How much water should I drink? 5 myths about hydration answered

Brierley Wright, M.S., R.D.
June 30, 2011


Jupiterimages/© Getty Images
Jupiterimages/© Getty Images

Jupiterimages/© Getty Images

How many glasses of water should I really be drinking every day? And does my coffee habit cancel out my water-drinking efforts?

These are the questions I wanted the answers for when I edited the hydration story written by award-winning writer Rachael Moeller Gorman in the August 2011 issue of EatingWell Magazine. I got my questions answered and some really surprised me, which is what inspired this post. So here you go: 5 common myths about water and hydration busted!

Myth or Truth: I need 8 glasses of water a day.
Myth. The Institute of Medicine says adult men actually need about 13 cups (3 liters) per day of fluid; adult women need about 9 cups (2.2 liters) of fluid. (You get about an additional 2 1/2 cups of fluid from foods.)

“But one size doesn’t fit all,” says Leslie Bonci, R.D., C.S.S.D., director of sports nutrition at the Center for Sports Medicine at the University of Pittsburgh Medical Center and dietitian for the Pittsburgh Steelers. Your size and activity level affect your fluid requirements. Simply put, the larger and more active you are, the more you’ll need.

“The easiest thing that anybody could do on a daily basis is monitor their urine color,” says Douglas Casa, Ph.D., A.T.C., who studies hydration at the University of Connecticut. “Lighter urine color—like lemonade—means you’re generally well-hydrated. If it’s darker, like apple juice, you are most likely dehydrated.”

Older adults’ fluid needs don’t change, but they’re more likely to become dehydrated because their sense of thirst declines. Pregnant women and nursing mothers need slightly more water. Some medications, such as antihistamines and certain antidepressants, increase your fluid needs too.

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Myth or Truth: Coffee and tea dehydrate you.
Myth. While caffeine is technically a diuretic (it increases water excretion from our bodies), you retain most of the water from caffeinated beverages, such as coffee, tea and soft drinks. Alcohol, on the other hand, particularly at high doses, can cause you to excrete more than you consume. One drink, especially of beer, won’t do much (it’s about 92 percent water), but wine and hard liquor have more of a dehydrating effect because of their higher alcohol content.

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Myth or Truth: The more water, the better.
Myth. It is possible to overdo it. Water intoxication, or hyponatremia, a serious condition when blood sodium levels drop precipitously, can be caused by sweating excessively over several hours and drinking way too much water (versus a sports drink) while not eating or urinating (which often slows during intense physical activity). This could happen to someone who engages in a long athletic event (e.g., a marathon or multi-day hike). Symptoms include confusion, disorientation, weakness and nausea. Hyponatremia can lead to seizures, coma and death without prompt medical attention.

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Myth or Truth: Drinking water can help me slim down.
Truth. “If someone chooses water in place of calorie-containing beverages, overall calorie intake is less and they may lose weight,” says Bonci. A 2010 study in the journal Obesity found that adults who drank two cups of water before a meal ate less at the meal and lost more weight over 12 weeks than the group who didn’t drink water before eating.

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Myth or Truth: Staying hydrated prevents wrinkles.
Myth. When a person is severely dehydrated, skin is less elastic. This is different than dry skin, which is usually the result of soap, hot water and exposure to dry air. And, no, unfortunately, drinking lots of water won’t prevent wrinkles.

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How do you stay hydrated?

Brierley's interest in nutrition and food come together in her position as nutrition editor at EatingWell. Brierley holds a master's degree in Nutrition Communication from the Friedman School of Nutrition Science and Policy at Tufts University. A Registered Dietitian, she completed her undergraduate degree at the University of Vermont.

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