Q. Two weeks ago, a 28-year old mother of three died after competing in a California radio station's contest to see how much water participants could drink before going to the bathroom. She got a bad headache and died of water intoxication — all for the prize of a Wii game system. My wife drinks eight glasses of water a day. Is this really worth doing?

A. There is no evidence that drinking extra water is good for you — that it helps you lose weight or improves health. And if you have certain heart, liver or kidney diseases, or use drugs such as water pills for high blood pressure, extra fluids or water may actually be harmful, excessively diluting your blood and causing tiredness, headaches, confusion or seizures.

In a study published in the journal Nutritional Neuroscience in 2003, drinking extra water before a hot pasta lunch did not reduce food intake, whether done immediately or 30 minutes before eating. There is no evidence that drinking extra water prevents or treats urine infections.

What about drinking extra fluids with colds, coughs, sore throats, sinus infections or the flu? The highly regarded Cochrane Database research group studied this issue recently. Using only the most accurate type of study — randomized-controlled trials — they found that although drinking extra fluids has been recommended to replace losses from fever or evaporation and perhaps thin the mucus, there is no actual scientific evidence of either benefit or harm, and there are reasons why drinking extra fluids may be harmful.

Anti-diuretic hormone is produced in extra amounts with various lung infections (bronchitis, bronchiolitis and pneumonia caused by either viruses or bacteria). But ADH blocks the kidney's ability to get rid of extra water, so drinking extra liquids when you have a bad cough may then lead to excessive dilution of your blood or even circulatory system overload. For example, in 2004, the British Medical Journal described a study on children with pneumonia in which four kids had such severe dilution of their blood that they died.

In folks who have had kidney stones, the Cochrane group found suggestive, though inconclusive, evidence that drinking extra water helps prevent future stones. And you should drink extra fluids if you have fluid losses from vomiting, diarrhea, sweating on hot-and-humid days, prolonged exercise or other causes. But in general, listen to the wisdom of your body and just drink when you're thirsty.

Dr. Landis Lum is a family-practice physician for Kaiser Permanente and an associate clinical professor at the University of Hawai'i's John A. Burns School of Medicine. Send your questions to: Prescriptions, Island Life, The Advertiser, P.O. Box 3110, Honolulu, HI 96802; islandlife@honoluluadvertiser.com; or fax 535-8170. This column is not intended to provide medical advice.