The Romans misunderstood passages like this. They accused the Christians of being cannibals. The misunderstanding came from the fact that it was literally interpreted. Jesus was teaching a spiritual truth here as noted in verse 63.
John 6:63 (KJV)
(63)”It is the spirit that quickeneth; the flesh profiteth nothing: the words that I speak unto you, they are spirit, and they are life.”
To the Jews, blood stands for life and belongs to God. They will not eat meat with blood in it. This is why they struggled with this statement. In this context, the taking blood and flesh was not literal. Jesus was speaking about taking His life into ours. Just as food becomes a part of our lives, Jesus Christ is to become a part of our lives. Food influences our health and strengthens us. Jesus does the same thing for us.
Verse 58 speaks of the second kind of manna. That which came down from Heaven is spiritual. Whoever eats this bread shall live forever. There are various interpretations concerning these verses. One of the views states that it is a memorial or testimonial. This understanding focuses on the words “Do this in remembrance of me” along with Paul’s statement “For whenever you eat this bread and drink this cup, you proclaim the Lord’s death until He comes. I Cor. 11:26. There is truth in this view.
Another view is one which John Calvin interprets these verses. Jesus is actually present in the communion service but that He is present spiritually, and not in a physical way. Calvin calls this understanding the doctrine of the “real presence.” It is taught that God is everywhere present. He is not physically present in all things. This would be pantheism. He is present spiritually. He dwells in His children. This is a special abiding. It is received by faith.
These things were spoken by Jesus in the synagogue in Capernaum. The disciples of Jesus considered this a hard saying. In other words, these words were hard to accept. They could not comprehend this with their natural minds. Jesus knew they were wondering how to handle this statement. Jesus wanted to know if what He had just taught offended them. Jesus gave them another spiritual statement, and I am sure they did not understand this statement either. What if they saw Jesus ascending where He came from? They saw this in Acts 1. I am sure they were amazed then.
Jesus goes on to tell them that He knows who will betray Him. Only those who were given to Him will come to Him. They must be drawn by the Father. (Verse 44)