Please forgive my forewardness here, but I won't mince words about this with you. The pesticides used on coffee and cocoa plants are deadly to everything. If you do not drink organic coffee you are drinking little more than poison.
Coffee, tea, and chocolate are very, very nutritious foods. The fact that your body desires them, and the caffine, is a akin to eating protein because that is what your body needs at the time.
Aside, purchase "fairtrade" organic products, knowing your luxury is not produced from slave labor. I have included some links, and while not from medical papers (can't find the proper links now) they confirm what I say.