I read that letter the other day, too.
We're quite strict with Bobby as I'm convinced that most things that aren't "Dog Food" are poisonous. He likes a bit of carrot and banana and has a lick from a yoghurt pot. That will be one to watch, in case they have artificial sweetener. I know that chocolate, grapes and apple pips are highly toxic. There are loads of other things too, I don't even like having flowers in the house as some, like lilies, are toxic to both cats and dogs.
http://en.wikipedia.org/wiki/XylitolI'll have to watch out for discarded chewing gum, too, although Bobby has never taken much notice so far. He is the type of dog that will try to eat anything, though