Written in a stern and troubled tone, its purpose was to counter certain theological movements which Pope Paul perceived were gaining ground in the Roman Catholic Church.

Using terminology such as "pastoral concern" and "anxiety", the letter sends a direct and unequivocal message to the church regarding the Eucharist.

To emphasize the centrality of the Eucharist in the church, the Pope echoed the words of Ignatius of Antioch, referring to the Blessed Sacrament the "medicine of immortality".

Paul VI felt very strongly that certain theological currents were threatening several Catholic doctrines and practices including: Pope Paul VI in the opening of the letter declares the following teachings are impermissible: "These and similar opinions do great harm to the faith and devotion to the Divine Eucharist.

And therefore, so that the hope aroused by the Council, that a flourishing of Eucharistic piety which is now pervading the whole Church, be not frustrated by this spread of false opinions"