Bread made for celebrating the Eucharist must be unleavened and made solely from wheat flour mixed with water, according to the General Instruction of the Roman Missal.

This traditional norm creates problems for Catholics with gluten intolerance, such as those who suffer from Coeliac disease and for whom ingesting a host can trigger stomach pains, diarrhoea and lethargy.

Some Christian communities have sought to address the problem by making communion wafers from rice or potato flour, but this is not permitted in the Catholic Church as wheat must be a key ingredient – and wheat is a source of gluten.