Does watermelon help erectile dysfunction?
Watermelon is a real dietary source of L-citrulline, but its concentration (150-350mg per cup) falls well below the 1.5-6g daily doses used in trials showing benefit.
The short answer
Watermelon flesh naturally contains L-citrulline, the amino acid the body converts into L-arginine and then nitric oxide -- the vessel-relaxing signal behind erectile function and the mechanism preserved by PDE5 inhibitor drugs. Trials showing benefit for mild ED and blood pressure used 1.5-6g of L-citrulline per day, while a cup of watermelon delivers roughly 150-350mg, meaning matching a trial dose through fruit alone would mean several cups a day. Watermelon rind is 2-3x more concentrated than the flesh, which narrows but doesn't close that gap. A folk reputation as a mild aphrodisiac and cooling tonic long predates the citrulline research itself.