The amount of water present within the body varies considerably from one living being to another. In the case of mammals, factors that influence most on the amount of water in the body are:

-    Age: less amount of water as one ages.
-    Weight: water amount decreases with increased weight.
-    Sex: more water in men than women.

In general, the daily intake of water for a healthy adult who does moderate physical activity, in a normal climate, ranges from 2.5 litres to 3 litres. Since between 50 and 70% of this daily amount is obtained from food sources, under normal conditions we need to drink about 1.5 litres of water.

We can get dehydrated if these water requirements are unsatisfied. Dehydration means a reduction of water within the body, and effects can vary depending on amount of liquid lost. Tests carried out show that a water loss corresponding to 10% of body weight can produce serious health problems and may lead to death when such loss reaches between 20-25% of body weight. Death due to lack of water may occur over a period of 10-14 days in temperate climates and over a period of between 36 and 72 hours in desert environments.

Daily water needs

Babies: Upon birth: 150 ml of water/kg of body weight.
A year later: 100 ml of water/ kg of body weight.
Children: From 1 to 1.5 litres according to age
Adults: 1.5 litres
Senior citizens: 1.5 litres