a lot of watermelon to boost blood levels of arginine, he
adds. In a study published in 2007 in Nutrition, he says, volunteers who
drank three 8-ounce glasses of watermelon juice daily for three weeks boosted
their arginine levels by 11%.
Watermelon is low in calories and provides potassium and the phytonutrients
lycopene and beta-carotene, in addition to the citrulline.
Clemens' advice on watermelon and the Fourth of July? "Put salt on it and
Just don't expect fireworks anywhere but in the sky.
SOURCES:Bhimu Patil, PhD, director of Texas A&M University Fruit and Vegetable
Improvement Center, College Station.Roger Clemens, DrPH, adjunct professor, pharmacology and pharmaceutical
sciences, University of Southern California, Los Angeles; spokesman, Institute
of Food Technologists.Irwin Goldstein, MD, editor-in-chief, Journal of Sexual Medicine;
medical director, Alvarado Hospital Medical Center; clinical professor of
surgery, University of California San Diego.Clevidence, B.A. Nutrition, March 2007; vol 23: pp 261-266.
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