Aside from allergies and special cases (lactose intolerance for instance and other problems down to genetics) there are no unhealthy foods in the sense in which

Aside from allergies and special cases (lactose intolerance for instance and other problems down to genetics) there are no unhealthy foods in the sense in which you put it. There is the question of a balanced diet whereby some foods should be eaten in very moderate amounts and with attention to one's own body chemistry.