Water intake

Without water, life simply isn't possible. Just consider the fact that your body is made up of 55 - 75% water - a large amount of fluid that needs to be replaced constantly. If you're not drinking enough water, you're in trouble.

More important than you may think

Apart from providing hydration, water performs many functions in the body:

• It helps to regulate the temperature of the body through respiration and perspiration - a process that's controlled by the central nervous system.
• Water also assists with the waste-filtration process of the body. Our kidneys remove waste products such as urea and lactic acid, which must be dissolved in water. When there isn't enough water, these waste products aren't removed effectively and may cause damage to the kidneys.
• We also need water to breathe. In order to take in oxygen and eliminate carbon dioxide, our lungs must be moistened by water.

How much do you need?
Adults lose about 1.2 - 1.5 litres of fluid per day through urination and about 1 litre through perspiration. Varying amounts of fluid are also lost through excretion and breathing.

To prevent dehydration, we all need approximately 2 - 2.5 litres of fluid per day. And if you suffer from diarrhoea or vomiting, your fluid needs will be even higher.

Although good, clean water is the best beverage out there, you can also ensure an adequate fluid intake throughout the day by drinking tea, coffee, juice or (preferably unsweetened) cool drink - as long as it adds up to 2 - 2.5 litres of fluid. (Just go easy on caffeinated coffee or tea, as caffeine can actually withdraw some fluid out of your body.)

Dehydration: who is at risk?

Young children and older people are at greater risk of dehydration.

Children's bodies are made up of a greater percentage of water, their metabolic rates are higher and they're at increased risk of being infected with diseases that cause vomiting and diarrhoea. They're also often dependent on others to feed them and give them fluids.

Older people may have a decreased thirst sensation, their kidneys may not work as efficiently or they may have a condition such as Alzheimer's disease, which can make it difficult for them to convey their needs to a caregiver. Incontinence may also prompt an elderly person to limit his or her water intake.

Sports enthusiasts, who partake in strenuous sporting activities, are also at risk of dehydration.

Athletes need to drink more

Vigorous exercise may lead to a water loss of 2-3 litres per hour. This puts athletes at risk of getting heat stroke or severe muscle cramps.

Research shows that most people who participate in sports don't drink enough water. In fact, most athletes tend to replace only two-thirds of the water they've lost. But proper pre-event hydration and post-event re-hydration are of fundamental importance.

One simple method in which athletes can assess the amount of water they've lost during vigorous exercise is to weigh themselves before and after exercise, and to recoup the water loss.

A note of caution though: doctors at major marathons around the world are hospitalising more and more athletes as a result of "over-drinking". Some deaths from hyponatraemia, commonly known as "water intoxication", have also occurred. This condition is characterised by too much water in the blood and too low levels of sodium (less than 130mmol/L). This points to the fact that athletes need to control their fluid intake carefully.