My husband has proposed that the reason you should not eat fae food or drink is because they are then able to harvest your DNA (i.e., your true name) from their flatware/cups. They are then able to clone you at their leisure and replace you (i.e., a changeling). The whole thing is that the fae are not magical at all. They are just extremely technologically advanced (like in Artemis Fowl).
I pointed out that this idea is low-key hilarious because the culture the fae are based on (the Tuatha De Danann) died out because they were *not* technologically advanced (they were driven out by invaders who had superior technology, i.e., iron weapons. Yes... that is why the fae are said to be weak to iron).
His response? The survivors became focused on advancing technology so that they would never again be defeated by someone else having superior technology to them.