re: what's the one food you CANNOT eat

I don't really have anything that sticks out as "I just can't eat this", but I certainly have foods I'd not want to eat unless it means starvation.

Those include:

Potted Meat
Spam
Vienna Sausages

Now, when considering what is considered a delicacy in some foreign countries-------that's another story. I've seen Andrew Zimmern eat some disgusting shite on his show when visiting far away places that I would not get close to my mouth.