Don't forget the other effects of caffeine. It raises blood pressure. Hypertension is called the silent killer with good reason. I've quit caffeine 3 times now. This last time was at my doctors recommendation (slightly elevated BP).

It really helped along with not drinking all the gunk in soda. Since then, I've cut salt intake, sugar binging, and set aside 30 minutes most days to get the heart rate up. I'm no "health nut" but after breaking my sedentary habits, I do feel better than I have in a long time.