Many people look at this passage and see the terms “bread” and “drink” and assume that Jesus is making reference to the future institution of the Lord’s Supper. In fact, those of a Catholic belief use this passage to support the idea that the Eucharist actually becomes the literal body and blood of Christ.
What does the Bible teach?
John 6 is NOT about communion. When Jesus talks about “eating His flesh”, He is tying it back to the idea of Him being “the bread of life” (John 6:35). Many in John 6 were asking Jesus to perform a physical sign such as raining down bread from heaven like the manna in the Old Testament or at least replicate the feeding of the 5000 (John 6:26,31). Jesus informs them that they should not be seeking physical bread which perishes, but a food that “endures to eternal life” (John 6:27).
When one believes in Jesus and abides in His Word, it is as if they are consuming Jesus. If you consume Jesus you will receive spiritual nourishment that results in everlasting life. Jesus’ spiritual nourishment is everlasting, He states:
“I am the bread of life; whoever comes to me shall not hunger, and whoever believes in me shall never thirst” (John 6:35). If one abides in Jesus they will never lack spiritual nourishment. One abides in Jesus by hearing and learning His teachings. “Everyone who has heard and learned from the Father comes to me” (John 6:45).Jesus makes it very clear that He is not talking about physical food at all (like the communion), but spiritual food that results in spiritual nourishment.
“Truly, truly, I say to you, he who believes has eternal life. “I am the bread of life. “Your fathers ate the manna in the wilderness, and they died. “This is the bread which comes down out of heaven, so that one may eat of it and not die. “I am the living bread that came down out of heaven; if anyone eats of this bread, he will live forever; and the bread also which I will give for the life of the world is My flesh.” (John 6:47-51).
The disciples were still confused by what Jesus was saying (possibly they were still thinking He was speaking of physical bread or even His physical body). Jesus explains to them,
“...The words that I have spoken to you are spirit and life. But there are some of you who do not believe” (John 6:63-64).Many of Jesus’ followers did not believe, and thus, they did not accept this teaching and left Him (John 6:66). Peter on the other hand understood that He was to be nourished on the words of Jesus. He knew that learning from Jesus was the same as eating “the bread of life” (ie. Jesus). That is why He makes the statement “Lord to who shall we go? You have the words of eternal life” (John 6:68).
In John 6, the phrases about eating the flesh of Jesus or "bread of life" and drinking His blood is not in reference to any physical food such as the elements of the communion. Instead, the teaching of this passage is one must be spiritually nourished on the words of Jesus in order to have eternal life.
by Cliff Sabroe (References from ESV Bible and NASU95 Bible)