Water needs vary widely from person to person, shattering once and for all the entrenched myth that we should all drink at least eight glasses of water a day to stay healthy, claims a new international study.
Researchers have measured for the first time how much water is actually expended, and then replaced, every day by thousands of humans.
They studied 5,600 people from 26 countries, ranging in age from eight days to 96 years. They found that daily averages fluctuated between one liter and six liters of water.
This allows for the very first time to paint a real portrait of human water consumption, commented Professor Stéphanie Chevalier, of the School of Human Nutrition at McGill University.
“These are data of immense quality that are not approximate,” she said. We have real data to then build recommendations based on all their analyses, so for that, it’s very interesting. »
This study would be the first ever not to rely on participant-provided information to measure their water consumption, which can generate data of questionable utility. Instead, the new research objectively measured how long the subjects took to pass out water to which oxygen and hydrogen isotopes had been added to make it detectable in their urine.
More than 90 researchers contributed to this work. They found that, among their subjects, water replacement peaked in their twenties for men, and was fairly stable for women between the ages of 20 and 55. However, it is the newborns who come in first place, since they replace an average of 28% of the water in their bodies every day.
All other things being equal, men replace about half a liter more water each day than women.
If this study is not revolutionary in the world of nutrition, we can hope that it has at least the effect of reminding people that the myth of “eight glasses of water a day” is nothing other than that ― a myth, said Ms. Chevalier.
“When I read this, my hair always frizzles a little because I think to myself, how can anyone think that, for example, an eighty-year-old lady who weighs 50 kilos should drink eight glasses of water, same amount as a big guy of 30 who works on a construction site outside all day? “, did she say.
In general, said Ms. Chevalier, people are recommended to consume one milliliter of water per day for each calorie burned. In other words, an individual who expends 2000 calories in a day should also drink two liters of water.
The researchers also found an association between water consumption and the UN Human Development Index of participants’ countries: the lower the country’s index, the higher the water consumption, possibly because it These are frequently hot countries where air conditioning is non-existent and whose inhabitants have to work very hard physically to survive.
The authors of the study point out that, in the face of climate change and the constant growth of the human population, more and more people are at risk of not having enough drinking water to meet their needs. They therefore consider that their results could help to more accurately predict the water needs of the population.
The findings of this study were published by the prestigious journal Science.