Eight Glasses of Water a Day Is ‘Nonsense’

Are you one of millions of Americans who looks down with pride at the powerful stream of colorless, translucent fluid flowing out of your body every time your empty your bladder? Who takes great personal satisfaction in knowing you've downed enough bottled water in a single day to satisfy the hydration needs of your average circus elephant? Well, a new study suggests you might be wasting your time.

Chugging eight glasses of water per day, as many health professionals and nutritionists recommend, is said to do many wonderful things for your health — from preventing urinary tract infections to improving skin tone, promoting weight loss, regulating your digestion, and increasing concentration.

But a new study published in the British Medical Journal suggests that not only does drinking eight glasses of water fail to deliver on those health benefits, but it can actually have detrimental effects — such as hyponatremia, a low-blood-sodium condition common to marathon runners. Margaret McCartney, the Scottish doctor who undertook the study, says those claims of health benefits are "thoroughly debunked nonsense," and come from bottled water manufacturers themselves. (For example Hydration for Health, a research group backed by Volvic and Evian.)

"If you're drinking excessively, if you're drinking beyond thirst, if you're drinking beyond comfort, your kidneys are actually having to work very, very hard," McCartney said.

There are dissenters to McCartney's paper, including a nutritionist from King's College London who countered that McCartney "focused on the more wacky claims made for water," and expressed concern that the results of her study would veer people towards caffeinated and sugary drinks instead.

So how much water should you drink? The Mayo Clinic recommends you drink enough fluids so that "you never feel thirsty," and produce about six cups of "colorless or slightly yellow urine per day." Get those Pyrex measuring cups out, people!