What You Really Need To Know About Dehydration

You’ve heard it time and again: Water is the elixir of life. And it’s true. Your body relies on water for everything from temperature control to keeping your joints lubricated. But as simple as it seems, there are a lot of hydration-related myths and misconceptions swirling around out there.

“Drink more water,” for example, is often recommended as step No. 1 for myriad health goals, like immune function, beating dry skin, and more. But in fact, while you do need water for literally millions of your body’s daily processes, it’s not as though water is a panacea. For example, unless you’re sick, your body is really good at managing your fluid balance on its own. It will tell you when you’re thirsty and you need more water — all you have to do is listen.

Ahead, we’ll cover what you really need to know about hydration and dehydration, minus all the myths.

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Photographed by Eric Helgas.
The 8x8 rule is basically made up.
First things first: You’ve probably heard a million times that you should be drinking 8 ounces of water 8 times a day to avoid dehydration. But this long-standing myth isn’t based on evidence. It’s mostly stuck around simply because it’s easy to remember.

All that said, if you’re still looking for a goal, the Institute of Medicine set an evidence-based general recommendation of 91 ounces (or 2.7 liters) of fluid per day for women.
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Photographed by: Nolan Rockie.
If you’re hungry, don’t drink water — eat something.
An often-repeated but misguided piece of diet advice is to drink water every time you feel hungry between meals. The logic is that dehydration and thirst are often mistaken for hunger, and so instead of risking snacking-related weight gain, you should just drink some water and hope the hunger goes away. But advice like this is part of a dangerous diet mentality that can create an unhealthy relationship with food, says Christy Harrison, RD. “If you’re drinking water instead of having snacks, that means you’re missing out on [the fuel] your body needs.”

If your body is telling you it needs food, listen to it. “If you’re thinking that you’re hungry, and you’re actually thirsty, and you quote-unquote mistakenly eat something, that’s not going to hurt you,” Harrison says. And if you want, down a glass of water with your snack, too.
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Photographed by Winnie Au.
Thirst doesn’t automatically mean dehydration.
One of the most bogus myths out there is the idea that once you start to feel thirsty, you’re already dehydrated. The truth is that what we know as “thirst” is a complex physiological process that works to prevent dehydration. Your brain actually has a number of very precise mechanisms for monitoring water in your cells, with each of these being sensitive enough to detect when the water in your body decreases (or increases) by a few hundred millileters.

As you sweat and breathe throughout your day, you lose some water and your cells react by shrinking. This shrinkage triggers your brain to tell you to drink up. As long as you listen to that urge, you will have corrected the problem before it becomes one.
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Water is the only thing that could possibly be thought of as a “detoxifier.”
There are plenty of dangerous ideas about how to “detox” or “cleanse your body of toxins" (note: please don’t do a detox diet), but staying hydrated is pretty much the only one that’s even sort of defensible.

That’s because drinking enough water helps ensure your kidneys — one-half of your body’s built-in cleansing system (the other half is your liver) — stay healthy.

While only severe dehydration can actually begin to affect kidney function, even being slightly dehydrated on a regular basis can increase your risk for urinary tract infections and kidney stones, according to a 2010 study in the journal Nutrition Today. Every day, your kidneys filter between 120 and 150 quarts of blood and make about one to two quarts of urine. And they need water to dissolve nutrients and help make sure waste products do not build up in the kidneys, leading to stones.

The good news is, again: Your body is pretty good at alerting you to the potential for dehydration via your trusty thirst mechanism. Keep your water bottle nearby, and your kidneys will thank you.
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Photographed by Amelia Alpaugh.
You can eat your water.
Going back to the idea that water is the elixir of life, H2O is a component of every living thing — and that includes the stuff we eat. The Institute of Medicine says that 20% of your fluid intake should come from food (and yes, that’s included in the 91 ounces).

Options like soup and oatmeal will get you a good helping of fluid, but the most water-rich foods are fruits and vegetables. Good old watermelon is more than 90% water, for example, while cucumbers, celery, and certain lettuces are roughly 95% water.
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Photographed by Rockie Nolan.
Coffee probably isn’t going to dehydrate you.
Neither is tea or any other caffeinated beverage. While it’s true that caffeine can act as a mild diuretic, meaning it can make you have to pee more often, this effect is not strong enough to create a net loss of fluid. In other words, say you drink a large coffee: The amount of water in that beverage is enough to offset anything you might lose by urinating afterward.

Plus, other research suggests that regular coffee drinkers can adjust to the habit. So, over time, caffeine becomes even less of a diuretic. Even more reason to enjoy your regular Starbucks runs: they're energizing and hydrating.
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Photographed by Rockie Nolan.
You don’t need to chug water during your workout, either.
It’s true that if you’re a regular at your gym (especially if you tend to finish your workout dripping in sweat), you need to focus even more on hydration because you’re losing fluid often. However, this doesn’t mean you need to build in a strict hydration routine before, during, and after. Instead, hydration should be a priority all day long.

