More: Vatican bans use of gluten-free holy bread during Mass - Independent.ie (11. July 2017)Holy Communion bread must not be gluten-free, the Vatican has ruled. In a letter to bishops worldwide, Cardinal Robert Sarah ruled the unleavened bread can be made with genetically modified organisms, but cannot be entirely gluten-free.
However, the Coeliac Society of Ireland has moved to reassure its members that low-gluten holy bread is safe to take – following the new guidelines by the Church.
I suppose if it's an issue, one could ask to trade the bread for a second glass of wine?