Watermelon May Have Viagra-Like Effect (2008)

There is a chemical found in grapefruit juice which when consuming around a litre of the juice, slows up the metabolism in the liver of the chemical that makes Viagra work.

This is why its advised to avoid grapefruit juice with some prescription drugs, because it causes the prescription drugs to hang around in the body for longer and in higher quantities which in turn cause health problems.

1 litre of grapefruit juice could make Viagre work for about 8 hours which is dangerous and amputation territory.