When Jesus told His disciples to eat His flesh and drink His blood, they left Him. To them and the culture that they were in ... taught from childhood in their Jewish faith ... they didn't drink blood because the blood is where the life is. And they certainly didn't eat the flesh of anything that had died on its own. They had to kill the meat that they ate and drain the blood out before eating it.
What Jesus had said didn't make any sense to them. In fact, it went totally against their cultural learning ... the way that they were brought up. So their response to Him was: "This is a hard saying. We don't receive this. We aren't cannibals." But Jesus didn't mean it that way. They didn't understand ... they couldn't.
I think that Jesus said it for our benefit, so we can see that when we feed on His Word, we're feeding on His body. The Word is His body ... He is the Word.
Reverend Robert W. & Mary C. Butler