COFFEE alkaline? Confused about many foods!

I am highly confused about what foods are acid or alkaline forming. One example: I was always certain that coffee was acid forming, however, then I read in many different sources that coffee (especially with caffeine in it) is actually alkaline forming (it's the caffeine I think that's supposed to be alkaline, once you decaffeinate it, it often turns into acid).

Also, olive oil is usually listed as acid forming, but also as alkaline sometimes, as well as raw milk - sometimes it's acid, sometimes alkaline.

Does anyone know for sure? Why can't they agree on what's acid or alkaline forming?? Tweet