Drinking eight glasses of water - do you even need it?

To drink eight glasses of water in a day is advice every single person has been given at some point or the other. But is the “one size fits all” idea actually a fact or just a myth?

A recent study published in academic and scientific journal Science showed people could be drinking more water than needed and that the daily requirement could vary from person to person.

BBC cited the study, in which scientists from the University of Aberdeen discovered that the suggested two litres could actually be much higher than the human body requires on average.

As per the study, the estimated amount of water people really need daily is 1.5 to 1.8 litres as a lot of water comes from food and other intake.

"The original estimate of two litres a day comes from a slight miscalculation. The water that we would need to drink is the difference between the total water that we need to ingest and the amount that we get from our food," BBC quoted Prof John Speakman from the University of Aberdeen as saying.

The scientist said that asking people how much they eat is a common practice to estimate the amount of water intake that comes from food. He, however, said that following this method could result in misestimation as people "under-report" the amount of their food intake.

Why findings of this study could be true

There have been countless studies to find the correct answer to the question but the surveys applied to small samples of people. However, this new study was conducted through collaboration across the globe, in which scientists used a stable isotope technique.

The survey involved 5,604 individuals aged between eight days and 96 years old, from 23 different countries. Some of the hydrogen molecules were replaced by a stable isotope of the element called deuterium in a glass of water the participants of the survey consumed.

Deuterium is an element naturally found in the body so the rate of its elimination showed how quickly the water in the body turned over.

It was discovered that people with a higher water turnover generally need to drink more water, while energy expenditure is the biggest factor in water turnover.

'Drinking more water is just an adage'

Meanwhile, CNN’s senior medical correspondent Elizabeth Cohen said that drinking more than needed water is just “an adage” and does “no harm” to the human body.

When asked how much water should people drink, Cohen said that people only need to observe the colour of their urine instead of counting the glasses of water they consume, to see if they are drinking enough water.

As per the study, a person is considered healthy and hydrated if the colour of their pee is pale straw. The “amber or honey” coloured urine indicates mild dehydration while “syrupy or brown ale” coloured pee shows that a person is experiencing “worrisome dehydration” which could be a sign of liver disease.

She said that the symptoms are well known in a country with hotter weather. 

“If you’ve yellow pee, that’s not good," she translated an Israeli song, saying that everyone needs to learn that.