"Poisoned or tainted food" is just a sensationalist term for "not FDA approved" or "not handled by a certified food professional". It's kinda over the top in this regard but remember when people put borax in their milk to make it taste better or lime and plaster into bread to stretch the flour? It was unregulated food. Just like you can't open an unregistered and unlicensed restaurant without certfied cooks, you can't just hand out foods without someone knowing (i.e. licensed) how the food is supposed to be handled.