Water for Life - Healthy Living

Water - a vital nutrient

The human body can last weeks without food, but only days without water. The body is made up of 55–75 per cent water. Water forms the basis of blood, digestive juices, urine and perspiration and is contained in lean muscle, fat and bones.

As the body can’t store water, we need fresh supplies every day to make up for losses from lungs, skin, urine and faeces. The amount we need depends on our metabolism, the weather, the food we eat and our activity levels.

Facts about water in our bodies

• Body water is higher in men than in women and falls in both with age.
• Most mature adults lose about 2.5–3 litres of water per day. Water loss may be more in hot weather and with prolonged exercise.
• Elderly people lose about two litres per day.
• An air traveller can lose approximately 1.5 litres of water during a three-hour flight.
• Water loss needs to be replaced.
• Foods provide about one litre of fluid and the remainder must be obtained from drinks.
• Water is needed for most body functions
• Water is needed to:
• Maintain the health and integrity of every cell in the body.
• Keep the bloodstream liquid enough to flow through blood vessels.
• Help eliminate the by products of the body’s metabolism, excess electrolytes, for example sodium and potassium, and urea which is a waste product formed through the processing of dietary protein.
• Regulate body temperature through sweating.
• Keep mucous membranes moist, such as those of the lungs and mouth.
• Lubricate and cushion joints.
• Reduce the risk of cystitis by keeping the bladder clear of bacteria.
• Aid digestion and prevent constipation.
• Work as a moisturiser to improve the skin’s texture and appearance.
• Carry nutrients and oxygen to cells.
• Serve as a shock absorber inside the eyes, spinal cord and in the amniotic sac surrounding the foetus in pregnancy.

Dehydration
Dehydration occurs when the water content of the body is too low. This is easily fixed by increasing fluid intake. Symptoms of dehydration include headaches, lethargy, mood changes and slow responses, dry nasal passages, dry or cracked lips, dark-coloured urine, weakness, tiredness, confusion and hallucinations. Eventually urination stops, the kidneys fail and the body can’t remove toxic waste products. In extreme cases, this may result in death.
 
Recommended daily fluids
Approximately six to eight glasses (at least 150ml each) of a variety of fluids can be consumed each day. More than eight glasses may be needed for physically active people, children, people in hot or humid environments, and breastfeeding women (who need an extra 750–1,000ml per day). Less water may be needed for sedentary people, older people, people in a cold environment or people who eat a lot of high water content foods.