Hyponatremia: What is It?

Yes, this includes water. Though it may be the soup of life, water can actually be toxic if ingested in excessive amounts. When this occurs it is usually based on bad or incomplete advice. Inexperienced runners, including charity race participants, often function under the outdated notion that you can't get too much water. Many participants are not competitive athletes and their pace/level of effort is not extreme; water losses are not that great. Still, in their mind is the knowledge that endurance athletes need to keep up on fluid intake during events. Hyponatremia occurs when blood sodium concentration falls to an abnormally low level prompting a rapid swelling of the brain that can result in seizures, coma and death. The key risk factor is excessive drinking—especially non-electrolyte fluids such as many types of water.

First reported in 1985, this disorder was considered be a rare phenomenon but has become more common since the early 1990s. A post-race study done after the 2002 Boston Marathon found that 13 percent of the participants experienced hyponatremia and point six percent had critical hyponatremia, a potentially deadly issue. Basically these people had gained weight from excess water consumption going into the start of the event and continued to gain as they drank during the race, partially because their relatively long race times gave them enough time to ingest more fluids than they lost.

The risk of hyponatremia can be reduced by making certain that fluid intake does not exceed sweat loss and by ingesting sodium-containing beverages or foods to help replace the sodium lost in sweat.

For most athletes, dehydration is still the primary obstacle to optimizing performance, not hyponatremia. But the message regarding this increasing problem is for the zealous, less experienced exercisers or competitors: Make sure you start off with the accurate hydration recommendations.