It’s common knowledge that the human body is comprised of 65% water. It’s everywhere – in the blood, the tissues and the organs. The rate at which it dehydrates depends largely on the ambient temperature and humidity.
Under mild conditions a fairly healthy individual can go around a week without water. But if people are subjected to high temperatures, it’s impossible for the human body to survive more than a few days.
How much water should we drink?
The human body generally loses around 1,5 litres through urination daily, and another litre through sweating. It’s important to drink about 2,5 litres of fluid each day to replace it. Obviously more fluid will be lost in a hot or humid environment, or in conditions of physical exertion.
Dehydration affects the kidneys, which regulate the fluid levels in the body. With increasing dehydration, the blood becomes thicker, which causes the kidneys to retain water and concentrate the urine they do produce.
When kidneys fail
This causes the blood pressure to fall, resulting in less blood passing through the kidneys. As a result, yet more water is retained and urine becomes even more concentrated. Eventually, no urine is produced at all.
Once this happens the person is in danger of kidney failure. As dehydration increases, so does thirst, and fatigue. Eventually, when the kidneys have stopped producing urine, the person may become confused and even lapse into a coma as the kidneys start to fail.
Without water, the body gradually dehydrates because water intake no longer replaces water lost through sweating, breathing, passing urine and absorption in the gut.
When the body loses water it also loses salts, including sodium and calcium, which should be replaced. In what’s been described as the greatest medical breakthrough of the last century it was found that a simple electrolyte solution of half a teaspoon of table salt, two teaspoons of sugar and a pinch of bicarbonate of soda in 150ml of boiled water could help arrest dehydration due to gastroenteritis.