If logic serves, what you have claimed is contrary to what Jesus says in v.63 “It is the spirit that quickeneth; the flesh profits nothing: the words that I speak unto you, they are spirit and they are life” .
Enjoy the Lord today
Out of context, it seems logical to interpret that line as you do. But, it’s impossible to ignore what Jesus says before that.
“[56]** For my flesh is meat indeed: and my blood is drink indeed. [57] He that eateth my flesh, and drinketh my blood,
abideth in me, and I in him. [58]
As the living Father hath sent me, and I live by the Father; so he that eateth me, the same also shall live by me**.”
Jesus is very clear about the real spiritual benefits of eating His Flesh and drinking His Blood, which is to share in His life, in the same way that He shared in the life of His Father, even while He was living as one of us, on earth.
“[59] This is the bread that came down from heaven. Not as your fathers did eat manna, and are dead. He that eateth this bread, shall live for ever.”
This is where He explains the difference between Him being the Bread of Life that gives eternal life to our souls, and the manna that the Israelites ate in the desert, that only fed their bodies.
“[60] These things he said, teaching in the synagogue, in Capharnaum. [61] Many therefore of his disciples, hearing it, said: This saying is hard, and who can hear it? [62] But Jesus, knowing in himself, that his disciples murmured at this, said to them: Doth this scandalize you? [63] If then you shall see the Son of man ascend up where he was before?”
Jesus knew that what He said would be misunderstood by all who heard it. But, at this point, He was also testing the faithfulness of His disciples. Those who truly believed in Him were the ones, like Peter, who knew that whatever He said must be the truth. They also knew that He would reveal more about what it meant when the time was right to do so, which He did at the Last Supper.
“[64] It is the spirit that quickeneth: the flesh profiteth nothing. The words that I have spoken to you, are spirit and life.”
Then, He goes on to add a bit more explanation in the line that you mentioned. He says that eating His Flesh and drinking His Blood is intended to ‘quicken’ our spirit. It is not intended to ‘nourish’ our bodies, like the manna did for the Israelites. So, “the flesh profiteth nothing” refers to our flesh, not His. It is not meant to be food for our bodies, but real food for our souls. Through the Eucharist we are joined with Him, both physically and spiritually, but it is a means of attaining eternal life with Him, not for us to live forever on earth. That’s what I believe He meant by saying “the flesh profiteth nothing”.
“[65] But there are some of you that believe not. For Jesus knew from the beginning, who they were that did not believe, and who he was, that would betray him.”
Jesus knew that it wasn’t only those that heard Him speak that would not believe that they had to eat His flesh and drink His blood to have eternal life, but as we see in this thread, there are still many people that say, “This saying is hard, and who can hear it?”.