Watermelon contains an amino acid that increases blood flow by producing Nitric Oxide. This amino acid called citrulline is being used as a supplement for increasing blood flow and lowering blood pressure. Bodybuilders feel “the pump” when they take citrulline.
ScienceDaily (July 1, 2008) — A cold slice of watermelon has long been a Fourth of July holiday staple. 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.