For ages, we have been told and taught that the human body needs at least 8 glasses of water daily to function properly. However, a recent study has stated that this long held belief has inadequate scientific backing.
From the University of Wisconsin, USA, the researchers of the study found that water requirements of the human body vary based on individual factors, such as age, gender, physical activity level, and climate. Simply put, the findings indicate that a one-size-fits-all approach to water consumption may be wrong.
The study, published in Science Journal, involved over 5,600 participants across 26 countries.
To measure water turnover more accurately, researchers gave participants 100 millilitres of water enriched with 5 percent ‘doubly labelled water’.
“Doubly labelled water is often used for metabolism experiments as it provides a way to track how rapidly chemicals are moving through the body.
“This type of water contains isotopes of hydrogen and oxygen that can track water and energy metabolism in the body.
“If you measure the rate a person is eliminating those stable isotopes through their urine over a week, the hydrogen isotope can tell you how much water they’re replacing, and the elimination of the oxygen isotope can tell us how many calories they are burning,” said Dale Schoeller, a nutritional scientist and lead author of the study
According to the team, this method, pioneered in the 1980s at the same University of Wisconsin–Madison, offers a more precise result when compared to earlier studies which relied on self-reported data.
“This study indicates that one size does not fit all for the drinking water guideline.” Schoeller stated.
The findings revealed that water turnover is highest in newborns, who replace about 28 per cent of their body’s water daily, and decreases with age. Men aged 20–30 and women aged 20–55 showed the greatest water turnover rates, which declined after 40 in men and after 65 in women.
It also highlighted that environmental and physiological factors also influenced water needs.
Explaining further, Schoeller said, “For example, a sedentary 20-year-old man weighing 70 kg in a temperate climate requires about 3.2 litres daily, while a woman of the same age and weight needs approximately 2.7 litres daily.
“Increased activity, body weight, or humidity levels significantly raised water turnover, with some highly active individuals consuming over 7–10 litres daily.”
The study also noted increased water requirements during the third trimester of pregnancy and breastfeeding, as well as among manual labourers and hunter-gatherers compared to those in sedentary, temperature-controlled environments.
The researchers emphasised the importance of updating water intake guidelines to reflect individual and environmental differences.
“Improved guidelines are of increasing importance because of the explosive population growth and climate change the world currently faces, which will affect the availability of water for human consumption,” the study finds