I bet you have always thought that there is nothing wrong in drinking a lot of water while running. After all, your aim is to stay sufficiently rehydrated for your run.

Ever thought that water could become your biggest enemy while running a marathon and that in large quantities, it can be poisonous to humans.

This phenomenon is known as Hyponatremia. Broken down, the word litarally means lack of (Hypo in Greek) sodium (Natrium in Latin). It is an imbalance of the salts (electrolytes) in the body.

There are various reasons that cause hyponatremia but only 1 that relates to runners - excessive consumption of water. Exess water dilutes the salt content in the body and results in very low concentration of sodium. This can become poisonous to the body. Symtoms can range from nausia, headaches and vomiting to convulsions, delirious behavour and confusion.

Statistics show that long distance runners are especially prone to being victims of hyponatremia. While running long distances we worry about getting dehydrated and therefore consume excessive amounts of water. In the recent Boston marathon it was found that 12% of the runners were suffering from Hyponatremia. These people had also gained a substantial amount of weight because of too much water.

Even some experienced runners have fallen prey to the misconception that drinking a lot of water is good while running. Cynthia Lucero died on the 20 mile of the Boston Marathon in 2002 and David Rogers died just after completing the London Marathon in 2007.

So before you pick up that next glass of water at the 35km mark, ask yourself if your body really needs it.