The good thing about sugar alcohols is that they are not digested at all, they just pass through, and they're too big to pass through the small intestine into the blood stream (is this true?)
but if proteins can pass through, i dont see how a 5 carbon sugar alcohol cant. but if they're not digested, then that's a lot of calories saved.
I've always avoided aspartame though, it might be sweet but it also has a very very weird aftertaste.