Do you aim to chug eight glasses of a water every day? You may not need to.
The recommended intake of two litres of water a day could be too much, new research from the University of Aberdeen shows.
Given around half of our daily intake of water comes from food, scientists estimate we only really need around 1.5 to 1.8 litres per day.
Research in this area previously depended on surveys applied to small samples of people, but scientists have now collaborated across the world to measure water turnover.
Though experts such as the European Food Safety Authority (EFSA) recommend an adequate total daily water intake of two litres, the study found this is likely too high for most people in most situations and a ‘one size fits all’ policy for water intake is not supported by the research data.
More than 5,600 people aged 8-96 from 23 different countries were involved in the study, making it the largest of its kind. Scientists analysed participants’ water turnover, the total intake and water loss movement of the body, which is closely related to our water requirement.
The study, published in in the journal Science, involved people drinking a glass of water in which some of the hydrogen molecules were replaced by a stable isotope of the element called deuterium, which is found naturally in the human body and is completely harmless.
Those living in hot and humid environments and at high altitudes as well as athletes, pregnant and breastfeeding women need more water, as the research showed water turnover is higher among them.
Energy expenditure is the biggest factor in water turnover, with the highest values observed in men aged 20-35, who turned over an average of 4.2 litres per day. This decreased with age, averaging 2.5 litres per day for men in their 90s.
Women aged 20-40 averaged a turnover of 3.3 litres, which also declined to 2.5 litres by the age of 90.
Water turnover is not equal to the requirement for drinking water, Professor John Speakman from the University of Aberdeen shared.
“Even if a male in his 20s has a water turnover of on average of 4.2 litres per day, he does not need to drink 4.2 litres of water each day,” Speakman explained. “About 15% of this value reflects surface water exchange and water produced from metabolism.
Professor Lewis Halsey from the University of Roehampton London added: “Water is essential for human survival and measuring our exact water requirements continues to remain a challenge.
“This research sheds light as to how factors including climate, age, physical activity, pregnancy and water intake of food can determine how much water intake we actually need.”