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Canada Cup National team member Rapha‘l Gagne, hydrates before the start of competition during the Canada Cup XC Race at Bear Mountain Resort in Victoria, B.C., on March 5, 2016.

CHAD HIPOLITO/The Globe and Mail

Have you encountered the #HydrationChallenge? It’s a social-media campaign that encourages you to drink 2.5 litres of water a day and post about it, and thousands of people are participating. There’s just one problem: It’s based on a myth.

“This idea emerged decades ago as a misinterpretation of some guidelines from the federal government of the U.S.,” said Tim Caulfield, Canada Research Chair in Health Law and Policy. The 1945 document said that, “a suitable allowance of water for adults is 2.5 litres daily,” but there was another part to that: “Most of this quantity is in prepared foods.”

“Most of the foods we eat contain some water. Soup has more than steak, but there’s still some water there,” said Gerry Kasten, a lecturer in dietetics at the University of British Columbia. Moreover, the idea that only pure H2O will hydrate us is not accurate. Though caffeine and alcohol do have a diuretic effect, “caffeinated beverages and alcoholic beverages can be calculated in the amounts we drink,” he said. “They stimulate urination but they do contribute to overall hydration. There’s lots of evidence for that.”

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That’s not to say that water isn’t important – most of the body’s chemical reactions take place in an aqueous environment, and it’s better to drink water than sugary pop or alcohol – but, Mr. Kasten said, “We’d be a sorry species if we hadn’t evolved to ensure that we were able to make use of available water in times of scarcity.”

In truth, the rules around drinking water are extremely straightforward: If you’re thirsty, drink. If your pee is a pale yellow colour, you’re not dehydrated. Some people need more water than others, and their thirst will guide them to the right amount. If you’re in a hot place or have exercised, you’ll probably feel thirstier and therefore naturally will want to drink more water. An alkaline or cucumber-infused water won’t hydrate you more than tap, and drinking tons of water before or after your COVID-19 vaccine won’t change your side effects.

But surely drinking water above our thirst levels will hydrate us better and therefore perhaps lead to younger-looking skin or an indefinable glow? Not so. “The idea that you drink water, it diffuses to the outer layer of skin and you get radiant is simplified and not true to biology,” said Dr. Aegean Chan, a dermatologist in Santa Barbara, Calif. “There is no evidence that drinking water will give you better quality of skin or reduced dark circles.”

There’s no buildup of toxins that needs to be flushed out, either. “That is magical thinking,” Dr. Chan says. “The skin doesn’t play a role in eliminating metabolic by-products. This is all pseudo-science.”

All that said, is it really such a problem if people want to get involved in a challenge to up their intake of water? One of Mr. Kasten’s biggest issues with hydration challenges, apart from the lack of science, is the privilege bound up in them. “There are people in Canada who cannot access clean water because of lack of privilege,” he says. “Access to a washroom is a privilege.” He’s also concerned that, like many wellness trends, from superfoods to jade eggs, it’s actually about trying to sell you something, whether it be bottled water or water bottles.

Mr. Caulfield shares these concerns. “Some of this is marketing from the bottled water industry, which is massive,” he said. “The more amorphous harm is this acceptance of something that’s science-free that invites people to believe in magical thinking, which we’ve seen in the pandemic is not a good theme.”

For women, drinking water is sold as a pathway to being slimmer and more attractive, unlike for men, where it’s often about athletic performance. “Both go to an idea of virtue – if you’re not doing this, you’re not fulfilling your obligations to your self and society,” Mr. Caulfield said. “Drinking more water gives you a sense that you’re trying to build a better life. It becomes part of your personal brand.”

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Mr. Kasten points out that some of the fallacies around water consumption are also connected to troubling societal pressures – for example, that our bodies can’t tell the difference between hunger and thirst and therefore if we’re hungry, we should sip water before snacking. In reality, we all know that hunger and thirst actually feel quite different. “This discourse is propagated by diet culture: ‘Don’t trust your body!’” he said.

He believes hydration challenges may ultimately be harmful to the very thing we’re trying to improve – our health. “We are taught, often from a very young age, that we should be attentive to an external source to regulate our eating, not to our internal cues: ‘Finish your plate.’ ‘A portion of vegetables is 1/2 cup,’ and so on,” he said, pointing out the breastfed babies are allowed to control how much they consume at any feeding, but after that, we start to learn that we should follow external cues to achieve the “correct” diet. “‘Hungry really means thirsty’ is just another misguided directive to teach people that they should not trust their bodies,” he says.

Dr. Chan says that having a daily target for an everyday activity can be stressful. “It’s really insidious to put the responsibility for health and well-being onto individuals, as though you are solely responsible for your body functioning correctly,” she said. “My organs are much more reliable than I am. A healthy kidney or liver won’t just forget to function one day.” Ultimately, it’s worth thinking about how helpful it is to place artificial goals on the things we do. “There’s been some research around step-counting that when you quantify everything, it just makes life less fun,” Mr. Caulfield said. The experts are united: When it comes to drinking water, get rid of the challenge, and go with the flow.

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