According to Wikipedia, "water poisoning," also referred to as water intoxication or hyperhydration, entails "a potentially fatal disturbance in brain function that results when the normal balance of electrolytes in the body is pushed outside of safe limits by a very rapid intake of water."
Ideally, excess moisture leaves the body in significant amounts when we sweat or urinate, or more gradually as we exhale carbon dioxide and small amounts of moisture into the atmosphere. Yet when water is consumed more quickly than it can be removed, a potentially fatal electrolyte imbalance within the body’s fluids results. This imbalance is due primarily to the dilution of sodium compounds (a particular kind of electrolyte), which must be kept within a very small window of concentration.
Hyponatremia, the most common cause of water intoxication, results when this overdilution of sodium occurs within the blood plasma, causing an osmotic-type reaction in which the water outside of the cell filters into the cell. The cell will then swell and likely shut down. When hyponatremia occurs within the cells of the central nervous system and brain, it causes water intoxication. Thus, it would seem that water poisoning is every bit as possible as alcohol poisoning; but does it ever actually happen?
As unlikely as it sounds, less than one week ago, CNN reported that twenty-eight year old Jennifer Strange of Sacramento, California was found dead after participating in KDND radio station’s "Hold Your Wee for a Wii" contest. The contestants, competing for a Nintendo Wii, were to drink vast quantities of water without urinating. The contestants were reportedly told not to continue if they felt their health to be at risk.
This truly bizarre occurrence comes on the heels of another death by water intoxication that took place in February of 2005 at California State University in Chico. As part of a Chi Tau fraternity hazing, twenty-one year old Matthew Carrington was to drink large amounts of water while completing various physical tasks when he collapsed and died due to water intoxication.
But, before all of us hypochondriacs go freaking out and boycotting Evian, let us note that while dehydration is fairly common, hyperhydration is incredibly rare; hydration, then, is more important than fretting over hyperhydration.
Water intoxication occurs more frequently in infants, presumably because of their relatively small stature, and in those who both sweat excessively and consume large amounts of water, such as long-distance runners or workers functioning in extreme heat and humidity. Obviously, to avoid water intoxication, you want to keep your body’s intake of electrolytes and water at pace with your losses. Avoiding inane contests, or any contest, really, that contains the phrase "Hold Your Wee," is advised.