Marathon runner drank 5 litres of water and almost died
Doesn't remember the second half of the race.
Was rushed to hospital hours later and went into a coma.
Hyponatremia is caused by drinking too much water which dilutes all the salts and minerals in the body.
Water is important - but it can kill you if you drink too much.
Nutritionist, Johanna Hignett, says most people don't drink enough water.
Everything happening in the body relies on water.
Have to drink lots of water in short period of time to get hyponatremia.
People should drink 1.5 - 2 litres of liquid a day.
Easy to monitor - your urine should be straw, or champagne, colour.