April 2, 2008

The Mythical Daily Water Requirement

There's no evidence that humans actually need the oft-cited "eight-glasses-per-day" of water. Karen Hopkin reports.

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Podcast Transcript: Somewhere along the line you’ve probably heard that you should drink eight glasses of water a day. It’s supposed to make your skin supple, keep your organs flush and help you avoid overeating. Now doctors from the University of Pennsylvania say that’s hogwash. After exploring the health effects of hydration, they conclude that the purported benefits of drinking lots of water are not backed by any solid evidence—or liquid evidence, either. The physicians present their findings in the June issue of the Journal of the American Society of Nephrology.

Okay, humans can’t last more than a few days without water. But very little research has been done to assess just how much water a healthy individual needs. So the Pennsylvania docs scanned the literature. They discovered that drinking water does help the kidneys clear out salt and such. But those studies don’t suggest any sort of clinical benefit. There are no studies that show that chugging H2O will curb your appetite. Ditto for drinking water to enhance your skin tone. In fact, no studies indicate that people should drink eight glasses of water a day. Where that number came from no one seems to know. But in the end, it turns out to be all wet.

—Karen Hopkin

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