In Holy Communion, we are eating the True Body and Blood of Jesus Christ, without which "you shall not have life in you" (John 6:53).
The Catechism of the Catholic Church, 1333, tells us that; “At the heart of the Eucharistic celebration are the bread and wine that, by the words of Christ and the invocation of the Holy Spirit, becomes Christ’s Body and Blood. Faithful to the Lord’s command the Church continues to do, in his memory and until his glorious return, what he did on the eve of his Passion: “He took bread…,” “He gook the cup filled with wine…” The signs of bread and wine become, in a way surpassing understanding, the Body and Blood of Christ.”
It is appropriate, before one receives Holy Communion, to bow before the Sacred host or Chalice. This is because the bread and wine have truly become the Body and Blood of Jesus Christ. The priest or minister will say “The Body of Christ” or “The Blood of Christ”, after which we respond “Amen,” and receive the Body of Christ, consuming it immediately. When receiving The Blood of Christ, we drink, holding the chalice reverently and then return it to the priest or minister.