If you've spent any time on social media or been to a sporting event lately, you've probably been bombarded with messages encouraging you to drink more water.
Influential celebrities carry almost 4-liter water bottles with them as the new fashion accessory. Twitter bots are constantly reminding us to spend more time hydrating. Some reusable water bottles even come with motivational phrases to encourage us to drink more water throughout the day.
The purported benefits of excessive water consumption are seemingly endless, from improved memory and mental health to increased energy and improved complexion. "Stay hydrated" became a new version of the old "take care" greeting.
But what exactly does "stay hydrated" mean? "When laymen talk about dehydration, they mean the loss of any fluid," says Dr. Joel Topf, a nephrologist and assistant clinical professor of medicine at Oakland University in Michigan.
But that interpretation "has been completely blown out of proportion," said Kelly Anne Hyndman, a kidney function researcher at the University of Alabama at Birmingham.
Staying hydrated is definitely important, she said, but the idea that simply drinking more water will make people healthier isn't true. It is also not correct that most people are chronically dehydrated, nor that we should drink water all day.
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 drink glass after glass of water throughout the day to maintain it.
Eight glasses a day?
We've all been taught that eight glasses of water a day is the magic number for everyone, but that notion is a myth, says Tamara Hew-Butler, an exercise and sports scientist at Wayne State University in Detroit.
Unique factors, such as body size, outside temperature, and intensity of breathing and sweating, determine how much is needed, she explains. A 200-pound person who has just walked 10 miles in the heat will obviously need to drink more water than a 200-pound office manager who has spent the day in a temperature-controlled building.
The amount of water needed in a day will also depend on health. A person with a condition such as heart failure or kidney stones may need a different amount than someone taking diuretic medications, for example. Or he may have to modify his intake if he was sick, with vomiting or diarrhea.
For most young and healthy people, the best way to stay hydrated is simply to drink when thirsty, says Topf. (Older people in their 70s and 80s may need to pay more attention to getting enough fluids, because feelings of thirst can decrease with age.)
And, despite popular belief, don't rely on urine color to accurately indicate your hydration status, Hew-Butler said. Yes, it's possible that dark yellow or amber urine could mean you're dehydrated, but there's no strong evidence to suggest that the color alone should prompt drinking.
Do I have to drink water to stay hydrated?
Not necessarily. From a purely nutritional standpoint, water is a better choice than less healthy alternatives like sugary drinks or fruit juices. But when it comes to hydration, any beverage can add water to your system, Hew-Butler said.
A popular notion is that drinking caffeinated or alcoholic beverages dehydrates you, but if that's true, the impact is negligible, Topf said. A 2016 randomized controlled study of 72 men, for example, concluded that the hydrating impacts of water, beer, 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, contribute to water intake. Additionally, the chemical process of metabolizing food produces water as a byproduct, which also contributes to intake, according to Topf.
Should I worry about electrolytes?
Some sports drink ads might make you think you need to constantly replenish electrolytes to keep your levels in check, but there's no scientific reason for most healthy people to drink beverages with added electrolytes, Hew-Butler said.
Electrolytes, such as sodium, potassium, chlorine, and magnesium, are electrically charged minerals that are present in body fluids and are important in balancing the body's water. They are also essential for the proper functioning of the nerves, muscles, brain, and heart.
When one becomes dehydrated, the concentration of electrolytes in the blood rises and the body signals it to release the hormone vasopressin, which ultimately reduces the amount of water that is released into the urine so that it can be reabsorbed back into the body. body and regain balance, Hyndman explained.
Unless you find yourself in an unusual circumstance—exercising very hard in the heat or losing a lot of fluids through vomiting or diarrhea—you don't need to replenish your electrolytes with sports drinks or other electrolyte-laden products. Most people get enough electrolytes from food, says Hew-Butler.
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 rarer autosomal dominant polycystic kidney disease, may benefit from making an effort to drink a little more water than their thirst would indicate, Topf said.
But in reality, most healthy people who blame dehydration for their discomfort may feel sick because they're drinking too much water, Hyndman speculated. "Maybe they get a headache or they feel bad, they think, 'I'm dehydrated, I need to drink more,' and they keep drinking more and more and more water, and they keep feeling worse and worse."
If you drink at a higher rate than your kidneys can excrete, the electrolytes in your blood can become too diluted and, in the mildest case, could make you feel "off."
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 sodium levels in the blood drop too low, it can cause brain swelling and neurological problems such as seizures, coma, or even death.
In 2007, a 28-year-old woman died of hyponatremia after drinking more than 7 liters of water over three hours while participating in a radio station's "Hold Your Pee for a Wii" contest, which challenged participants to drink water and then go as long as possible without urinating.
In 2014, a 17-year-old high school football player in Georgia died from the condition after reportedly drinking nearly 1 gallon of water and a similar amount of sports drink.
The condition has become so common among exercisers that when someone collapses during a run, first responders are trained to consider hyponatremia, Topf said, even though developing severe hyponatremia is rare for most healthy people.
How can I know if I am sufficiently hydrated?
Your body will tell you. The notion that staying hydrated requires complex calculations and instant adjustments to avoid dire health consequences is simply nonsense, experts said. And one of the best things you can do is stop thinking about it.
Instead, the best advice for staying hydrated, according to Topf, is also the simplest: drink when you're thirsty. It's that easy.
Christie Aschwanden © The New York Times
Translation: Patricia Sar
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