The water turnover equation predicts the daily water demand of the human body

Is it really scientific to drink eight glasses of water (about 2 liters) a day for good health? Recently, a study published in the journal Science has subverted people's previous perception of drinking water, arguing that the above drinking water recommendations may exceed the real water
needs of most people.

In this study, the team of 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 (preparation), together with nearly 100 international teams, studied a total of 5604 subjects in 26 countries based on the stable isotope method, with a sample age ranging from 8 days old infants to 96-year-old people, and derived the world's first formula for predicting the daily water demand of the human body.
For the first time, the law
of water demand throughout the human life cycle was revealed.

"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.
Speakman said
.

Different groups of people have different water needs

Without water, humans can only survive for 3 days
.
The daily water turnover of the human body is the total exchange of water, including the water ingested and the water lost, which largely reflects people's water
needs.

The Spikman team and the international team, based on the international "double standard water" database, used deuterium dilution technology to measure the water turnover rate 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 water turnover is not equal to the water
demand for drinking water.
For example, a man in his 20s who has a daily water turnover of 4.
2 liters does not need to drink 4.
2 liters of water, because human metabolism and surface water exchange provide 15% of this, and the remaining 85% of water needs come from food and water, half of food and water, 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.

"One of the main results of the study is that the recommended amount of drinking water of 8 glasses of water per day (or about 2 liters per day) is probably too high for most people
.
" Zhang Xueying, assistant researcher at Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences and co-first author of the paper, said
.

In addition, studies have found large individual differences in water turnover
.
For example, among 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 much as 20%.

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

There is a new basis for the development of drinking water and water-rich food management programmes

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 used deuterium dilution technology to objectively and accurately measure the water turnover of the subjects, 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 the water turnover rate throughout the human life process
.

The analysis found that people living in hot, humid environments and high altitudes, as well as athletes, pregnant and lactating women, and people with high levels of physical activity, had higher
water turnover.
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 the formulation and improvement of future management plans for drinking water and water-rich foods.

"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.
" Speakman said
.
At present, the Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, has established the first "double standard water" laboratory and precision human nutrition laboratory in China, which will further reveal the laws of life and provide scientific guidance
for human beings to formulate precision nutrition strategies.

China Food News(Version 07, December 19, 2022)

(Responsible editor: Luo Chen)