Do you need 8 glasses of water per day? 6 myths and truths about drinking water

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Certainly, staying hydrated does contribute to overall health, according to experts like Dr. Angie Eakin, a family medicine physician at Barnard Medical Center in Washington, D.C. 
"Every single cell in your body needs fluid to function properly," she told Health.com. "That's why even mild dehydration can make you irritable, foggy-headed, and headachy."
But numerous misconceptions have flowed from the basic principle that staying hydrating is a good thing.

Here are six of the most prominent myths about drinking water, followed by the icy cold truths:

6 myths about drinking water, debunked

Myth: Drinking lots of water will curb your appetite.
Fact: The only weight-loss benefit of drinking lots of water is that it keeps your mouth too busy to eat.

As part of coverage on the "Top 10 Fitness Myths," Fitness magazine experts crushed the dieting myth that drinking lots of water makes you less hungry. "Sorry to tell you this," the Fitness editors wrote. "You may eat less, because you're too busy trucking back and forth between the bathroom and dinner table, but that's about it."

Myth: You might be thirsty when you think you're hungry.
Fact: You're probably hungry when you think you're hungry.

While boredom, habit or stress might make you eat when you're not hungry, your body is unlikely to mix up hunger and thirst, Penn State nutrition professor Barbara Rolls, Ph.D., told Health.com. The sensations aren't even similar. "They feel different and are regulated by separate mechanisms in your body," Rolls said. When you need hydration, cell and blood volumes tank, giving you an unpleasantly dry, tacky-feeling mouth. There's little chance you'll mistake that for the sensation of hunger, which takes cues from gut hormones, nutrients and glucose and is signaled with a rumbling stomach and a sensation of emptiness.

Myth: You need to chugalug water constantly or risk imminent dehydration.
Fact: A healthy diet and drinking when you're thirsty will hydrate you just fine.

There's no need to constantly gulp down water, according to Rolls. As she told Health.com, the moisture in food alone provides about 20 percent of the fluid you need. Instead of randomly chugging water throughout the day, Rolls recommended avoiding dry foods like heavily processed crackers and filling up on hydrating produce like cucumbers, which are 97 percent water. Do that and drink water when you're thirsty, and your hydration levels should be fine, Rolls said.

Myth: You can overhydrate easily.
Fact: It's unusual to drink too much water.

People commonly worry about the risk of drinking too much water, but that's low on the list of concerns, said Nicole G. Morgan, a registered dietitian and nutritionist who practices in Atlanta.
She said overhydrating is much more difficult than most people think. "You would have to consume your full water requirement for the day in a short time frame for it to become dangerous." To avoid even this slight danger of drinking too much water, Morgan recommended spreading out an increase in water intake over the course of a day. "That approach to hydration is generally regarded as safe and healthy," she said.

Myth: Bottled water fortified with electrolytes is healthier.
Fact: Most Americans don't need fortified drinks.

In a 2015   evaluation of coconut water and other sports drinks, Consumer Reports concluded that most Americans don't need fortified bottled water. The consumer watchdog noted that the labels on the drinks said they contained added electrolytes, minerals that help regulate muscle function and water balance, which can be lost during long intense workouts. CR then concluded that few people in America exercise so vigorously as to need to replenish electrolytes. 
CR also quoted Leslie Bonci, a dietitian and director of sports nutrition at the University of Pittsburgh Medical Center, who said, "Any liquid is going to be hydrating, even coffee. Do vitamins and minerals add to hydration? No. What's hydrating is the fluid."

Myth: Everyone needs eight 8-ounce glasses of water a day.
Fact: There's no basic rule about how much water you need to stay hydrated.

This is one of the most widespread myths about drinking water, but on closer examination it really doesn't hold up, according to diet and nutrition experts at Consumer Reports on Health in a recent report on "How to Stay Hydrated." They noted that an appropriate amount of water per day can vary "a good bit" from person to person. In general, people who are heavier or taller or more active need to take in more water to cover their losses. In addition, hot or humid weather might increase a person's need for water intake.
 To make sure you get enough water, CR experts recommended taking these steps:

Even caffeinated drinks count towards hydration, Janet Mentes, Ph.D., a professor at the UCLA School of Nursing, told CR. While coffee and tea and some sodas are mild diuretics that can cause you to urinate more often, they add more to your liquid stores than you'll lose from extra urination, she said.