A tragic example serves as an important lesson about drinking too much water.
In January of 2007, 28-year-old Jennifer Strange participated in a contest held by KDND 107.9, a radio station in Sacramento, California. The prize was a Nintendo Wii video game system. In order to win, she would have to outlast other contestants in drinking increasingly large amounts of water without urinating. The contest went on despite a call into the station from a nurse practitioner warning about how dangerous the contest was. Strange developed abdominal bloating and later an intense headache on the way home. She died later that night.
Many would agree that such a tragedy could have easily been prevented. Aside from amusement at other people's expense, a lack of health knowledge may have also played a role. People have been told to drink plenty of water each day to avoid dehydration. Drinking more than necessary may be fine provided that excess water can be eliminated in urine. However, there is more to water balance than just dehydration.
Osmosis
Suppose there is a bowl of water divided in half by a thin membrane. Water can pass through this membrane, but not salt. If a spoonful of salt is poured into the water on one side of the membrane, that side will be salty and more concentrated while the other side would be less concentrated. The salty side has both water molecules and ions from the salt competing to pass through the membrane. Water from the salty side won't pass through the membrane as well as water from the non-salty side. In effect, water shifts from a lesser concentrated solution to a more concentrated solution. The special term for this movement of water is osmosis.
When water is absorbed into the bloodstream from the digestive tract, electrolytes in the blood are diluted, especially sodium (hyponatremia). In comparison, cells in the body would be more concentrated and not as dilute. By osmosis, water moves from the bloodstream into the cells. When one is dehydrated, this shift will correct any water deficit. If one attempts to drink water when he or she is well hydrated, water will still shift in this direction for the same reason, but it can lead to cellular swelling, dysfunction, and even bursting if left unchecked. Fortunately, kidneys filter out excess water that is eliminate by urinating.
Overhydration and Dehydration
Suppose one were to forcefully drink large quantities of water in a relatively short amount of time, like two or three gallons of water over a few hours. The kidneys would not be able to filter out so much water quickly enough to prevent cellular swelling. This would especially affect the brain inside the cranium. It would not have enough time to adapt to this rapid change. When the brain swells, it gets compressed by the skull because there is no room to expand. Symptoms like headache, lightheadedness, nausea, and vomiting can occur, but as it worsens, it can lead to seizure, coma, and death. The case of Jennifer Strange is a sad illustration of this.
That is not to say that one should avoid drinking water. It is still important to stay hydrated on a regular basis because dehydration occurs much more often than water intoxication. The idea is to drink when feeling thirsty or if it has been a while since the last sip. If the urine is darker colored instead of lighter colored or colorless, it may be time to drink more water. Otherwise, drinking would feel like a struggle against the body.
Circumstances where people lose more water than usual and especially need to hydrate oneself include hot weather, exercise, diarrhea, vomiting, and illness. With vigorous exercise, hydration should involve sports drinks that contain not only water but also electrolytes. Water is lost with sweating, and over longer periods, electrolytes are also lost. Drinking large amounts of water under these circumstances would quickly dilute the blood, leading to significant osmosis into the cells.
Final Words
Water is a necessary substance for life, but even overhydration can be fatal. One should drink regularly and when needed. One should not drink too much too quickly, especially if under peer pressure as in a water-drinking contest. Otherwise, a precious life could be lost needlessly.
