We've all heard the advice: To stay healthy you need to drink 8 glasses of water a day. But is this recommendation fact or fiction?

Researchers from the University of Pennsylvania combed the medical literature for studies on water, and it turns out, there aren't very many.

They found no convincing evidence that humans need 64 ounces of the water each day.

Dr. Stanley Goldfarb, a kidney doctor, who co-authored this study, says there's no evidence drinking extra will improve your skin, keep your organs healthy or help you lose weight. Sorry about that!

So why does drinking lots of water seem to be such a good thing to do?

"It's easy and it's apparently safe and it represents a kind of advice that apparently doesn't have a downside, that it's become a recommendation, and then, I think has actually become a burden on many people," Goldfarb said.

A lack of water doesn't seem to trigger headaches, either.

The bottom line, unless you're sweating profusely because of the heat or a strenuous work out, drink when you're thirsty. You'll get all the water your body needs each day from what your regular diet.

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Advice on water doesn't hold water