Drink at least two liters of water a day! How many times have we heard this recommendation?
Since this is a general advice, the most experts recommend drinking 1ml of water for each Kcal introduced with the diet. Therefore, since in a liter there are 1000 ml and since an average diet brings around 2000 Kcal, the accounts return to perfection!
What few people know is that the origin of this recommendation dates back to 1945 by the US National Research Council. This research body suggested that an adequate daily intake of water should be around one ml for each kcal of food, specifying immediately that most of this amount of water is contained in food.
Therefore drinking about two liters of water a day can be considered an exaggeration.
NB: of course it is always necessary to customize these generic recommendations based on the environmental conditions and physical activity of the subject.
