You may remember from Study Session 1 that a 50 kg adult contains about 31 litres of water and a one year old, 10 kg child contains nearly 8 litres of water. Almost every part of the body contains large amounts of water.

People can live without solid food for a few weeks, but we cannot live without water for more than a few days. An adult needs about 2–3 litres of water each day. That is why giving drinks are so important when people lose a lot of water, such as when they have diarrhoea.

Water is essential for life. We need water for a number of reasons:

• For the body to make cells and fluids such as tears, digestive juices and breastmilk
• For the body to make sweat for cooling itself
• For essential body processes — most take place in water
• For keeping the lining of the mouth, intestine, eyelids and lungs wet and healthy
• For the production of urine, which carries waste from the body.