The adult body is composed of 60-70% of water. The body must expel a minimum of about 500 ml of water each day as urine, just sufficient amount to transport waste products produced by metabolic activities of one day. Water is lost by way of vapor from the lungs and sweat from the skin; also,some excretion from feces. Water lost from the lungs and the skin is responsible for one half of daily losses, although a person is not visibly sweating.
Fluid intake is best met by water. Alcoholic beverages and those containing caffeine, such as coffee, tea, sodas can not be substituted for water. Caffeine and alcohol behave as diuretics which cause the body to excrete close to half of the liquid consumed from the beverage.
Water recommendation for adults:
1.0 - 1.5 ml / kcal expended
4.2 - 6.3 ml / kj expended
For example, a person who expends 2000 kcalories a day needs about 2 to 3 liters of water ( about 7 to 11 cups).
