You Might Not Need as Much Water as You Think

Eight glasses of water per day may be too much for some people

Water, water, everywhere — but how much should you drink?

Staying hydrated is a bit of a Goldilocks tale: not too much, not too little, but just right. And the widely circulated recommendation for eight 8-ounce glasses a day has no scientific backing, according to Aaron E. Carroll, MD, writing in The New York Times.

Dr. Carroll, a professor of pediatrics at Indiana University School of Medicine, coauthored a 2007 article on medical myths that debunked the eight-glass recommendation. Despite that article, he said he still sees the recommendation frequently.

A 2010 Dutch study published in Nederlands Tijdschrift Geneeskunde noted that healthy people excrete about 500 cubic centimeters (CCs) of water a day on average. That’s a little more than 2 cups.

The authors of this study said a total daily fluid intake of 3,000 CCs for men and 2,500 for women is more than adequate. Those figures include fluids from all sources, however — not just water. For most people, those amounts allow for normal body functions, sweat loss, respiration and urination.

In addition to water, potential sources of fluid include coffee, tea, soft drinks, fruits, vegetables and alcoholic beverages.

Too much water can be a problem, according to a 2015 study in the Clinical Journal of Sports Medicine. A panel of medical experts who analyzed the risk of drinking too much water during athletic activity noted that aggressively drinking water can be dangerous. Too much water can cause the level of sodium in the body to drop too low, which can be deadly.

The authors of this study recommended paying attention to thirst and drinking only when thirsty.

“There is no formal recommendation for a daily amount of water people need,” Dr. Carroll wrote in his article for the Times. “That amount obviously differs by what people eat, where they live, how big they are and what they are doing. But as people in this country live longer than ever before, and have arguably freer access to beverages than at almost any time in human history, it’s just not true that we’re all dehydrated.”