I did a some research on this and this is what the catholic church has said:
The Council of Florence, the 17th Ecumenical (and hence “infallible”) Council of the Roman Catholic Church, said the following:
It firmly believes, professes, and proclaims that those not living within the Catholic Church, not only pagans, but also Jews and heretics and schismatics cannot become participants in eternal life, but will depart “into everlasting fire which was prepared for the devil and his angels” [Matt. 25:41], unless before the end of life the same have been added to the flock; and that the unity of the ecclesiastical body is so strong that only to those remaining in it are the sacraments of the Church of benefit for salvation, and do fastings, almsgiving, and other functions of piety and exercises of Christian service produce eternal reward, and that no one, whatever almsgiving he has practiced, even if he has shed blood for the name of Christ, can be saved, unless he has remained in the bosom and unity of the Catholic Church. (Denzinger 714).
Tell me how the above differs from the following: "At this the Jews began to grumble about him because he said, “I am the bread that came down from heaven.” They said, "Is this not Jesus, the son of Joseph, whose father and mother we know? How can he now say, ‘I came down from heaven’? (They questioned His infallibility)
“Stop grumbling among yourselves,” Jesus answered. “No one can come to me unless the Father who sent me draws him, and I will raise him up at the last day. It is written in the Prophets: ‘They will all be taught by God.’ Everyone who listens to the Father and learns from him comes to me. No one has seen the Father except the one who is from God; only he has seen the Father. I tell you the truth, he who believes has everlasting life. I am the bread of life. Your forefathers ate the manna in the desert, yet they died. But here is the bread that comes down from heaven, which a man may eat and not die. I am the living bread that came down from heaven. If anyone eats of this bread, he will live forever. This bread is my flesh, which I will give for the life of the world.”
Then the Jews began to argue sharply among themselves, “How can this man give us his flesh to eat?” Jesus said to them, “I tell you the truth,unless you eat the flesh of the Son of Man and drink his blood, you have no life in you. Whoever eats my flesh and drinks my blood has eternal life, and I will raise him up at the last day. For my flesh is real food and my blood is real drink. Whoever eats my flesh and drinks my blood remains in me, and I in him. Just as the living Father sent me and I live because of the Father, so the one who feeds on me will live because of me. This is the bread that came down from heaven. Your forefathers ate manna and died, but he who feeds on this bread will live forever.” He said this while teaching in the synagogue in Capernaum.
On hearing it, many of his disciples said, “This is a hard teaching. Who can accept it?” Aware that his disciples were grumbling about this, Jesus said to them, “Does this offend you? What if you see the Son of Man ascend to where he was before! The Spirit gives life; the flesh counts for nothing. The words I have spoken to you are spirit and they are life. Yet there are some of you who do not believe.” For Jesus had known from the beginning which of them did not believe and who would betray him. He went on to say, “This is why I told you that no one can come to me unless the Father has enabled him.”
From this time many of his disciples turned back and no longer followed him. “You do not want to leave too, do you?” Jesus asked the Twelve. Simon Peter answered him, “Lord, to whom shall we go? You have the words of eternal life.”
This is excerpted from a Protestant bible (NIV). It seems that Luther kept John 6 for some reason, but threw the baby out with the bath water. Why would Christ teach one of the longest discourses in the NT, all about His Body and Blood? So that future generations could change it to bread and grape juice? Not!
Christ’s peace.