Review the word "Spirit" in scripture.
The word spirit comes from the Latin word spiritus, or breath. In Greek it is pneuma from which we get pneumonia and pneumantic. In Hebrew it is ruah.
**In the beginning God created the heavens and the earth. The earth was without form and void, and darkness was upon the face of the deep; and the Spirit of God was moving over the face of the waters.* (Genesis 1:1-2 RSV)*
Other translations say that a "Mighty wind" swept over the face of the deep. This is the creating, life giving spirit of God, the breath of God which creates, and gives life. The Latin, Greek and Hebrew words spiritus, pneuma and ruah, all convey the sense of breathing or of moving air.
**then the LORD God formed the man out of the dust of the ground and blew into his nostrils the breath of life, and the man became a living being. (Genesis 2:7)
Again we see God breathing. God's spiritus is a life giving force. God's ruah/spiritus/pneuma/breath/spirit is what makes man a living being.
**He asked me: Son of man, can these bones come to life? "Lord GOD," I answered, "you alone know that." Then he said to me: Prophesy over these bones, and say to them: Dry bones, hear the word of the LORD! Thus says the Lord GOD to these bones: See! I will bring spirit into you, that you may come to life. I will put sinews upon you, make flesh grow over you, cover you with skin, and put spirit in you so that you may come to life and know that I am the LORD. ... Then he said to me: Prophesy to the spirit, prophesy, son of man, and say to the spirit: Thus says the Lord GOD: From the four winds come, O spirit, and breathe into these slain that they may come to life. I prophesied as he told me, and the spirit came into them; they came alive and stood upright, a vast army. (Ezekiel 37:3-6,9-10)
Here again, God's life giving spirit is seen as moving air. God's ruah brings the dry bones to life. Jesus speaks of being born in the context of moving air and the life giving pheuma of God in his conversation with Nicodemus about baptism.
**What is born of flesh is flesh and what is born of spirit is spirit. Do not be amazed that I told you, ‘You must be born from above.’ The wind blows where it wills, and you can hear the sound it makes, but you do not know where it comes from or where it goes; so it is with everyone who is born of the Spirit.” (John 3:7-8)
Jesus then goes on to breathe on the twelve.
**And when he had said this, he breathed on them **and said to them, “Receive the holy Spirit. Whose sins you forgive are forgiven them, and whose sins you retain are retained.” (John 20:22:23)
Jesus' breath is the mechanism whereby they are given the special gift of the Holy Spirit which allows them to forgive sins and bring people back to spritual life. The image of moving air as a life giving force, the breath of God which creates and gives life, is the context in which we have to understand Jesus' words in John 6:63-64.
**It is the spirit that gives life, while the flesh is of no avail. The words I have spoken to you are spirit and life. *(John 6:63)*
It is the life giving breath of God, his creative ruah, which gives life. That's the same life giving and life sustaining breath which blew over the waters in Genesis 1, which was blown into man's nostrils to make him a living being in Genesis 2, which blew on the dry bones and brought them to life in Ezekiel 37, and which blew on the Apostles in the upper room, giving them the ability to restore sinners to life in John 20.
The flesh is of no avail.
Your eyes will see bread. Your nose will smell alcohol. Your tounge will taste wine. Your human mind cannot now possibly understand what I am going to fully reveal to you on the night before I am to die, nor human reason and intellect ever fully comprehend it.
The words I have spoken to you are spirit... and life!
The Eucharist will be your life, the breath of God within you. It's about spiritus, pnuema and the ruah of God breathing life into you, and food which gives life.