"I am the Bread of life."  Jesus was expanding the understanding of the people of his day. Their focus was limited to physical food. Jesus tells them that physical food is necessary but not sufficient for eternity. He desired to give them food that would nourished the spiritual life that God desires them to share now and eternally.  Manna was for the day and their ancestors still died. But the one who eats the Bread of life will live forever even after they died. At the time, people didn't have much of an understanding of life after death, except as a state of nothingness. Jesus told them. "I am the living bread that came down from heaven; whoever eats this bread will live forever; and the bread that I will give is my flesh for the life of the world.” This last statement was the stumbling block for them. Because they couldn't fully accept him, they could not accept his word. We truly believe that the bread and wine are the real Body and Blood of Christ, not a symbol. If Jesus meant it to be a symbol, he would have said so.