Q. Why do you avoid smoking or drinking coffee, tea or alcohol?
A. Caffeine, nicotine, alcohol—to varying degrees these are all intoxicants. That is, they all have a toxic effect on the body. Devotees of Krishna eat and drink only things that can first be offered to Him, and in the scriptures He requests pure, nutritious food and beverages.
By avoiding caffeine, nicotine, alcohol, and similar substances devotees keep their minds clear for concentrating on spiritual goals.