Water is an essential part of a healthy balanced diet. Over half of the human body is made up of water. We need water to: digest food and to absorb nutrients move our bodies well get rid of waste products keep our body at the right temperature Drinking water also keeps your teeth and mouth healthy. In most parts of Australia, the tap water contains fluoride. This helps to protect against tooth decay. Water is also needed for the body to make saliva. You need saliva to wash food away from your teeth. Saliva also helps you: chew taste swallow