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Recent American culture seems to obsess over hydration. I personally remember the turning point being during my high school years, around 2000, when carrying bottled water became more common than excusing oneself for a drink or hitting the water fountain between classes. Media reports and ads only fuel the fire, and most water and sports drink companies claim that we’re either constantly dehydrated (and therefore desperately need their product) or that further hydration will make us feel better, improve our athletic performance, and give us radiant skin.
But the hydration obsession, or more accurately the public fear of dehydration, has little scientific basis and is mostly founded on a few well-worn anecdotal statements. One of the more familiar is that it’s “healthy” to drink “a minimum of 8 glasses of water per day.” This one assumes that most people are already chronically dehydrated, and lots of other outlandish statements about the country’s lack of water intake surround it. Some of these rumors include that 75% of Americans are constantly dehydrated, that most people mistake deep thirst for hunger and therefore eat instead of drink, and that dehydration is the #1 cause of daytime sleepiness.
 The most interesting part of the 8-glasses rule is that even nutritionists and researchers don’t know how or where it originated. In 1945 a US National Research Council board recommended ingesting 2.5 liters of water per day, but they qualify that most of this intake could be satisfied by water content in food. And contrary to another rumor about the dehydrating effects of coffee, tea, and juice, drinking these also counts toward a person’s daily fluid intake. (For a fascinating scientific discussion of the 8x8 myth and the 1945 recommendations, check out this article from the Dartmouth Undergraduate Journal of Science.)
Many of the wild stats to justify the 8-glasses argument are similar to those posed by Fereydoon Batmanghelidj, an Iranian-born physician who believed that water-drinking, in lieu of medication, cures most illnesses. He self-published his findings in a polarizing book; fans of his work claim that drinking more water has cured ailments from allergies and headaches to ulcers and led to rapid weight loss, while many in the scientific community believe him to be a quack, noting that he was licensed as a naturopath in the United States but never a physician.
The pesky truth underlying these claims is that every individual has a different threshold for water intake, and that the body has an extremely accurate barometer to guide our fluid intake: thirst. But another widely held belief says that thirst is in fact inaccurate, and that a sensation of thirst means the body is already dehydrated. As a hydration-obsessed runner myself, I wish I had a nickel for every time I’ve heard or read “Hydrate before you’re thirsty” in running-related media. But most nutritionists agree that the secret to staying properly hydrated is to trust your thirst: listen to your body and drink when you’re thirsty. It’s also important to remember that eating salty foods can cause thirst, even if dehydration isn’t occurring. Urine color is also a good indicator of adequate hydration when thirst is not.
Both downplaying and obsessing over hydration can be dangerous. Individuals working strenuously or adjusting to a much hotter climate can easily become dehydrated and succumb to heat stroke or even death. But drinking more fluid than the kidneys can handle causes hyponatremia, which can also be deadly. That term is often associated with rare freak accidents like deaths in water-drinking contests, but less severe cases of exercise-associated hyponatremia (EAH) are much more common in endurance athletes. A 2015 study found that 13% of 2002 Boston Marathon runners experience EAH, although most cases were mild. In light of EAH concerns, there’s a growing contingent of researchers who are now recommending that even athletes drink only when thirsty.
Obviously each individual knows their body best, and if extreme fatigue, dizziness, or other scary symptoms follow thirst, dehydration is probably a real concern. But anecdotal rules and recommendations do little but provoke anxiety, and it’d probably be best for the country—myself included—to obsess a little less about hydration.
Image credit: Beatrice Murch / CC BY 2.0
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