**CCC **
1413 By the consecration the transubstantiation of the bread and wine into the Body and Blood of Christ is brought about. Under the consecrated species of bread and wine Christ himself, living and glorious, is present in a true, real, and substantial manner: his Body and his Blood, with his soul and his divinity (cf. Council of Trent: DS 1640; 1651).
1376 The Council of Trent summarizes the Catholic faith by declaring: “Because Christ our Redeemer said that it was truly his body that he was offering under the species of bread, it has always been the conviction of the Church of God, and this holy Council now declares again, that by the consecration of the bread and wine there takes place a change of the whole substance of the bread into the substance of the body of Christ our Lord and of the whole substance of the wine into the substance of his blood. This change the holy Catholic Church has fittingly and properly called transubstantiation.”
This is a hard teaching for many today, then again it was at the time Christ said it aswell.
**John 6:56 For my flesh is meat indeed: and my blood is drink indeed. 57 He that eateth my flesh, and drinketh my blood, abideth in me, and I in him. 58 As the living Father hath sent me, and I live by the Father; so he that eateth me, the same also shall live by me. 59 This is the bread that came down from heaven. Not as your fathers did eat manna, and are dead. He that eateth this bread, shall live for ever. 60 These things he said, teaching in the synagogue, in Capharnaum.
61 Many therefore of his disciples, hearing it, said: This saying is hard, and who can hear it? 62 But Jesus, knowing in himself, that his disciples murmured at this, said to them: Doth this scandalize you? 63 If then you shall see the Son of man ascend up where he was before? 64 It is the spirit that quickeneth: the flesh profiteth nothing. The words that I have spoken to you, are spirit and life. 65 But there are some of you that believe not. For Jesus knew from the beginning, who they were that did not believe, and who he was, that would betray him. **