John 6
48 I am the bread of life. 49 Your ancestors ate the manna in the wilderness, yet they died. 50 But here is the bread that comes down from heaven, which anyone may eat and not die. 51 I am the living bread that came down from heaven. Whoever eats this bread will live forever. This bread is my flesh, which I will give for the life of the world.”
In all of the new testament nobody ever left Jesus because his teaching was to difficult... until you get to the teaching about the last supper. Never in all of the new testament does Jesus EVER repeat himself except in this passage and he says the same thing over and over like 6 times. Also of note... this is the first evidence of Judas turning away from Jesus.
Jesus very clearly says my flesh is real. If you eat it you will live forever, if you don't you won't.