Any health journal or magazine you read you’ll find is always telling you to dink, drink, drink (water that is… not alcohol of course) and this is especially true if you’re walking through a desert or running a marathon. However what’s important to note is that it is possible to drink too much and if you do so you can end up causing more damage than if you weren’t drinking at all. This is what is known as ‘water intoxication’ and it’s very important that we avoid this.
Water intoxication, sometimes also called water poisoning or hyponatremia, occurs when we drink too much water in too short a period of time. The problem here is caused by the fact that we end up reducing the balance of electrolytes in our body by literally ‘watering them down’ and this then prevents our brain from being able to send the necessary electrical signals.
During exercise or exposure to heat this is particularly dangerous – not only because individual will then attempt to hydrate themselves more than usual, but also because they will tend to sweat more which means they lose a lot of sodium (salt) which is one of the body’s main electrolytes. Another risk factor is low body mass – the smaller and lighter you are, the more likely you are to ‘overdose’ on water.
The best prevention is simply to ensure that the intake of water does not largely exceed the amount lost. When running a marathon or otherwise engaging in endurance challenges, the aim is to replace the water that you are losing – and not to try to add more water. The same goes for trekking in the heat, and in either situation you need to avoid drinking too much anyway to ensure that you don’t make yourself feel sick (for running) or run out of water.
Instead make sure to take only very small sips (which takes a lot of self control granted) or to try just holding the water in your mouth which will help your body to hydrate itself by absorbing the moisture through the roof of your mouth and under your tongue.
You should also make sure to replace the salt that your body loses which you can do by enjoying one or two salty snacks, or more effectively using an ‘isotonic’ sports drink, which is designed to contain sugar, water and salt in the same ratios as your blood to help replenish you accordingly.
Treatment will normally consist of fluid restriction, and in more severe cases diuretics (to encourage urination) and vasopressin receptor agonists.