The common advice is to drink 6-8 glasses of water every day, but some experts say not everyone needs to "count their cups"

Medford/Somerville, Mass. [06.29.01] -- As the summer heats up around the country, many Americans beat a well-worn path to the water cooler to avoid dehydration. But are all those trips necessary? While the basic rule of thumb suggests drinking six to eight glasses every day to stay safe, some experts say not everyone needs to fill up with so much water.

   According to Tufts University's Harry Bernheim, the body is constantly losing water -- not just by sweating and trips to the bathroom, but with every breath.

   "Our bodies saturate the air we breathe with water vapor, because we don't want our lungs to dry out," the biology professor told U.S. News and World Report this week.

   But most people replenish that supply pretty easily, he said.

   "People have evolved over time to keep themselves hydrated," Bernheim said.

   He explained that many people get enough body fluids through the foods and drinks they eat during meals to satisfy half of their daily needs.

   "If you're not exercising or outdoors in the heat, you can often get the fluids you need without counting cups," reported the news magazine.

   If you are exercising, Bernheim suggested, bring extra water.

   "If it's a really hot day and you're sweating a lot, you better be replacing those fluids," he told U.S. News.

   But not all at the same time.

   "Avoid drinking large amounts at once -- your kidneys will quickly flush the excess fluid and send you to the bathroom," the magazine reported.

Photo of by Adam Hart Davis