Since I've been a little kid I've heard it preached as gospel that coffee is bad for you -- or at least doesn't help you in any way other than making you jittery. After his heart attack, my great-grandfather seemed more upset that the doctors told him no more coffee than he'd been about the heart attack itself. But I could never understand what, exactly, about it is bad for you. How can something with no calories raise blood pressure and cause a whole host of other problems?Turns out it doesn't.