This way, you will walk into the gym in optimum fluid balance, which not only helps prevent a major water deficit later — it also ensures you’ll get your best workout, since even slight dehydration can cause an energy lag. Then, while you do your thing, just have your water bottle nearby in case you feel thirsty.

The caveat to all this: If you are working out for long periods (an hour or more) or it’s especially hot and humid in your gym or outside, it’s a good idea to replace electrolytes as well. You can do this by simply grabbing a sports drink or coconut water afterward.
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Photographed by: Winnie Au
Dehydration is not the cause of your skin woes.
Is your skin looking drab? Are you worried about wrinkles? Sorry, but drinking extra water is not the skin miracle the internet would like you to believe.

While there is some truth to this myth, in that your skin is made of cells and all of your body’s cells need adequate water to function at their best, taking in more fluid than you need is mostly just going to make you have to pee more.

There have been multiple studies to test the persistent myth that hydration solves all, and back in 2010, the journal Clinical Dermatology published a review of all the available evidence. It has such a delightfully snarky conclusion, it deserves to be quoted in full: “We have found no scientific proof for this recommendation; nor is there proof, we must admit, that drinking less water does absolutely no harm. The only certainty about this issue is that, at the end of the day, we still await scientific evidence to validate what we know instinctively to be true — namely, that it is all a myth.”
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Photo by: Winnie Au.
Sometimes, though, water’s not enough.
If you are working out for long periods (like an hour or more) or it’s especially hot and humid in your gym or outside, it’s a good idea to grab a sports drink afterward.

That's because when you're sweating a lot, you're not just losing water — you're also losing important electrolytes like sodium and potassium. These minerals are important for a variety of your body's processes, from maintaining your fluid balance to helping your muscles contract. So in other words, you need them as much as you need plain old water.
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Photo by: Lauren Perlstein
Real dehydration can be serious.
Although there are plenty of reasons to not stress over your hydration status, there are times when you should be thinking about it, like when you’re spending a full day at the pool or beach.

In most cases, slight dehydration can be remedied by simply drinking something. If it gets serious enough, however, it can contribute to other problems, such as heat exhaustion — and it can sneak up on you.

For example, if you’re doing something active in the water — pool volleyball, snorkeling, or the like — you might not realize how much you’re sweating. Another common reason for dehydration: day drinking. Unlike coffee and tea, alcohol is a true diuretic, which means you will likely be losing fluid if you’re only drinking margaritas all day.

To stay safe, pack plenty of bottled water in your cooler alongside that margarita mix and drink just plain water between cocktails. Look out for symptoms like dizziness, nausea, or cramps. If you experience any of these, move to a cooler environment (in the shade or inside with AC) and drink plenty of fluids, stat. If you don’t cool down, heat exhaustion can quickly escalate to heat stroke, which can be life-threatening.
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Over-hydration can be serious, too.
As dangerous as dehydration is, it is also possible to overdose on water. You may have heard this referred to as “water intoxication,” but the correct term for it is hyponatremia. It happens when the level of sodium in your blood gets too low. Most commonly, it’s caused by an underlying health issue or a medication that makes you sweat a lot, but it can also happen when you drink too much water in a short period of time, which dilutes the sodium in your blood.

For people without underlying health issues, the risk of hyponatremia is highest during the times you’re sweating and drinking a lot of water, so it’s most often a problem among marathon runners or other athletes.

Although it’s still considered rare, it might be more common than previously thought. A 2005 study of runners participating in the Boston Marathon found that 13% of runners had hyponatremia in provided blood samples at the end of the race, even though they didn’t have any symptoms (nausea is one common sign). Even though 13% is a relatively small number, this is still a big deal, because a rapid drop in sodium levels can lead to swelling in the brain, which can be life-threatening and requires immediate medical attention. Per the Mayo Clinic, reproductive-age women are most at risk for serious brain complications of hyponatremia, possibly because of the way female sex hormones affect sodium balance.

Following the deaths of two high school football players from hyponatremia, the Clinical Journal of Sports Medicine published a report from a group of 17 exercise scientists urging athletes (and coaches) to listen to their bodies rather than following more strict hydration routines. "Our major goal was to re-educate the public on the hazards of drinking beyond thirst during exercise," one of the authors of a report said in a statement.

For regular gym-goers, this isn't a huge concern. But if you're training for a marathon or doing another activity that requires long periods of exercise, the best thing to do is drink only when you're thirsty, rather than worrying about replacing a certain amount of fluid every hour on the hour, as previously recommended. It's also a good idea to choose sports drinks that have electrolytes such as sodium in them, to help keep your levels up.
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