by Catherine Guthrie

Water is good for both body and soul, but you don’t need to drink as much as you might think. Here’s the truth about what’s sufficient, plus five other myths about water.

For the past 50 years, nutritionists and other health experts have been exhorting Americans to drink more water. If the ubiquity of water bottles is anything to go by, the message has been received loud and clear. But now, updated research lets us off the hook. It turns out that much of the water craze springs from a deep well of misinformation. Our experts debunk some of the most popular water myths.

MYTH: You need eight, eight-ounce glasses of water a day to be healthy. TRUTH: The familiar eight-by-eight rule is likely based on misinterpretation, rather than scientific certainty, says Dr. Heinz Valtin, a kidney specialist, textbook author and retired professor at Dartmouth Medical School, in Hanover, New Hampshire. Valtin traces the prescription to a 1945 recommendation by the Food and Nutrition Board of the National Research Council to take in, “1 milliliter for each calorie of food.”

In a study published in the American Journal of Physiology in 2002, Valtin explains that most of that allotment already comes from the foods we eat. He not only discredits the need for most people to consume this “mythical” amount of water every day, but writes that the recommendation is potentially harmful, by making people feel guilty for not drinking enough.

“The consumer ended up thinking only plain water counts,” says Ann Grandjean, Ph.D., a hydration researcher and medical nutritionist with the University of Nebraska Medical Center, in Omaha. But almost all liquids—including tea, coffee and beer—count toward the daily water intake, she says.

So, how much should you be drinking? Researchers at the National Academy of Sciences’ Institute of Medicine, after reviewing more than 400 studies, including Valtin’s, set the general daily intake for women and men at about 91 and 125 ounces, respectively. The average American receives 20 percent of this daily water intake from food. The remaining 80 percent comes from all beverages—not just water.

MYTH: Caffeinated beverages zap the body’s water reserves. TRUTH: Grandjean first became interested in the reputed link between dehydration and caffeine while working as a consultant to the United States Olympic Committee. “I worked with elite athletes, and I noticed they drank a lot of caffeinated beverages without showing any sign of dehydration,” she says. In 2000, she published a study in the Journal of the American College of Nutrition showing that the body doesn’t discriminate between regular and decaf beverages when it comes to hydration.

MYTH: If you’re thirsty, you’re already dehydrated. TRUTH: While thirst is an accurate barometer of when to imbibe, the notion that thirst signals a dehydrated body is not true, says Valtin. Thirst is triggered when the blood’s concentration of solid particles rises by 2 percent. Dehydration occurs when the blood concentration rises by 5 percent. So, thirst sets in before dehydration and people who shrug off their thirst can find themselves on the path to dehydration. “Thirst is the first indicator of the body’s need for water,” cautions Dee Sandquist, a spokesperson for the American Dietetic Association. Signs to watch out for include headache, dry mouth, rapid pulse and lightheadedness.

MYTH: Urine should be clear. TRUTH: Perpetually clear urine can actually be a sign of drinking too much water, which can dilute the body’s electrolytes, according to Grandjean. “Healthy urine should have some color,” she counsels. Certain vitamins, such as riboflavin (B2), can darken urine.

MYTH: Drinking a lot of water suppresses the appetite. TRUTH: While being adequately hydrated helps the metabolism run at its optimal level, drinking vast quantities of water won’t affect the overall amount of food you eat. Because water quickly empties from the stomach, drinking water has little effect on appetite, says Barbara Rolls, director of the Laboratory for the Study of Human Ingestive Behavior, at Pennsylvania State University. Eating foods that have a high water content, such as fruits, vegetables, soups and grains, can help us to feel sated.

MYTH: Bottled water is always better than tap water. TRUTH: Not necessarily. Be aware that bottled water is often just tap water. A Natural Resources Defense Council report cites government and industry findings that 25 percent of bottled water is plain tap water; sometimes treated, sometimes not. NSF International certification indicates brands that meet federal safety standards.

Catherine Guthrie is an award-winning health and lifestyles journalist in Bloomington, IN. Connect at CatherineGuthrie.com.