Doctrine of transubstantiation has roots in the Church Fathers

One common objection to the real, bodily presence of Christ in the Eucharist goes something like this: “How can you say the Eucharist becomes the Body and Blood of Christ when it still looks like bread and wine?...” But this objection contains a misunderstanding of the doctrine, not a refutation of it.

Catholics agree that upon Consecration the bread and wine at Mass do not visibly transform into the Body and Blood of Jesus Christ. Instead, the substance of the bread and wine become the substance of the Body and Blood of Christ while the form or accidents of the bread and wine (what we observe with our senses) remain….

Since at the Last Supper Jesus did not say of the bread, “This represents my body” or “This contains my body,” but simply, “This is my body,” the concept of transubstantiation best explains the miracle God achieves through the Eucharist. The term “transubstantiation” itself was first used in a magisterial document in 1215 when the Fourth Lateran Council described how “his body and blood are truly contained in the sacrament of the altar under the forms of bread and wine, the bread and wine having been changed in substance [emphasis added; Latin, transubstantiatio], by God’s power, into his body and blood, so that in order to achieve this mystery of unity we receive from God what he received from us.” 

This does not mean that the idea of transubstantiation was unknown before the thirteenth century. In the fourth century Gregory of Nyssa described the change in the bread and wine at Consecration as “transelementation” (Greek, metastoicheiosis), which refers to a restructuring of an object’s fundamental elements. The fact that this belief was later called transubstantiation does not refute its apostolic origins, because many doctrines are later clarified with postbiblical language. … 

Saint Ignatius of Antioch said that heretics “confess not the Eucharist to be the flesh of our Savior Jesus Christ, which suffered for our sins, and which the Father, of His goodness, raised up again.” Justin Martyr said the Eucharistic prayer at Mass changes the bread and wine so it becomes “the flesh and blood of that Jesus who was made flesh.” Origen taught that the Eucharist was a new kind of manna because “the flesh of the Word of God is ‘true food,’ just as he himself says: ‘My flesh is truly food and my blood is truly drink [Jn 6:55].’” …

Since the doctrine of transubstantiation had not yet been defined, we should not expect the Church Fathers’ description of the Eucharist to conform to this idea…. However, what we do find does not support the position of many Protestants who claim that the Eucharist is merely a symbol.