How much water is the healthiest thing to drink every day? There is a formula to calculate

In life, "thirst" is usually a signal to remind us to drink water. When the body is dehydrated, the osmotic pressure of the extracellular fluid increases, and the thirst receptors in the hypothalamus are stimulated, which will cause the feeling of thirst. This means that when you feel "thirsty", your body is actually dehydrated. The more dehydrated you are, the more severe the feeling of thirst will be.

However, there is no definite number for how much water a person should drink in a day. The human body takes in water mainly by drinking directly and eating various foods, and metabolizes water mainly through sweating, urinating, breathing, etc. As long as the total amount of water input and loss is balanced, the human body will not be dehydrated.

Water turnover is an indicator of the daily water requirement of the human body. Researchers usually use isotope labeling to observe the metabolic activity of water in the human body. During the experiment, participants drank water containing the hydrogen isotope "deuterium", which is commonly known as "heavy water". This water can participate in human metabolic activities normally, is non-radioactive, and is very safe. Researchers can track and observe the whereabouts of deuterium in the human body, so they can know where the water people drink goes, and thus calculate the water turnover.

The picture comes from Tuchong.com

In a paper published in 1993, researchers used isotope labeling to measure 171 children aged 6-15 and found that both boys and girls had a lower water turnover as they aged. In addition, the water turnover of these children was higher than that of sedentary urban white-collar workers.

A study in 2022 further explored the water needs of different people. The researchers selected 5,604 volunteers from 26 countries, and the age range was very wide, ranging from 8-day-old babies to 96-year-old seniors.

Through isotope labeling, researchers found that the energy consumption of the human body and whether or not the person is an athlete are most closely related to water turnover. Gender, age, and the economic development level of the country of residence will also affect water turnover. Based on relevant data, researchers roughly estimated that a healthy adult male needs to consume an average of 2.7L of water per day. After taking into account the water contained in food, which is about 20%-50%, he still needs to drink about 1.35L-2.16L of water per day.

Of course, this does not mean that you have to abide by this number to drink water. In fact, researchers have summarized a very complex formula to calculate the daily water requirements of different people. If you are interested, you can also use this formula to calculate how much water you need every day.

PAL: Physical Activity Level, PAL = total energy expenditure of the human body in 24 hours / basic energy expenditure of the human body in 24 hours

Weight: kg

Gender: 1 for male, 0 for female

Humidity: local air humidity, unit: %

Athlete status: 1 for athletes, 0 for non-athletes

HDI: Human Development Index, "high" is 0, "medium" is 1, "low" is "2", and China is "high"

Altitude: m

Age: year

Temperature: local temperature, unit: ℃

This article is a work supported by Science Popularization China Starry Sky Project

Author: The Nutcracker

Review: Tao Ning

Produced by: China Association for Science and Technology Department of Science Popularization

Producer: China Science and Technology Press Co., Ltd., Beijing Zhongke Xinghe Culture Media Co., Ltd.