Why Take the Blue Pile While Watermelon Have the Same Effect?

Citrulline is the ingredient in watermelon that has an effect similar to Viagra - relax blood vessels - because it changes into arginine in reaction with enzymes of the body.

Watermelon from shnnn on flickr.
It is also said that it can:

reduces risk of heart disease,
decreases blood pressure,
improves circulatory and immune function

Those researches always make me [...]