Water consumption guidelines an urban myth
An article published online today at the American Journal of Physiology challenges the widespread advice to drink at least 8 eight-ounce glasses of water per day.
This advice seems to be recommended by just about everybody from doctors and nutritionists to health writers. However, there seems to be no evidence for it, claims Heinz Valtin of Dartmouth Medical School.
We have seen in other recent studies that water contained in drinks such as coffee, tea or caffeinated soft drinks should count toward your total water intake, even though many people seem to think it doesn't.
So could there be any harm in drinking too much water? Yes, there could. Although there are not likely to be too many problems, some disadvantages of high water intake are possible. These include increased exposure to pollutants, frequent inconvenient urination, expense (for the water snobs out there!) and guilt (from not satisfying the day's water "requirements").
There have also been cases where the kidneys can't excrete enough water, leading to "water intoxication". One of the apparent risks of the drug ecstacy is that users often drink lots of water due to associated activities (such as raves) and this can lead to water intoxication, which has been fatal on occasion.
Valtin also shatters some other urban myths of water consumption.
1) Thirst is too late. The myth claims that if you are thirsty, you are already dehydrated. However, the body's thirst response actually kicks in well before dehydration.
2) Dark urine means dehydration. In most cases, dark urine does not mean dehydration and for normal volumes of urine, there would appear to not be much chance of dehydration, regardless of color.
Of course, there are some caveats with the study... Increased water consumption is recommended in some circumstances such as during strenuous physical activity, hot weather or long plane flights. But most people would typically drink more in these circumstances anyway...
So it looks like you can put down that glass of water and face up to the fact that your regular trips to the water cooler are for social purposes rather than trying to satisfy some water consumption goal...
[David Harris' Science News]
