Is 6-8 Glasses of Water a Day Enough?

Very few people will argue that we don’t need to drink at least 6-8 glasses of water a day. The research is already in.

Water is necessary for practically all of our body’s metabolic functions. The body can survive for months without food. Water is a more urgent need.

There are many symptoms of dehydration. Many of these are sub-clinical – they aren’t readily observed. Many symptoms of dehydration are also misdiagnosed.

Research supporting need for adequate water

A 2002 study involving 20,297 people found those who drank at least five glasses of water a day were 41% less likely to develop fatal coronary artery disease.

A 1999 Harvard study of 47,909 health professionals showed that six cups of water per day reduced the risk of bladder cancer by over 50%.

A 2009 study of 58 children showed that those who drank more water performed better on cognitive tests. And there’s more.

How much water is needed?

In 2004, the National Academy of Sciences released a study showing that the average woman needs about 91 ounces of water per day and the average man needs about 125 ounces per day. The report indicated that about 20% of hydration can come from a typical diet, leaving 73 ounces of water for the average adult woman and 100 ounces of water for the average adult man. That’s a lot more water than the adage of 6-8 glasses a day (48-64 oz).

Fluid loss

Dr. Jethro Kloss studied water use and fluid loss in the 1930’s.

He found that every day the average person loses about 550 cubic centimeters of water through the skin, 440 cc through the lungs, 1550 through the urine, and another 150 cc through the stool.

This adds up to 2650 cc per day in fluid loss, equivalent to a little over two and a half quarts (about 85 fluid ounces). He wasn’t too far off.

For references to the above studies, more research and information on water – including filtration, water treatment, chlorination and water pollution, see Pure Water: The Science of Water.