The sacrament of the Eucharist has its basis on the words of Jesus, do this in memory of me (1 Cor 11:24) and his death on the cross. He urged the faithful to receive him in the sacrament of the Eucharist: “Truly, I say to you, unless you eat the flesh of the Son of man and drink his blood, you have no life in you (Jn. 6:53, CCC 1384). In the liturgy of the Mass, Christ is really present under the species of bread and wine. “The Catholic Church has always offered and still offers to the sacrament of the Eucharist the cult of adoration, not only during Mass, but also outside of it, reserving the consecrated hosts with the utmost care, exposing them to the solemn veneration of the faithful, and carrying them in procession” (CCC 1378).

Eucharist was always a point of contention, often raising the crucial question how can bread and wine become Christ’s body and blood. In the late fourth century St. Ambrose retorts, “Cannot the word of Christ, which was able to make what was not from nothing, change (mutare) those things that are into what they were not?” (De Mysteriis 9.52). In the second century, Justin the martyr said, “We have been taught that the food that has been blessed [‘made Eucharist’] by the prayer of the word that originates from him … is the flesh and blood of the incarnate Jesus” (Apology, ch. 66). The church has always emphatically taught “Our Lord Jesus Christ, true God and man, is truly, really, and substantially contained under the appearance of these sensible things” (The Council of Trent’s Decree on the Eucharist, ch. 1; text in DH 1636).

In order to receive Christ in Eucharistic communion, one must be in the state of grace. If one is aware of having sinned mortally, s/he must receive the sacrament of penance before receiving communion. Communion with the Body and Blood of Christ increases the communicant’s union with the Lord, forgives his/her venial sins, and preserves him/her from grave sins. It also reinforces the unity of the Church as the Mystical Body of Christ. (CCC 1415-1416).

The mode of Christ’s presence under the Eucharistic species is unique. It is called real presence. It does not mean that Christ’s presence elsewhere is unreal. The Eucharistic presence is real in the fullest sense. That means, it is a substantial presence by which Christ, God and man, makes himself wholly and entirely present (CCC 1374).