A global study challenges the eight-glass-a-day water rule, revealing individual water needs vary widely based on age, diet, and activity levels.
Study challenges eight-glass-a-day rule
A study published in Science in November 2022, led by Yosuke Yamada and John Speakman, measured the actual water turnover in the human body across 5,604 people from 23 countries. Common guideline lacks scientific support
The commonly cited guideline of drinking eight glasses of water per day, or approximately two liters, lacks solid experimental evidence and is largely attributed to commercial marketing efforts, according to the researchers. Water needs vary by individual factors
The study found that water needs vary significantly among individuals, influenced by factors such as diet and energy expenditure. On average, men aged 20 to 35 have a water turnover of 4.2 liters per day, while women aged 20 to 40 have a turnover of 3.3 liters. Water turnover declines with age
These figures decline with age, reaching approximately 2.5 liters by the age of 90. The study used deuterium-labeled water to track water turnover, a method considered the gold standard for measuring hydration levels. Energy expenditure, not thirst, determines needs
The researchers emphasize that factors other than thirst, such as energy expenditure, play a more significant role in determining water needs.
