A new study to be published in a forthcoming issue of the Journal of the Royal Society of Medicine says that marathon runners should limit the amount of water that they drink during the race or they may be faced with complications like headache, collapse, confusion, memory loss, vomiting, seizures, and even death from fluid accumulation in the lungs or brain.
All these complications result from an excess intake of water during exercise (exercise-associated hyponatraemia or water intoxication). "One patient in the study estimated that he drank approximately 13 liters during the five hours he took to complete the marathon which is more than five times the recommended amount. Drinking excessively before, during and after the event can be extremely dangerous," said Dr Dan Tunstall-Pedoe, co-author of the study and Medical Director of the London Marathon. Guidance published on the London Marathon website ask runners to not drink more than half a litre of water per hour in cool weather. For those who take less than 3 hours 30 minutes to complete the race a liter per hour may be needed. The study examined fourteen runners from the 2003 London Marathon who were treated at St Thomas' Hospital for EAH. It was also noted that women were at a higher risk for developing the condition. All patients were treated with 1.8% hypertonic saline and recovery was generally quick. "Not only did they suffer some extremely unpleasant symptoms," Dr Tunstall-Pedoe concluded, "but most of the patients in our study had confused memories of running the marathon and many did not remember the elation of finishing. We are encouraging this year's participants to drink safely and leave the event with some great memories of their achievements."