... This [i.e. holding the host with both hands] is certainly the most natural practice and it is followed by the overwhelming majority of priests worldwide. Holding the host and chalice in both hands allows for greater pause, reverence and composure in carrying out this rite. As our reader points out, holding up the host with one hand can evoke an impression of nonchalance on the part of the priest with respect to the Eucharist.
On the other hand this practice is perfectly justified when a priest is physically impeded, as was the case of Pope John Paul II who held up the host with one hand when he could no longer control both members. In such a case any lack of aesthetics is more than compensated for by the priest’s devotion to his ministry edifying and nurturing the faithful ...