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January 10, 2020

Do you really need 8 glasses of water a day? Here's what experts say.

Daily Briefing
    Editor's note: This popular story from the Daily Briefing's archives was republished on Jul 14, 2022.

    While many people have made New Year's resolutions to drink more water, research suggests the recent emphasis on water as a "cure all" is overblown, Catherine LeClair writes for the New York Times.

    Cheat sheets: Evidence-based medicine 101

    America's obsession with water

    Water, as "boring" as it may be, has become people's favorite beverage, LeClair writes. In 2016, bottled water sales by volume even surpassed soft drinks as the top beverage in the United States, according to the Beverage Marketing Corp.

    One popular recommendation is that people consume eight glasses of water per day. To get in those eight glasses—or perhaps more—some carry water bottles wherever they go, while others purchase water bottles to leave in the spaces they frequent, like the office or the gym, so they never have to go without, LeClair writes. And some keep track of their hydration using mobile apps or journals to ensure they meet a recommended number of glasses of water per day.

    Our health-focused obsession with water could be due to the fact that it's "marketed as a cure for nearly all of life's woes," LeClair writes.  She explains, "Water is a go-to remedy for a variety of ailments: exhaustion, headaches, digestive problems, inflammation, dry skin, acne."

    The truth about water

    But while some look to water as a fix for pretty much every ailment in the book, research shows that water isn't the cure-all it's cracked up to be.

    Mitchell Rosner, a kidney specialist at the University of Virginia, said, "There's no evidence that a little bit of dehydration really impacts anybody's performance."

    Rosner explained that a lot of hydration studies are performed on athletes, meaning some of the recommendations we read are for people who are at higher risk for dehydration than the average person.

    CDC notes that "there is no recommendation for how much plain water adults and youth should drink daily."

    In fact, Rosner warned that blindly following consumption recommendations, such as the popular eight glasses per day rule, could lead to overhydrating.

    Usually we just "pee … out" the water our body doesn't need, Rosner explained, but in the most severe cases, overhydrating can cause sodium and electrolyte levels to drop to dangerous levels, leading to hospitalization or death. "For those of us who spend all day at a desk, it's best to drink only when we feel thirsty," Rosner said.

    In addition, Joshua Zeigler, a dermatologist at Mount Sinai, said, "It's a complete myth that eight glasses of water are necessary to maintain hydrated skin."

    How did water become so popular—and are there better hydrators?

    According to Michael Bellas, chair of the Beverage Marketing Corporation, "It's no accident" that water is "No. 1."

    Before the 1970s, bottled water was sold mainly as a replacement for tap water. But soon, brands such as Evian and Perrier started advertising bottled water as a "high-end refreshment beverage."

    And once disposable water bottles came under scrutiny for their effect on the environment, colorful reusable water bottles sold by companies such as Nalgene became all the rage. 

    "It was cool to carry a water bottle around," Bellas said. "And it was healthy. It made a statement."

    But research suggests it may be more beneficial to load your water bottle with a different beverage, LeClair writes. For instance, she cites a 2015 study on 72 male subjects found that full-fat milk, skim milk, and orange juice kept them more hydrated than water did. Coffee can also be hydrating, according to Lauren Antonucci, a nutritionist (LeClair, New York Times, 1/4; Reuters/Fortune, 3/10/17).

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