Water

The body is made up of about 70 per cent water.Water is vital in most of the processes that are integral to health. Even mild dehydration (e.g. losing about 70ml of fluid for a 70kg adult) can impair essential body

processes and cause symptoms such as headaches, appetite loss, fatigue, muscle

weakness, light-headedness and dry eyes and dry mouth.

Keeping well hydrated also seems to help reduce the risk of chronic disease. Research indicates, for

instance, that low levels of fluid consumption are associated with increased risk of cancers of the kidney,

bladder, prostate and testes. Other research has found that increasing fluid intake seems to reduce the risk of bladder and colon cancer. Evidence also suggests that drinking water may reduce the risk of heart disease. In one study, women drinking five or more glasses of fluid each day had a 41 per cent reduced risk of dying from a heart attack compared to women drinking two or fewer glasses each day, and for men the risk was reduced by 54 per cent.

As a rough guide, drink about 30ml of water for each kilogram of body weight. For most people, this equates to 1.5–2.5 litres of water a day. However, individual needs can vary with factors such as outside temperature and activity. A good guide to our state of hydration is the colour of the urine. The aim is to drink enough water to keep the urine pale or very pale yellow during the day. The quality of the drinking water is important, too. Tap water contains chlorine. This can induce chemical changes which, at least in theory, should increase cancer risk. It seems sensible to drink filtered tap water or mineral water.