Want the Viagra effect without taking a pill? Try eating a watermelon

slice of watermelon has libido-boosting effects similar to the Viagra, researchers have discovered.

An ingredient called citrulline found in the flesh and rind of the fruit can help relax the body's blood vessels, just like the erectile-dysfunction drug, they said.

When consumed in large enough amounts, citrulline is turned into a substance called arginine which benefits the heart and the circulatory and immune systems.

'Arginine boosts nitric oxide, which relaxes blood vessels, the same basic effect that Viagra has, to treat erectile dysfunction and maybe even prevent it,' said Bhimu Patil, a Texas researcher.

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

But other scientists warned that further development was needed before the findings made at Texas A&M's research centre bore fruit.

US government agriculture expert Penelope Perkins-Veazie said you would need to eat about 4lb of watermelon - which is a diuretic - to get enough citrulline to boost the body's arginine level.

She said: 'The problem you have when you eat a lot of watermelon is you tend to run to the bathroom more.'

She added that the sugar from the watermelon could cause cramping.

Mr Patil conceded that scientists would have to find ways to boost the concentrations of citrulline in the watermelon flesh. He also hopes to carry out studies on how to reduce the sugar content.