It's common wisdom that you should drink eight glasses of water a day to be healthy. But new evidence out of Britain suggests that water isn't as good for you as you might think.
Britain's Daily Mail newspaper reports that experts are begining to rethink the traditional stance on water as a health tonic. Currently, Britain's National Health Service says people should aim to drink two and a half pints, or eight glasses, of water every day.
Among its health benefits: it helps promote weight loss by inhibiting the appetite and kick-starting the metabolism; it prevents kidney and bladder infections by flushing out bacteria when you urinate more frequently; it moisturizes skin; it builds healthy nails; and it prevents dehydration.
One study, however, says dehydration is a myth, and that there's no evidence backing up the idea that drinking water can have the health benefits described above.
The Daily Mail quoted Dr. Margaret McCartney, a general practitioner who works in Glasgow, as saying the eight-glasses-of-water prescription is "not only nonsense, but thoroughly debunked nonsense," and that bottled water companies promote the health benefits of water as a way to boost business.
Previously, health experts held that being hydrated can increase your ability to concentrate. In her article in the British Medical Journal, Dr. McCartney says drinking when you're not thirsty can actually lower your concentration.
There are other negative health effects of water. Bottled water often contains disinfectant chemicals that can be bad for you. Drinking too much water can damage the kidneys, and it can sometimes even lead to hyponatremia, a condition in which the electrolytes in the body become imbalanced and the brain swells.
It's also not certain that water really helps you lose weight: Stanley Goldfarb, who's also quoted in the British Medical Journal article, says it's obviously better to drink water than soda, but that there's no evidence that drinking water before meals will suppress the appetite.