Drinking water

Why drink water?

Water is an essential nutrient and makes up 50-60 % of the human body weight. The average person can survive for about 40 days without food, but most people will die if they go for more than 72 hours without a drink.

An average adult body contains 35-45 litres of water, with approximately 2 litres located within the body's cells and one-third distributed in the blood vessels and between the cells in tissues and organs. Water is necessary for all the chemical reactions that occur in our bodies. It is involved in digestion, elimination of waste, regulation of body temperature, production of saliva, and other processes.

How much water do you need?

The Australian guidelines recommend consumption of the following amounts of fluids (including plain water, milk and other drinks such as tea and coffee) per day:

  • adult men: 2.6 L/day (roughly 10 cups);
  • adult women: 2.1 L/day (roughly 8 cups);
  • pregnant women aged 14-18: 1.8 L/day;
  • pregnant women aged 19 to 50: 2.3 L/day;
  • breastfeeding women aged 14-18: 2.3 L/day;
  • breastfeeding women aged 19-50: 2.6 L/day.

Some water will also come from solid foods. Most fruits and vegetables consist of 80-90% water and even lean cooked meat is 50-60% water.

For the body to keep functioning normally and maintain adequate health, it needs a steady supply of water. Even without exercising, water losses from breathing and perspiration make up half of the turnover of water every day. With exercise, hot weather and low humidity, this loss can increase much further and requirements may be much higher than the general recommendations.

Under most circumstances, thirst is a good indicator of fluid needs.

Complications of mild ongoing dehydration

If you consistently don't drink enough water and are mildly dehydrated, you put yourself at risk of several problems:

  • Increased risk of kidney stones;
  • Urinary tract cancers;
  • Colon cancer;
  • Reduced mental performance;
  • Reduced physical performance.

The elderly need to take particular care to drink enough fluids, as dehydration can lead to constipation, mental impairment, falls and stroke. The normal thirst mechanism may also fail in some frail elderly people.

Last Reviewed: 7 August 2015


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