Scientists have canceled the rule of eight glasses of water a day

Many of us are guided by the idea that we need to drink at least two liters of water every day. However, a new study by an international team of scientists, published in the journal Science, shows that there is no standard water intake. Moreover, eight glasses of water a day for most people is too much, according to The Guardian.

“The well-known recommendation is not scientifically supported at all”, - says Yosuke Yamada, one of the authors of the article, from the Japanese National Institute of Biomedical Innovation, Health and Nutrition. Most scientists don't know where it came from. If you only eat bread, bacon, and eggs, you won't get much water from food, but if you eat meat, vegetables, fish, pasta, and rice, then 50% of your total fluid intake comes from food".

The study participants were 5604 people from 23 countries aged from eight days to 96 years. They were given a glass of water to drink in which some of the hydrogen molecules had been replaced by a stable isotope of the element deuterium. It is a harmless compound found in the human body. The rate of excretion of additional deuterium indicates the rate of water metabolism in the body. It turned out that it varies greatly depending on age, gender, the level of human activity and the state of the environment. Those who live in hot and humid climates and at high altitudes, as well as athletes, pregnant and lactating women, excrete water faster, which means they need to drink more.

The most important thing is energy consumption. It is highest in men between the ages of 20 and 35, who require an average of 4.2 liters of water per day. With age, this figure decreases. Women aged 20-40 have an average water turnover of 3.3 liters. However, this does not mean at all that we need to drink 3-4 liters of water. Approximately 15% of the fluid in the body is a product of water exchange as a result of metabolism. Most foods also contain water.

"The common belief that we should all drink eight glasses of water is probably too much for most people in most situations", - the study authors summarize. Calculations show that a typical middle-aged man needs to drink 1.6 to 1.8 liters per day, and a typical woman of the same age - 1.3 to 1.4 liters. For people over 80, the norm can be approximately 1.1 liters per day. But a lot of it depends on how liquid you eat.