WATER

Perhaps surprisingly, water is the largest single component of the human body - the average man contains about 45 liters. It is essential to every bodily function, and without it we would die after two or three days.

To keep alive we all need a regular intake of both food and water, but of the two we need water more regularly. The body has stores of fats and carbohydrates which can be drawn on if food is short, and a person can survive for remarkably long periods without eating. But the body has no method of storing water, and without it death occurs in about three days since water is absolutely vital for all major bodily functions.

IMPORTANCE OF WATER

Water (chemically known as H20) is the simplest compound of hydrogen and oxygen, elements which are essential to living matter and to every life process.

The body is made up of approximately 70 per cent water, with certain tissues such as the grey matter in the brain containing up to 85 per cent, and other tissues - such as fat layers - only 25 per cent. It is also the base for the body's major transport system: blood is 80 per cent water and this takes food (in the form of sugars) to the tissues and, on its return. takes waste to be excreted.

Luckily, the body has the necessary machinery to tell us when we need water. Thirst is a basic human drive; when we feel thirsty, the body is signal ling its need for water. The volume of water we then drink in order to satisfy the body's needs is dependent on how much water the body has lost.

WATER LOSS

The body is continuously losing water through cooling, lubrication and excretion. Most of this loss occurs through the kidneys when we urinate. However up to 1 litre (1 3/4 pints) of water can be lost from the moist membranes of the lungs as we breathe out. This can be seen in the ‘ steaming breath' caused by water vapour condensing on a cold day. We also lose some in tears when we cry or when our eyes are irritated, in our saliva, in our faeces and mucous secretions such as a streaming nose or even mucus lost during sexual intercourse.

In addition, we lose water in our sweat, not just when we are excessively hot, but during everyday activity. In a temperate climate the average person may lose about a litre (1 3/4 pints) of water a day, while in hot climates, this can increase dramatically to as much as 8.5 litres (15 pints). Consequently, the normal intake of about five pints 'per day in temperate climates should be correspondingly increased.

Only in extremely rare cases do we find ourselves short of water as we are continually taking in the amount we need through both drink (coffee, tea. milk etc) and food. In fact, up to 90 per cent of some vegetables are water.

DEHYDRATION

If too much water is lost and not replaced, this will lead to dehydration, a condition that normally only occurs in hot climates where water is in short supply, and during illness. Severe dehydration can lead to both physical and mental changes. The physical symptoms include dry skin, weakening muscles, the loss of skin elasticity, and dark-colored urine that gradually ceases to flow.

Further complications, such as uraemia, can arise when the kidneys, by not excreting water, retain toxic waste substances and this leads to a form of blood poisoning.

Mentally, the sufferer can become disorientated and begin to hallucinate hence the popular image of lost desert travellers seeing mirages of oases.

WATER LOSS THROUGH ILLNESS

It is with illnesses such a cholera and dysentery which produce fever, vomiting and diarrhoea, that much water can be lost and ' severe dehydration result. During illness, water in the body heavily involved in ridding the body of its poisons and wastes and in cooling the body during bouts of fever. So any cold or fever needs to be accompanied by an increase of fluid intake.

Severe diarrhoea in small children and, babies can be extremely dangerous. When it leads to dehydration, the lips, tongue and mouth of the child become dry and the child is continually thirsty. The anterior fontanelle (the soft spot at the top of a baby's head where the bones of the skull have not yet fully fused) is depressed and the child may feel cold when you touch him; in its severest form, the child may begin to turn blue as the circulation begins to falter.

Intravenous fluids may need to be administered to restore the water balance, although oral prescriptions of water and salts help the situation immense. The cause of the diarrhoea and vomiting needs to be treated separately before water content in the body can be naturally restored.