From this article, More coffee = less cancer? :
Regular coffee drinkers — defined as four cups or more a day — reduce their risk of the cancers by 39 percent, according to a study published Tuesday by the American Association for Cancer Research.
Men who drank six cups or more a day had a 60 percent lower risk of aggressive prostate cancer than men who didn’t drink any coffee.
Those who drank five or more cups of coffee a day had a reduced risk of brain tumors known as gliomas.
Past blog entries on coffee and caffeine:
Coffee Refill? It's Okay
Drinking coffee reduces risk of Alzheimer's: study
Green tea fights Alzheimer's disease