What is the Daily Intake Formula for Water for Optimum Health?

"The science has never supported eight glasses as an appropriate guideline, if only because it confused total water turnover with water from beverages, and a lot of your water comes from the food  you eat."

"This work is the best we've done so far to measure how much water people actually consume on a daily basis -- the turnover of water into and out of the body -- and the major factors that drive water turnover."

Dale Schoeller, professor emeritus, nutritional sciences, University of Wisconsin-Madison

There is no formal recommendation for a daily amount of water people need.   Credit...Todd Heisler/The New York Times

An American nutritionist, Dr. Fredrick J. Stare, suggested in 1974 that six to eight glasses of water daily would represent an optimum liquid intake for people's health. He did add that other drinks and food should be accounted for, within that six to eight glasses of water daily. He was thought to have been the originator of what  became in time a wildly popular and widely accepted basis for fluid intake for the human body.

It is entirely possible that many people have the impression that the more water one drinks for a daily intake, the healthier they will be. In fact, blood sodium content too diluted by the intake of too much water stands the risk of triggering hyponatremis, a potentially life-threatening condition. So common-sense is called for in extreme reactions to any situation. And water intake is entirely situational.

 

Researchers have now studied thousands of people in 26 countries to determine how much water is needed and in the process discovered that there is great variation; water requirements for each individual is not summed up in a generalized 8-glass-a-day formula. It was found that daily averages including water derived from other sources such as food and other types of liquid, ranged from one to six litres per day.

Test subjects in previous studies were asked to self-report their water intake. This study instead measured water as it moved throughout the body. Water containing hydrogen and oxygen isotopes was given to participants so the water could be tracked as it moved through their bodies. Published in the journal Science, the results found amounts required was entirely dependent on temperature, gender and activity levels.

Around 3.2 litres daily was determined to be the ideal water intake of an 154-pound man of age 20 living at sea level in a developed country with a mean air temperature of 50F, with average physical activity. A woman of the sage age weighing 125 pounds whose activity in the same geographic area was average had a requirement of 2.7 litres. While a 112 pound person would need 2.5 litres daily, and an individual weighing 210 pounds would need five litres.

Doubling daily energy expenditure would see the same people requiring an additional litre, according to the researchers. A further 0.3 litres a day would be needed with a 50 percent increase in humidity, to remain properly hydrated.