At my local parish, we've had some good homilies of late on the Holy Eucharist. In the Gospel, Christ teaches:
 So Jesus said to them, "Truly, truly, I say to you, unless you eat the flesh of the Son of man and drink his blood, you have no life in you;
 he who eats my flesh and drinks my blood has eternal life, and I will raise him up at the last day.
 For my flesh is food indeed, and my blood is drink indeed.
 He who eats my flesh and drinks my blood abides in me, and I in him.
 As the living Father sent me, and I live because of the Father, so he who eats me will live because of me.
The disciples replied, "This is a hard saying; who can listen to it?" (John 6:60)
Christ said, "my flesh is food indeed and my blood is drink indeed." And His disciples are troubled. Remember, these are Christ's "disciples" saying this. These are those who have followed Christ and committed themselves to His teachings. But they are having trouble with it.
Also, this is the first hint that one of His Apostles doubts Him. Fulton Sheen states that this is the moment in which Judas turns on Christ.
"But there are some of you that do not believe." For Jesus knew from the first who those were that did not believe, and who it was that would betray him. (John 6:64) This is the context in which the betrayal is foretold.
After this, the Scriptures say that "many of His disciples drew back and no longer went about with Him."
Think of it. Christ lost a chunk of His disciples. They just dropped out. They went back to their normal lives. Christ didn't say, "Hey, guys. I'm just speaking metaphorically. Come back. It's symbolic language." No Christ is serious on this point. "You must eat my flesh." He lets them walk away. He turns to the Apostles and says, "Do you also wish to go away?" Christ is saying, "If you can't handle my teaching about 'eating my flesh/drinking my blood,' then now is the time to leave. I'm not watering this down. This is essential. If you can't accept it, then you're free to go."
For me, this is a compelling reason to be Catholic. No Protestant denomination teaches this biblical truth. They walk away from this one. At this point they "draw back." Even Anglicans don't teach it (except for a minority party), and the presence of women "bishops" and "priests" brings profound doubt on Sacraments which are supposed to be certain and sure signs of Christ's grace.