The larger context of John chapter 6 is where a literalist may go to refute the notion of transubstantiation.
v.1-15 Jesus miraculously feeds a huge crowd
v. 25-26 The crowds find him and he chastises them for coming to get their bellies filled again rather than responding to the miracle.
v.27 Don't work for perishable food but for eternal food
v.28 What work avails us of eternal food?
v.29 Belief in Jesus is the work
Starting here the crowd begins to push back, asking for a sign to prove what Jesus has just said, even though the sign was just performed and Jesus had just chastised them for ignoring it.
So they said to him, “Then what sign do you do, that we may see and believe you? What work do you perform? Our fathers ate the manna in the wilderness; as it is written, ‘He gave them bread from heaven to eat.’” - John 6:30-31
v. 32-33 Jesus then indicates that manna was a figurative type and He is the anti-type; the true bread.
Now again Jesus indicates the means by which one may partake of the true bread:
“I am the bread of life; whoever comes to me shall not hunger, and whoever believes in me shall never thirst. - John 6:35
Starting at verse 36 Jesus begins to make clear that the unbelief represented in the crowd is not due to lack of proof but is rooted in human will and the providence of God:
But I said to you that you have seen me and yet do not believe. All that the Father gives me will come to me, and whoever comes to me I will never cast out. - John 6:36-37
v. 40 Jesus emphasizes belief focused toward Himself again.
The Jews in the crowd now begin to grumble about how it is Jesus can say He comes down from heaven:
So the Jews grumbled about him, because he said, “I am the bread that came down from heaven.” They said, “Is not this Jesus, the son of Joseph, whose father and mother we know? How does he now say, ‘I have come down from heaven’?” - John 6:41-42
v. 43-45 Don't grumble. You can't come to me on your own. If you haven't learned from the Father you won't come.
v. 47 Again the only emphasis is on belief.
v. 49-51 The contrast is drawn again between the results of eating Manna and eating True Bread.
v. 52 Disputes ensue
v. 53-57 Jesus puts more focus on the aspects of his teaching that are causing strife among the unbelieving:
For my flesh is true food, and my blood is true drink. Whoever feeds on my flesh and drinks my blood abides in me, and I in him. As the living Father sent me, and I live because of the Father, so whoever feeds on me, he also will live because of me. This is the bread that came down from heaven, not like the bread the fathers ate, and died. Whoever feeds on this bread will live forever.” - John 6:55-58
Notice in the above passage that AS Jesus lives because of the Father SO whoever feeds on Jesus will live because of Him. It is unlikely that Jesus consumes the Father and more likely that Jesus is drawing spiritual sustenance from the Father as we are to draw on Jesus.
This is confirmed following verse 60 where the disciples say, “This is a hard saying; who can listen to it?”. In response Jesus declares:
It is the Spirit who gives life; the flesh is no help at all. The words that I have spoken to you are spirit and life. - John 6:63
In true parabolic fashion Jesus is addressing the root cause of unbelief and the benefits of belief. As resistance to His saying increases so Jesus makes His words more offensive and difficult for those who are already bent towards unbelief. This is the entire purpose of parabolic teaching:
This is why I speak to them in parables, because seeing they do not see, and hearing they do not hear, nor do they understand. Indeed, in their case the prophecy of Isaiah is fulfilled that says: “‘“You will indeed hear but never understand, and you will indeed see but never perceive.” For this people's heart has grown dull, and with their ears they can barely hear, and their eyes they have closed, lest they should see with their eyes and hear with their ears and understand with their heart and turn, and I would heal them.’ - Mat 13:13-15
The teaching at the beginning, prior to the mounting resistance, is the most clear. Whoever comes will not hunger and whoever believes will not thirst. It is stubborn unbelief that results in the offensive proclamation to eat flesh and drink blood.