The Speakman team of the Shenzhen Advanced Institute of the Chinese Academy of Sciences revealed for the first time the law of water demand throughout the life cycle of human beings

There is often a saying circulating on the Internet that drinking eight glasses of water (about 2 liters) a day is good for good health, is this really scientific?

On November 25, Beijing time, a study published in Science subverted people's previous perception of drinking water, and the above drinking water recommendations may exceed the real water
needs of most people.

In this study, Academician John Roger Speakman, Chief Scientist of the Energy Metabolism and Reproduction Research Center of the Institute of Medicine, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, and Chair Professor of the School of Pharmacy of Shenzhen University of Technology The team united nearly 100 international teams to study a total of 5604 subjects in 26 countries based on the stable isotope method, with samples ranging from 8-day-old infants to 96-year-old people, deriving the world's first formula for predicting the daily water demand of the human body, revealing for the first time the water
demand law of the whole life cycle of human beings.

This is the second important result
published in Science after Speakman and the international team first revealed the laws of human life cycle metabolism in Science in 2021.
In the study, Academician Speakman is the main corresponding author of the paper, and Zhang Xueying, assistant researcher of Shenzhen Advanced Institute, is the co-first author
of the paper.

Screenshot of the article going live

Link to the paper: style="font-family: ; font-size: 14px; white-space: normal; background-color: rgb(248, 249, 244); text-indent: 2em;" _msthash="101744" _msttexthash="86203858">"Understanding the factors that influence water turnover and the relative importance of each is a big step
forward in projecting future water demand.
This work builds on contributions from scientists from around the world and demonstrates the importance of
international scientific collaboration in answering major scientific questions.
Academician Speakman, the corresponding author of the paper, said
.

Subvert the "8 glasses of water a day" perception

Water is the source
of life.
Without water, humans can only survive for three days
.
The daily water turnover of the human body (Water Turnover) is the total exchange of water, including the water we ingest and the water we lose, which largely reflects people's water
needs.

Speakman's team and international team, based on the international "double standard water" database, used deuterium dilution technology to measure the water turnover of the subjects, and found that the daily water turnover of men aged 20~35 was 4.
2 liters, and the daily water turnover of women aged 30~60 was 3.
3 liters, and then decreased with age, and fell to about 2.
5 liters in their 90s
.

It is worth noting that the turnover of water is not equal to the water demand of drinking water, for example, a man in his 20s has a daily water turnover of 4.
2 liters, but does not need to drink 4.
2 liters of water, because human metabolism and surface water exchange can provide 15% of it, and the remaining 85% of water demand comes from food and drinking, food and drinking water are halved, so the average daily water intake of men in this age group is 1.
5-1.
8 liters
.

In contrast, women drink less water because women have a lower non-fat component than men, such as a woman in her 20s, who may drink 1.
3-1.
4 liters
of water per day.

"A major result of the study is that the recommended amount of 8 glasses of water (or about 2 litres per day) we should all drink may be too high for most people
.
" Zhang Xueying, co-first author of the paper, said
.

In addition, studies have found large individual differences in water turnover, for example, in adults alone, some people have a daily water turnover of only 5% of their body water, while others have a water turnover rate of as high as 20%.

People of different ages, genders, and countries have different water needs
.
Therefore, this one-size-fits-all health advice is not suitable for precise health guidance
for individuals.

Reveal the law of water demand throughout the life cycle and predict future water demand

Since the 80s of the 20th century, the "double standard water" method is the "gold standard"
for detecting the energy consumption of the human body in a free living state by collecting the subject's urine for 14 days and analyzing the changes in the abundance value of the markers.

Academician Speakman is an authority on "double standard water" technology, and he is also an academician of many countries and academies (foreign academician of the Chinese Academy of Sciences, foreign academician of the American Academy of Sciences, academician of the Royal Society, academician of the European Academy of Sciences).
He led the management and use of the international "Double Standard Water" database, and produced a number of major scientific discoveries
on this basis.

"Every aspect of the paper from submission to publication was challenging, and the integration of the double standard water database and the ambient temperature database was the biggest challenge, and we are very fortunate that we successfully overcome these challenges
.
" Zhang Xueying recalled
.

Zhang Xueying introduced that in past studies, most of the research on human water demand relied on subjective questionnaires and physiological studies in the laboratory, with small sample sizes and imprecise
assessment methods.

The research team objectively and accurately measured the water turnover of subjects by using deuterium dilution technology, and studied the influence of factors such as weight, age, body composition, total energy expenditure, physical activity level, as well as climate, latitude, altitude, temperature and humidity on water turnover throughout the human life process
.

The analysis found that water turnover was higher
in people living in hot and humid environments and high altitudes, as well as among athletes, pregnant and lactating women and people with high levels of physical activity.
In addition, higher water turnover rates were observed in developing countries and in populations engaged in heavy physical work; Daily physical activity also increases water turnover
.

In addition, the study mentioned that water turnover has been shown to be related to many physiological health indicators, such as physical activity level, body fat rate, etc.
, and for the first time proposed the concept that water turnover can be used as a new biomarker reflecting human metabolic health, which provides new ideas
for the study of various metabolic chronic diseases such as obesity and diabetes.

Based on the influence of the above factors on water turnover, researchers developed the world's first equation for predicting human water turnover
.
"This equation can be applied to countries and regions around the world, and only need to understand a person's basic physiological indicators and the average temperature and humidity of the living environment to predict a person's water
demand.
" Zhang Xueying introduced
.

With the change of world population structure and climate warming, this study provides the equations used to predict human water demand under the guidance of large data sets, and provides an important scientific basis
for future management plans for drinking water and water-rich food improvement.

"Water is necessary for life, water turnover is closely related to water demand, and this study has taken the first step
to build a personalized predictive water turnover algorithm.
" Academician Speakman said
.
At present, the Shenzhen Advanced Institute where Academician Speakman is located has established the first "double standard water" laboratory and precision human nutrition laboratory in China, which will further reveal the law of life and provide scientific guidance for human beings to formulate precision nutrition strategies
.

Schematic diagram of water turnover Source: Photo courtesy of the research team

Academician Speakman (left), corresponding author of the paper, and Zhang Xueying, co-first author of the paper (right) Source: Photo courtesy of Shenzhen Advanced Institute