[Unam Sanctam]

I think they are low gluten hosts. Totally gluten free would not be valid matter, as I understand it.

[Mrs. Don-o]

To be valid, the host has to be real wheat and only wheat. Of course there are different wheat cultivars, and they use the lowest-gluten kind.

Not sure, though, whether it is theoretically possible to have a wheat variety which is real wheat, but with no gluten. I suppose you'd have to refer to a distinctive, identifiable wheat genome, which wouldn't even have been an issue for most of the Church's history.