Question:

The doctrine of transubstantiation is the one which refers to the fact that in the Eucharist both the Bread and the Wine change, in substance, into the body of Christ. This means that the Bread is no longer Bread and the Wine is no longer wine; it has the appearance or accidents, but in substance they no longer are what they were, now it is the body of Christ, so someone can affirm that what he eats is not bread and what he drinks is not wine.

The catechism of the Church of Rome says it in this way:

1374 ……In the most blessed sacrament of the Eucharist “the body and blood, together with the soul and divinity, of our Lord Jesus Christ and, therefore, the whole Christ is truly, really, and substantially contained” (Council of Trent: DS 1651). “This presence is called ‘real’—by which is not intended to exclude the other types of presence as if they could not be ‘real’ too, but because it is presence in the fullest sense: that is to say, it is a substantial presence by which Christ, God and man, makes himself wholly and entirely present” (MF 39).

1376 The Council of Trent summarizes the Catholic faith by declaring: “Because Christ our Redeemer said that it was truly his body that he was offering under the species of bread, it has always been the conviction of the Church of God, and this holy Council now declares again, that by the consecration of the bread and wine there takes place a change of the whole substance of the bread into the substance of the body of Christ our Lord and of the whole substance of the wine into the substance of his blood. This change the holy Catholic Church has fittingly and properly called transubstantiation” (DS 1642).

1413 By the consecration the transubstantiation of the bread and wine into the Body and Blood of Christ is brought about. Under the consecrated species of bread and wine Christ himself, living and glorious, is present in a true, real, and substantial manner: his Body and his Blood, with his soul and his divinity (cf. Council of Trent: DS 1640; 1651).

Now, having this as context, my criticism is not theological but practical, although it has theological consequences.
There is an illness called celiac disease (CD); in Wikipedia we find what this disease is:

“Celiac disease is an autoimmune disease characterized by chronic inflammation of the proximal part of the small intestine or jejunum, caused by exposure to gliadin, a plant protein from some dietary cereals, called gluten (a protein present in wheat, barley, rye, triticale, kamut, spelt and possibly oats—because of cross-contamination issues).”

Now the problem is that this protein is found in the bread or host for the Eucharist, and therefore it is not advisable for a person who suffers from this disease to receive communion because he will have problems with his gluten intolerance.

However, these people have not been abandoned by their church, and low-gluten or gluten-free hosts have now been developed so that they will not have physical problems when receiving the Eucharist.

In short, the question is: If the bread truly changes into the body and blood of Christ, people with celiac disease could eat the host without any problem because it is no longer bread, it has already changed. So why do they suffer the effects of gluten?

Answer:

In the sacrament of the Eucharist—as in every sacrament—we must distinguish the matter (bread and wine) from the form (the words of consecration by which the priest acts in the Person of Christ (In Persona Christi) through the intervention of the Holy Spirit. It is true, as you say, that after the consecration there is no longer bread and wine, but, as Saint Thomas Aquinas distinguishes, although the substance of the bread and wine is no longer there, but rather that of the Body and Blood of the Lord (this is precisely what is called “transubstantiation”), nevertheless, the accidents of the bread and wine remain, that is, the color, size, weight, taste, etc. Saint Thomas explains it this way:

It is evident from the testimony of the senses that, after the consecration, the accidents of bread and wine remain. And divine providence has wisely arranged this. First, because it is not customary among men, but rather a horrible thing, to eat and drink human flesh and blood, the flesh and blood of Christ are offered to us under the species of foods most frequently used by men, namely bread and wine. Second, so as not to expose this sacrament to the mockery of unbelievers, which would happen if we ate the Lord in his physical state. Third, so that the fact of receiving the body and blood of the Lord invisibly may increase the merit of our faith. (S. Th., III, 75, 5)

Therefore, if a priest were to consume a liter of consecrated wine (which is the blood of Christ), he could suffer the effects of alcohol, and a member of the faithful who ate two kilos of consecrated bread would be nourished bodily, since, because the accidents are preserved, those properties are also preserved. The point is that Jesus is truly, really and substantially in the Eucharist, but not in his own species (so that we would see him, touch him, etc.) but in another’s species (the species of bread and wine); that is why when we eat him we do him no harm, and when a host falls to the ground, Christ is not struck, etc., because this affects the accidents, which are what have contact with the exterior. (You can see these topics in the Summa Theologiae, Part III, questions 73-83.

Author: Fr. Miguel Ángel Fuentes.