This report I heard on the news yesterday. I thought it was an interesting test concerning the amount of water to drink.
Tanya
http://tv.ksl.com/index.php?nid=44&sid=7033
U of U Researchers Test Water Theory
Jan. 22, 2003

There's been a lot of controversy over how much water people should drink. Now researchers at the University of Utah are putting water to the test.

Drinking water is part of good health. But just how much do you need?

Some have criticized the old rule of thumb-- eight eight-ounce glasses a day-- saying there's no scientific proof.

But that's changing. Doctor Wayne Askew is director of the Division of Foods and Nutrition at the University of Utah.

He says, "We wanted to do a study to see if we could detect any measureable difference in human physiological measurements that would relate to how much fluid they drank over a relatively wide range of fluid intakes."

In a series of experiments, a group of volunteers drank four, eight, or 12 eight-ounce glasses of water a day. They followed a set diet and had specific exercise limits.

On the morning of the fifth day, before getting up out of bed, the volunteers were all hooked up to a machine which calculated how many calories they burned per minute, during a true resting state. They also had blood tests and urine tests done to measure their level of hydration."

Dr. Askew says, "There was a definite difference in the things that scientists look at to determine how well you are hydrated with respect to how much fluid you drink. And the groups that drank four showed they were definitely not as well hydrated as the group that drank eight or 12."

What's more, the groups drinking just four glasses a day burned slightly fewer calories, their metabolism was less efficient. And that's not all.

"They felt much better drinking the eight and the 12, than they did the four. Their ability to concentrate, they felt was better, their energy level was better, and they felt more like exercising."

The bottom line-- it seems the old eight-by-eight is a good rule of thumb after all.

"Its going to take care of most people. Some people may not need that much, and some people might need a little bit more. But as a general rule, it's not too bad."

The next step is to look at people who are more active, exercising more, sweating more.

The temperature, the relative humidity, your body size, whether you're old, whether you're young, whether you're lactating, wherether you're pregnant-- these things all influence water requirements.