AFAICS, the idea that caffeinated beverages actually dehydrate you is an urban legend. Like all urban legends, there is a bit of truth: caffeine does act as a diuretic. However, caffeinated beverages also contain water. The net effect is that caffeinated beverages hydrate you, but not as much as an equivalent volume of non-caffeinated beverages would. See also Eight Glasses at snopes.com.
- niraD 01:55, 26 September 2008 (EDT)