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Health & Balance

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Water, Water, Everywhere.

How Much Water Do You Really Need to Drink?

Myth No. 2: Caffeinated beverages make you dehydrated

Not true.

"For years, newspaper and magazine articles have repeated the notion that caffeine is dehydrating as if it's absolute fact," says University of Nebraska researcher Ann Grandjean, EdD. But in a study published in the October 2000 Journal of the American College of Nutrition, Grandjean and her colleagues at the Center for Human Nutrition showed that it's pure fantasy.

The researchers looked at how different combinations of water, coffee, and caffeinated colas affected hydration levels in a group of 18 men between the ages of 24 and 39. During one phase of the experiment, the only fluid the volunteers consumed was water. During another, 75% of their intake was caffeinated.

"Using almost every test ever devised to measure dehydration, we found no difference at all," says Grandjean.

Myth No. 3: By the time you feel thirsty, you're already becoming dehydrated

Maybe if you're an elite athlete running a marathon or a hotshot tennis player sweating in the noonday sun -- but not if you're going about your everyday activities.

Thirst is, in fact, a very sensitive mechanism for regulating fluid intake, according to Barbara Rolls, PhD, a nutrition researcher at Pennsylvania State University. In a 1984 study in Physiology and Behavior, she and a group of colleagues at Oxford University followed a group of men as they went through their normal day. Left to their own devices, the volunteers became thirsty and drank long before their hydration levels showed any signs of dipping.

Says Rolls, "If people have access to water or other fluid beverages, they seem to do a very good job of maintaining hydration levels."

Myth No. 4: Drinking plenty of water can help you lose weight

This idea makes sense, since water contains no calories. The trouble is, drinking a glass of water doesn't do anything to take the edge off hunger.

"Water sneaks right past without triggering satiety signals, the cues that tell your body when you're full," says nutritionist Barbara Rolls, author of Volumetrics.

Surprisingly, adding water to the food you eat, on the other hand, does seem to tame hunger. In a study reported in the October 1999 American Journal of Clinical Nutrition, Rolls found that women who eat a bowl of chicken soup feel fuller than those who eat chicken casserole served with a glass of water, even though both meals contain exactly the same ingredients. The soup eaters also tended to be less hungry at their next meal -- and to eat consume fewer calories -- than those who ate the casserole.

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