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Don't believe the hype: watermelon isn't a natural Viagra

Steven Depolo

Summer is just around the corner, which mean the time is ripe once again for headlines proclaiming that watermelon is "nature's Viagra."

The idea: eating watermelon or drinking its juice can help treat erectile dysfunction

The idea seems to have been planted by a 2008 press release put out by Texas A&M University. In it, professor Bhimu Patil describes how he and other researchers had been studying the many nutritional benefits of watermelon — including the fact that one of its nutrients, citrulline, indirectly causes blood vessels to dilate, the same mechanism through which Viagra works.

As a result, the press release was titled "Watermelon May Have Viagra-effect," and it garnered all sorts of coverage, introducing an idea that would surface over and over on the web.

The evidence for it

There's not much. A 2011 Italian study looked at the effect of citrulline supplements on men with mild erectile dysfunction. Over the course of a month taking these pills, half of the men reported slight improvements in their erections.

The researchers noted that, inside the body, citrulline is converted into another chemical, arginine, which is known to increase blood flow by relaxing your blood vessels.

The evidence against it

No one's rigorously tested whether eating lots of watermelon would have the same effect as concentrated citrulline supplements — but basic logic tells us that there's absolutely no way it could be a "natural Viagra," press releases be damned.

When WebMD responded to the idea back in 2008, the editor-in-chief of The Journal of Sexual Medicine was quoted as saying that "to even vaguely hope that eating watermelon will alleviate ED is misleading."

There are two problems with the idea. One is that it'd be really difficult to eat enough watermelon to substantially boost your body's levels of arginine, the product of citrulline that actually aids in blood flow. A 2007 study that had people drinking 55 ounces of watermelon juice per day saw their blood levels of arginine increase by just 22 percent, a level that'd be doubtful to enhance sexual performance.

But the bigger problem is that even if you increased arginine levels enough, you still probably wouldn't treat most cases of erectile dysfunction, because the vast majority of men with ED already have enough arginine in their bodies.

Yes, arginine is involved in increasing blood flow, but it does so all throughout the body. Producing an erection is a particularly complex process, and Viagra helps men do it by raising levels of a chemical called cGMP in penis tissue specifically. Just increasing the amount of arginine in your blood won't do this — the reason why in the original press release, Patil cautioned that "Watermelon may not be as organ specific as Viagra."

Eating tons of it in hopes of treating erectile dysfunction will accomplish exactly one thing: it'll have you peeing a lot, since the melon is a diuretic and is about 92 percent water.