there is no controversey about low gluten bread, but gluten free bread is an issue, mainly for the celiacs, since the bread used must be wheat and only wheat, and even wheat processed as very low (no such thing as no gluten wheat bread) is problematical for some celiacs. receiving the Precious Blood, from one of chalices other than the priest’s (which has had a particle of host added) is an option for those who do not also have a problem with naturally occuring sulfites in the wine. Yes, it does entail extra work and care by the sacristan and ministers, but it must be done so that the sacrament cannot be denied. we do have a celiac child in the current communion class so this will be the first time it is addressed,
Gluten-Free is INVALID matter for the Eucharist, there is no question about that.
Low-Gluten is valid matter and can be used when necessary for those who suffer from celiac disease. It is not licit to use Low-gluten Hosts for everyone. Just as it is not licit to use only Mustum at Mass when the chalice will be offered to the faithful.
So many priests do not like the extra effort necessary to keep one or five special hosts apart during Mass from the others. Not when the Chalice is usually available.
there are not many people who are actually physically unable to consume even a small amount of gluten and any alcohol.