Water

It is an astonishing fact that the human body is basically two-thirds water. Without it most people are dead in four days. In normal circumstances in twenty-four hours we lose 1.5 litre of water in urine, 750ml through the skin, 400ml in the breath, and 150ml in faeces. Thats a total of 2.8 litres a day. A simple equation would suggest that this is what you need to drink.

Water has many roles throughout the body other than flushing the kidneys, including dissolving minerals, and acting as a delivery system, a lubricant and temperature regulator.
Even very mild dehydration can lead to constipation, headaches, lethargy and mental confusion, while increasing the risk of urinary tract infections and kidney stones. When just 1 per cent of body fluids is lost, body temperature goes up and concentration becomes more difficult.
The thirst mechanism kicks in when we've lost between 1 and 2 per cent of body water. However, the thirst reflex is often mistaken for hunger. If we ignore it or mistake it for hunger, dehydration can continue to around 3 per cent, where it seriously affects both mental and physical performance. Sports nutritionists have found that a 3 per cent loss of body water results in an 8 per cent loss in muscle strength.