Water: The myth of eight glasses a day

We all know we’re supposed to drink eight glasses of water every day in order to keep our body hydrated.  But is this right – and, if we follow the advice, are we creating more harm than good?

The prestigious Mayo Clinic thinks we could be, and that the eight-glasses-a-day guide is based on nothing more than an urban myth conjured up in the 1990s.

Francois Lette and Jamie Dwyer at the clinic in Jacksonville in Florida point out that drinking too much water can result in a condition known as hypochloraemia, where electrolytes in our system can get dangerously low, causing fatigue, irritability and cramps.

Drinking water also dilutes our natural levels of sodium and chloride, which are also lost when we sweat – and trying to correct that too quickly by drinking a lot of water can result in brain damage. 

These days the advice has changed.  Athletes and the military are told not to drink too much fluid, and the number of water stations around a marathon run has been halved.

The Mayo’s advice?  Just go with what your body is telling you, and you won’t go too far wrong.

(Source: The Lancet, 2008; 372: 782-4).