Remember when you were a kid and all your coaches and camp counselors and those vaguely hippie-ish guys who took your youth group hiking would tell you to drink, even when you weren’t thirsty? Turns out they were trying to murder you.

The Clinical Journal of Sport Medicine published new guidelines on hydration that essentially boiled down to “Drink only when you’re thirsty.” That sounds like something that doesn’t need to be said, except everyone who has done even amateur sports, or gone hiking or camping, has been advised to keep drinking all the time, even when they’re not thirsty. I remember hiking instructors who told people to drink until their urine was completely clear. This is one of the pieces of advice that the journal specifically warns against.

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Too much liquid leads to hyponatremia. The overworked kidneys can’t excrete water fast enough. The sodium levels in the body get too low. Sodium helps cells regulate their fluid intake. Too little sodium in the liquid surrounding cells, and osmosis causes liquid to pass through the cell membrane and pour into the cell. The body’s cells swell, and can even burst.

In 2014, two different football players died due to encephalopathy, a disorder of the brain, caused by hyponatremia. Many other athletes became seriously ill. Coaches and other athletics organizers (including the military) worry that dehydration will make their charges sick, or just slow them down, and tend not to worry about the relatively remote chance of fatal hyponatremia. The journal states that, if anything, fears of dehydration are overhyped: “Although somewhat controversial, the bulk of evidence supports that mild levels of dehydration (up to 2%-3% of body weight) are well tolerated and minimally affect athletic performance.” Hyponatremia, on the other hand, has been made to seem more unlikely than it is, given how much current athletics instructors push liquids.

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To be fair, the athletes who died had taken in staggering amounts of water. Within a few hours, one had consumed eight liters and the other sixteen liters of water. Still, the deaths were easily preventable, and dehydration is easily remedied, especially when we have an internal gauge letting us know when we’re dehydrated The journal recommends letting athletes drink only when they’re thirsty, and pushing them to drink more only after intense exercise, or if they are suddenly in extremely hot environments.

Image: Taro Taylor