explanation of transubstantiation and the celiac

http://www.catholicbookwriter.com/goldenarrow/catholic/catholic-celiac-conundrum/

here is a partial quote:

How can a transubstantiated host, which is no longer bread, still act like wheat in the human body?
While the entire substance of bread has indeed been transubstantiated into the entire substance of Christ (Body, Blood, Soul, Divinity) such that the bread and wine cease to exist, their appearances remain, and those appearances act upon the senses just as the substance that they properly belong to naturally would. We sometimes say that Body and Blood of Christ are veiled by the appearances of bread and wine but ‘appearances’ means more than just what we see. The metaphysical term that the Church has employed to more accurately define ‘appearances’ is ‘Accidents’, which means those nonessential properties^[10] that exist in another thing. So those remaining (or attached) appearances (or accidents) belonging to wheat and wine do act upon the senses, are measurable, and do bring about the effects natural to the substance to which they belong. So the Eucharist looks like bread and wine, tastes like bread and wine, and acts like bread and wine, but in substance it is fully Christ and Christ only.

also here  http://www.stanthonymessenger.org/AskAFranciscan/Question.aspx?question=25  :


Why Do We Need Low-gluten Hosts?

I don’t understand why someone who has celiac disease and is, therefore, allergic to gluten needs a low-gluten host. The bread at Mass changes substantially into the Body of Christ. Clearly there is no gluten in flesh. The use of low-gluten hosts suggests to me that there is a lack of faith in the Real Presence of Jesus in the Eucharist.

Answer

I’m afraid you misunderstand what the Church teaches about the Real Presence of Jesus in the Eucharist. The Catholic Church’s teaching on transubstantiation was officially adopted at the Fourth Lateran Council in 1215 to explain in the terms of scholastic philosophy what the Church had already believed for centuries.
Those terms spoke of substance and accidents. The substance is what something radically is. The accidents are things like weight, color, shape or taste—things that can vary. Not all bread has the same accidents but it can be recognized as bread because it shares the same substance.
In the case of the Eucharist, the substance of bread is replaced by the substance of Christ’s body and blood. The accidents, however, are unchanged. A host does not change weight, color, shape, smell or taste after it has been consecrated. Similarly, the wine has the same weight, color, smell, taste and alcohol content after it has been consecrated at Mass.

If a host contains gluten before it is consecrated, then it will contain gluten after it has been consecrated. Because of that, a person allergic to gluten will have the same reaction to any host that contains gluten—whether it is consecrated or not. For this reason, some people—including Archbishop Dennis Schnurr of Cincinnati—need low-gluten hosts.

see also : http://en.wikipedia.org/wiki/Eucharist_in_the_Catholic_Church  and

http://www.adoremus.org/CDF_Lowgluten-mustum2003.html