In order for caffeine to pass into breastmilk, you'd have to consume 500 mg. That's ten cokes, five cups of coffee, and three energy drinks. I don't even think I could drink that much if I tried! Contrary to popular belief, your breastmilk does not magically contain everything you eat. It is made from your blood using only what your baby needs. Nothing more. Nothing less. Only the proteins of what you consume pass into your breastmilk and have a chance of affecting baby (like lactose). Even then, however, only certain babies are senstive to certain proteins. Chemicals like caffeine and alcohol only pass into breastmilk when you consume some much that it satutates your blood, and even then you'd probably be dead before it started to seriously affect your baby. (Yes you heard me right; you can drink alcohol and breastfeed because by the time you drank enough for it to pass into your breastmilk, you'd be dead of alcohol posioning.) Smoking, of course, will only affect baby like second-hand smoke would. It doesn't pass into your breastmilk or anything.