w: That explains the explosion in water retension
Caffeine is a diuretic, so coffee newbies pee out the water quickly; java junkies build up resistance.
Diuretics are sometimes prescribed for people with water retention problems, sometimes associated with circulation (heart) problems. My father was. And my father was a life-long coffee drinker. As in, according to this analysis from Wired.com, a diuretic-resistant person, due to a caffeine habit.
Check out the article, read about coffee contains compounds that fight cavities and free-radical damage (antioxidants), provide niacin when hot enough (160 degrees Fahrenheit), and also provide tastes, smells and ptomaine poison components.