New research has found that two litres - or eight glasses of water - a day might be too much for most people.
In fact, people can have a wide range of water intake requirements, with many only needing around 1.5 to 1.8 litres per day, according to researchers at the University of Aberdeen. Among other factors, this is because we get a good amount of water from the food that we eat.
Some 3.6 litres of water comes from food for a typical person, meaning that they need less than two litres of drinking water each day. This can vary depending on sex, age and the climate that you live in among other factors.
The researchers at the Scottish university, which teamed up with Scientists from institutions from around the world, analysed water intake for 5604 men and women, aged between eight days and 96 years old, from 23 different countries.
Participants drank a glass of water which replaced some of the hydrogen molecules with deuterium - a completely harmless stable isotope of hydrogen. The rate in which the extra deuterium was eliminated shows how quickly the body is turning over water.
men aged 20 to 35, turned over an average of 4.2 litres per day while Women aged 20 to 40 averaged a turnover of 3.3 litres.
Professor John Speakman from the University of Aberdeen School of Biological Sciences, explains: "Water turnover is not equal to the requirement for drinking water. Even if a male in his 20s has a water turnover of on average of 4.2 litres per day, he does not need to drink 4.2 litres of water each day.
"About 15% of this value reflects surface water exchange and water produced from metabolism. So the actual required water intake is about 3.6 litres per day. Since most foods also contain water, a substantial amount of water is provided just by eating."
He added that the varying water contents of foods makes it difficult to work out the exact required amount. Professor Speakman said that a "one size fits all policy" of eight glasses for water intake is not supported by scientific research.
The research was published in Science this week on November 25.
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