The heat is on, so you've probably got your water bottle out. And that's a good thing. "Every single cell in your body needs fluid to function properly," says Angie Eakin, MD, a family medicine physician at Barnard Medical Center in Washington, D.C. "That's why even mild dehydration can make you irritable, foggy-headed, and headachy." But while it's smart to keep sipping, especially when it's hot and humid, a lot of conventional wisdom about hydrating is just plain false. Read on for the eye-opening scoop.
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Myth: We're all chronically dehydrated
Fact: Not if you eat a healthy diet
Once upon a time, we used to have some water just to wash down a meal. But these days, we're encouraged to drink all day long, on the premise that we've secretly been walking around like parched zombies. Not so, says Barbara Rolls, PhD, a nutrition professor at Pennsylvania State University. The truth is, moisture in food contributes about 20 percent of the fluid you need. So if you avoid "dry" foods like heavily processed crackers, fill up on fruits and veggies and drink when you're thirsty, you should stay well hydrated, even if you're not chugalugging, explains Rolls.
Bottom line: Eating a diet packed with produce helps prevent dehydration throughout the day. Some super-hydrating choices: cucumbers (97 percent water), cauliflower (92 percent water), spinach (91 percent water) and strawberries (91 percent water).
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Myth: It's easy to mistake thirst for hunger
Fact: Your body knows the difference
The thinking here is that you're apt to dive into a big bag of M&M's when what you really need it to swig H2O. Reality check: Snack attacks are usually due to any number of reasons (boredom, habit, stress) besides thirst. In fact, "studies in animals show that being thirsty may actually make you eat less during the day," says Rolls.
You're unlikely to mix up true thirst and hunger because the sensations aren't even similar. "They feel different and are regulated by separate mechanisms in your body," says Rolls. When you're low on fluids, your cell and blood volumes decrease, and you get an unpleasantly dry, tacky-feeling mouth. Hunger, on the other hand, is driven by gut hormones, nutrients and glucose, and it's heralded by stomach rumbles and a sensation of emptiness.
Bottom line: Look out for the thirst and hunger cues above, and drink or eat up as needed. (And if what you're really feeling is boredom or stress, take a stretch break or watch some kitten videos instead.)
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Myth: You need to drink 64 ounces of water a day—at least
Fact: That's a random number
"There's not a lot of hard-core evidence that you have to drink this amount," says Dr. Eakin. The Institute of Medicine says that healthy women should actually consume 91 ounces of H2O a day—but that includes intake from all beverages and food, not just what goes into your water glass. Still, that's only an estimate. You might need more if you live in a hot and humid climate, exercise a ton or are pregnant. Most healthy adults will hit the right amount by following their own thirst cues.
Fact: You could use a drink, but it's not a crisis
Folks who tout this myth would have you believe that thirst is something you should never feel, ever. But thirst is simply your body's way of saying, "Hey, lady, maybe you ought to take a swig from your water bottle." Notes Dr. Eakin, "Our ancestors had to look for fluid; they couldn't just walk to the watercooler." Translation: It's OK to feel a little thirsty—just don't wait too long to grab a drink. Actual dehydration (the kind that endangers your health) comes with more serious ill effects, like migraines and dizziness.
Bottom line: Assuming you're otherwise healthy, thirst is totally normal and not a sign of a major problem. Don't let it reach the point where you feel foggy or get a headache; if you do, start sipping right away. Mild dehydration can be treated by drinking more, but if you have symptoms of severe dehydration, like confusion, extreme thirst or no urination, head to the ER, where you can get intravenous fluids.
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Myth: You should drink a lot during exercise
Fact: Let thirst be your guide
You may think it's good to glug loads of water during spin class—or that it can't hurt. But there is such a thing as overhydration. Hyponatremia, in which the level of sodium in your blood gets too low, can be caused by drinking large volumes of fluid, even with electrolytes. It's rare, but it can be deadly. "There is no reason to drink more than your body needs, and the sensor that tells us how much we need is thirst," says Mitchell Rosner, MD, professor of medicine at the University of Virginia Health System, who authored guidelines on H2O and exercise in the Clinical Journal of Sports Medicine in 2015. You don't have to gulp a gallon of water during a workout if you're not thirsty. Don't trust your "thirst-inct"? Weigh yourself before and after exercising, then drink 16 ounces for every pound lost.
Bottom line: Thirst has worked for thousands of years. Listen to it!
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Myth: Drinking water will curb your appetite
Fact: Maybe, but not for the reason you think.
Though eating soup or another water-rich food at the start of a meal will fill you up and help you consume fever calories overall, "plain water empties out of your stomach quickly," says Rolls. However, she points out, research shows that if you believe water can tame your appetite, it might. Talk about thinking yourself thin.