A Simple Post about Transubstantiation

With all the news about the new Pope, I’ve been thinking about the doctrinal differences between Catholics and Protestants. I do not come from a Catholic background, but one thing I’ve never understood is the doctrine of transubstantiation.

First, other than Catholic tradition or dogma, what reason is there to think the doctrine is actually true?

Second, since Catholics do believe it is true, why don’t they also consider themselves to be practicing cannibalism–the eating of the flesh of another person–every time they eat the flesh and drink the blood of Christ? And, even if they have some way to get around the label of cannibalism, from a purely subjective point of view, this doctrine is literally disgusting to me. If I were a Catholic and believed transubstantiation, every time I took the Eucharist I would be grossed out.