There's no ambiguity. We are supposed to eat the flesh of Christ and drink his blood.

  "If it's just a symbol, to hell with it"!  Said one of my favourite writers, Flannery O'Connor.  She was of course, referring to the real presence of the Eucharist.  "Take note of those who hold heterodox opinions on the grace of Jesus Christ which has come to us, and see how contrary their opinions are to the mind of God… They abstain from the Eucharist and from prayer, because they do not confess that the Eucharist is the Flesh of our Saviour Jesus Christ, Flesh which suffered for our sins and which the Father, in his goodness, raised up again. They who deny the gift of God are perishing in their disputes. —Letter to the Smyrnaeans, Ch 6.  I highly doubt that someone that was a disciple of the Apostle John would get something so seriously wrong.  What's that you say?  Some early Christians held views that would be deemed heretical?  Okay, let's go right to the Bible itself.  "Now, as they were eating, Jesus took bread, and blessed, and broke it, and gave to the disciples, and said 'Take eat; this is my body.'  And he took a chalice, and when he had given thanks, he gave it to them saying 'Drink  of it, all of you, for this is my blood of the covenant, which is poured out for many for the forgiveness of sins." (Matthew 26:26-28, this verse is paralleled verses, Mark 14:22-25, Luke 22:19-20, though Luke then goes into detail about Jesus's betrayal).  Whoa.  Blood of the covenant?  Now, what is a covenant?  A covenant is an agreement.  Usually, in biblical terms, a covenant is an agreement God makes with his people.  Take for instance, the agreement that God made with Noah (which I learned from Baptist Sunday school, and I am very thankful for)"But I will establish my covenant with you; and you shall come into the ark, your sons, your wife, and your sons' wives with you".  Genesis 6:18.  Now, of course, God tells Noah that the bow is a sign between God and the earth.  (On a different note, I remember that every time I see a rainbow).  One thing that many people do, when we Catholics are clever enough to quote John 6, pretty much the whole thing (the Eucharistic discourse).  Of course, Protestants are quick to point to 6:63.  Now are you saying that Jesus's flesh is of no avail?  That would be blasphemy.  Now, we Catholics use John 6 as a proof text, because 1) Many of his followers left him, (John 6:66)  2) If it were symbolic, Jesus would have made an attempt to explain it, he did not. And in fact, as Our Lord pointed out, "But there are some of you that do not believe".  (John 6:64).  Please think of the term Jesus uses when translated to Greek.  "Trogo".  Which means to "chew" or "gnaw".  This is a pretty graphic term.  He uses this four times in the discourse (his language shifted from the more common "esthio", the the more graphic term).  I don't know if there is a difference between those terms in Aramaic, but the fact that St. John chose to mark the change means that he knew there was a change in shift.  I don't know about you, but when it comes to the Eucharist, I'll take Jesus at his word
Prooftext used from RSV-CE.  Mainly Ignatius study Bible.