How Much Water Should You Drink a Day? Not Two Litres?

Last Updated on March 14, 2023 by Ecologica Life

Bye bye to the 2 litres or eight daily glasses of water. Scientists are now stating that this one size fits all recommendation is redundant. A new study carried out with thousands of people reveals that not everybody has the same need to drink the same amount of water. The report published in Science finally brings an end the repetitive belief of eight daily glasses.

The study measured the amount of water people actually consume on a daily basis – the turnover of water in and out of the body – and the main factors that drive it.

Each Person Should Drink What Water They Need

The results do not indicate new patterns. Rather, they reflect that there are a set of physical, atmospheric, and genetic conditions that make us drink more or less.

The study measured the water turnover of more than 5,600 people from 26 countries, ranging in age from 8 to 96, and found that there were daily averages from 1 litre per day to 6 litres per day. “There are also outliers that bill up to 10 litres a day,” Adds Schoeller, co-author of the study.

The new research objectively measured the time it took for water to circulate through the body of study participants by following the rotation of “labelled water.”

Study subjects drank a measured amount of water containing traceable isotopes of hydrogen and oxygen. Isotopes are atoms of the same element that have slightly different atomic weights, making them distinguishable from other atoms of the same element in a sample.

Participants’ environmental characteristics, such as hometown temperature, humidity, and altitude, were compared to measurements of water turnover, energy expenditure, body mass, sex, age, and athletic status.

The researchers found that the volume of water turnover peaked in men during their 20s. While the women maintained a plateau from their 20s to 55 years. New-borns however are the ones that renew the most water daily, replacing around 28% of their body water.

Exercise is One of The Key Factors

The level of physical activity and sports status explain most of the differences in water turnover, followed by sex, the Human Development Index and age.

When conditions are equally the same, men and women differ by about half a litre of water renewal. As a baseline, the study results predict that a 20-year-old non-athlete (but with average physical activity) man who weighs 70 kilos and lives at sea level in a developed country with an average air temperature of 10 degrees C and a relative humidity of 50%, ingests and loses about 3.2 litres of water per day. A woman of the same age and activity level, weighing 60 kilos and living in the same place, would use 2.7 litres.

The researchers found that if a person’s energy use is doubled, their daily water consumption will increase by about a litre. Fifty kilos more of body weight adds 0.7 litres a day. A 50% increase in humidity increases water consumption by 0.3 litres. Athletes use approximately one litre more than non-athletes.

Double energy use means an extra litre of water per day

The researchers found that “hunter-gatherers, mixed farmers, and subsistence farmers” had higher water turnover than people living in industrialized economies. In short, the lower the Human Development Index of your country, the more water you use per day.

Farmers and ranchers from developing countries are the ones who use the most water per day.

“That’s representing the combination of several factors,” Schoeller says. “Those people in low HDI countries are more likely to live in areas with higher average temperatures, more likely to be performing physical labour, and less likely to be inside in a climate-controlled building during the day. That, plus being less likely to have access to a sip of clean water whenever they need it, makes their water turnover higher.”

Understanding Drinking Water Requirements is Vital

“Determining how much water humans consume is of increasing importance because of population growth and growing climate change,” says Yamada, one of the 90 researchers involved in the study. “Because water turnover is related to other important indicators of health, like physical activity and body fat percent, it has potential as a biomarker for metabolic health.”

How My Water Drinking Habits Affect the Environment

As it is clear from this article, every person’s needs for daily water are different, depending on who you are, where you are and what you do. It is therefore important that you drink the amount of water you feel you need, not too much and not too little. Listen to your body, it will let you know.

As far as the environment goes, drinking tap water is much more environmentally friendly than bottled water. Bottles water is apparently 3500 times worse for the environment than tap water according to scientists. So consider drinking tap water where possible.

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