Among Native American traditions, it seems to go either way in the stories I have read and heard. We have stories of spirits taking care of people who become lost by feeding them and teaching them. But we also have trickster spirits that one should not trust.
In any case, I was taught that the spirit offerings left out for the spirits are for them only, as the spirit part of the food or clothing, etc. is taken. However, if one is desperate and it is truly an emergency, it is permitted by the spirits that one can eat or clothe oneself with such offerings. People who have done this though (eaten of the human' offerings to the Others), note that the food is oddly flavorless and unsatisfying. Probably because the Others have taken the spirit part, where the real flavor and energy is.
This always reminds me a little of Stephen King's "The Langoliers" where the food and matches and gasoline loose their essence, are flavorless and do not burn, once the moment in which they are part of "the active world" is gone.