For the past 50 years, nutritionists and other health experts have been exhorting Americans to drink more water. And if the ubiquity of the water bottle is anything to go by, this message has been heard loud and clear. Everywhere you look—college campuses, commuter trains, yoga classes—you see the plastic water bottle in all its variations.
But now that it's been firmly established in your psyche, and you either dutifully swig water constantly or feel guilty for not doing so, new research lets you off the hook. As it turns out, much of the water craze springs from a deep well of misinformation. Our experts debunk some of the most popular water myths and relieve your guilty conscience in the process.
Myth: You need eight 8-ounce glasses of water a day to be healthy.
The problem, as Valtin explains in an American Journal of Physiology study in 2002, is that most of that allotment already comes from the foods we eat. He not only pooh-poohs the need for most people to consume eight 8-ounce glasses of water every day but also writes that the recommendation is potentially harmful "in making people feel guilty for not drinking enough."
The crux of the miscalculation hinges on the definition of water. "The consumer ended up thinking only plain water counts," says Ann Grandjean, Ph.D., a hydration researcher and the executive director of the nonprofit Center for Human Nutrition in Omaha, Nebraska. But almost all liquids—including tea, coffee, and beer—count toward the daily water intake, she says.
So, how much should you be drinking? If you would like hard and fast guidelines, you can follow the advice of the National Academies' Institute of Medicine, which reconfigured its recommendations for water intake last February. After reviewing more than 400 studies, including Valtin's, the authors set the general daily intake for women at roughly 91 ounces and for men at approximately 125 ounces.
But remember, these numbers include both food and water. The average American gets 20 percent of his or her water intake from food. Even spaghetti is 66 percent water (see the chart at the end of this article). The remaining 80 percent comes from all beverages. Taking that into account, by the institute's reckoning a woman should drink 72.8 ounces (nine 8-ounce glasses) daily and a man 100 ounces (12.5 glasses). But, unlike what you may have heard before, those 72.8 ounces can come from coffee, tea, or soda—not just water.
Myth: Caffeinated beverages zap your body's water reserves.
In 2000, she published a study on caffeine consumption and hydration in the Journal of the American College of Nutrition. For the study, Grandjean and her colleagues recruited 18 healthy men and on various days had them drink 59 fluid ounces of liquid that included varying amounts of plain water, diet cola, and coffee, depending on subjects' body mass. Researchers tested each participant's body weight, urine, and blood before and after drinking. The authors discovered the body doesn't discriminate between regular and decaf beverages when it comes to hydration. After the study exonerated caffeine, Grandjean, like Valtin, was stunned by the public's reaction. "Consumers started calling and saying 'This is wonderful,' " she recalls with a chuckle. "All those closet caffeine addicts—it was as if they'd all been liberated."
Myth: If you're thirsty, you're already dehydrated.
That said, the fact that you're not dehydrated yet is no reason to avoid water. "Thirst is the first indicator of the body's need for water," says Dee Sandquist, spokesperson for the American Dietetic Association. And people who shrug off their thirst will find themselves on the path to dehydration. Signs to look for include headache, dry mouth, rapid pulse, and light-headedness.
Myth: Urine should be clear.
Myth: Drinking lots of water suppresses the appetite.
Myth: Bottled water is always better than tap water.
To determine the health of your municipality's water supply, visit the Environmental Protection Agency's drinking water site (epa.gov/safewater/dwinfo). To find out if lead from old pipes is seeping into your taps, consider a home water test, such as Watersafe (watersafe testkits.com). If any contaminants show up, try using a filter appropriate for the type of contaminant, suggests Jeff Migdow, M.D., a holistic physician affiliated with Kripalu Center for Yoga & Health in Lenox, Massachusetts.
If you'd rather buy bottled, splurge on spring water from a reputable source. "Much of bottled water is simply tap water that's been filtered," says Migdow. Indeed, a 1999 report from the Natural Resources Defense Council cites government and industry findings that roughly 25 percent of bottled water is nothing but plain tap water. If you're curious about the source of your favorite brand of bottled water, go to nsf.org/consumer.
Catherine Guthrie is a health writer and yoga instructor in Bloomington, Indiana.