Saint Augustine helps us to understand the dynamics of Holy Communion when referring to a kind of vision he had, in which Jesus said to him: "I am the food of the mature: grow, then, and you shall eat me. You will not change me into yourself like bodily food; but you will be changed into me"(Confessions, VII, 10, 18).
Therefore, while the bodily food is assimilated by the body and contributes to its maintenance, the Eucharist is a different bread: we do not assimilate it, but it assimilates us to itself, so that we become conformed to Jesus Christ and members of his body, one with Him.
Pope Benedict XVI
St Peter's Square 1 June, 2011