The common recommendation is to drink eight glasses of water a day, says Tamara Hugh Butler, an exercise scientist at Wayne State University, emphasizing that the idea is a myth.
She added that factors such as body size, outside temperature, difficulty breathing and sweating will determine how much water we need.
She stressed that the amount of water we need each day also depends on our health, noting that people with conditions such as heart failure or kidney stones need different amounts of water than those who take diuretics.
In contrast, Dr. Töpf explains that, for most healthy young people, the best way to stay hydrated is to simply drink water when thirsty.