Do you really need to drink 8 glasses of water a day?
Stop overthinking and ditch the calculations. Drink only when you’re thirsty — it’s that simple
You’re often bombarded with encouragements to drink more water. The purported benefits of excess water consumption are seemingly endless, from improved memory and mental health to increased energy to better complexion. “Stay hydrated” has become a new version of the old salutation “Stay well”.
But what, exactly, does “stay hydrated” mean? “When lay people discuss dehydration, they mean loss of any fluids,” said Dr Joel Topf, a nephrologist and assistant clinical professor of medicine at Oakland University, US.
But that interpretation “has been completely blown out of proportion”, said Kelly Anne Hyndman, a kidney function researcher at the University of Alabama, US.
From a medical standpoint, Topf said, the most important measure of hydration is the balance between electrolytes such as sodium and water in the body. And you don’t need to chug glass after glass of water throughout the day to maintain it.
How much do I really need to drink?
We’ve all been taught that eight glasses of water per day is the magic number, but that notion is a myth, said Tamara Hew-Butler, an exercise and sports scientist at Wayne State University, US.
Unique factors such as body size, outdoor temperature, and how hard you’re breathing and sweating will determine how much water you actually need, she said. A 200-pound person who just hiked 10 miles in the heat will obviously need to drink more water than a 120-pound office manager who spent the day in a temperaturecontrolled building.
The amount of water you need in a day will also depend on your health. For most young, healthy people, the best way to stay hydrated is simply to drink when you’re thirsty, Topf said. Those who are older, in their 70s and 80s, may need to pay more attention to getting sufficient fluids because the thirst sensation can decrease with age.
Do I have to drink water to stay hydrated?
Not necessarily. From a purely nutritional standpoint, water is a better choice than lesshealthy options such as sugary sodas or fruit juices. But when it comes to hydration, any beverage can add water to your system, Hew-Butler said.
One popular notion is that drinking beverages with caffeine or alcohol will dehydrate you, but if that’s true, the impact is negligible, Topf said. A 2016 randomised controlled trial of 72 men, for instance, concluded that the hydrating impacts of water, lager, coffee and tea were nearly identical.
You can also get water from what you eat. Fluid-rich foods and meals such as fruits, vegetables, soups and sauces all contribute to water intake.
But drinking more water, even when I’m not thirsty, will improve my health, right?
No. Of course, people with certain conditions, such as kidney stones or the more rare autosomal dominant polycystic kidney disease, may benefit from making an effort to drink a little more water than their thirst would tell them to, Topf said.
In the most extreme case, drinking too much water in a short period of time could lead to a condition called hyponatremia, or “water intoxication”. “This is very scary and bad,” Hyndman said. If the sodium levels in your blood get too low, it can cause brain swelling and neurological issues such as seizures, coma or even death.
— THE NEW YORK TIMES
