This petition, with the responsibility it involves, also applies to another hunger from which men are perishing: "Man does not live by bread alone, but . . . By every word that proceeds from the mouth of God," that is, by the Word he speaks and the Spirit he breathes forth. Christians must make every effort "to proclaim the good news to the poor." There is a famine on earth, "not a famine of bread, nor a thirst for water, but of hearing the words of the LORD." For this reason the specifically Christian sense of this fourth petition concerns the Bread of Life: the Word of God accepted in faith, the Body of Christ received in the Eucharist.
Source: Catechism of the Catholic Church (Vatican.va)