actually Vit D drops ARE good to give when BFing IF the baby is not getting regular sunshine, HOWEVER get a brand that ONLY has Vit D (D3 to be exact) where you only have to give ONE SINGLE DROP per day. Anything that requires more than that, has stuff in it that is not needed.
lots of good info here:
I am a very strong advocate for BFing, EBFing, BFing past 2 yrs and not supplementing whenever possible. Vit D drops are the ONLY supplements I ever gave my kids.