In other words, are the benefits of the Eucharist purely spiritual, pertaining to the soul?
It would seem fitting to me that if we are consuming and digesting physical flesh and blood, that the effects would likewise be physical.
The fathers seem to suggest this as well. See quotes below, Can anyone explain ?
[Christ] has declared the cup, a part of creation, to be his own Blood, from which he causes our blood to flow; and the bread, a part of creation, he has established as his own Body, from which he gives increase to our bodies."
Source: St. Irenaeus of Lyons, Against Heresies, 180 A.D.:
“So then, if the mixed cup and the manufactured bread receive the Word of God and become the Eucharist, that is to say, the Blood and Body of Christ, which fortify and build up the substance of our flesh, how can these people claim that the flesh is incapable of receiving God’s gift of eternal life, when it is nourished by Christ’s Blood and Body and is His member? As the blessed apostle says in his letter to the Ephesians, ‘For we are members of His Body, of His flesh and of His bones’ (Eph. 5:30). He is not talking about some kind of ‘spiritual’ and ‘invisible’ man, ‘for a spirit does not have flesh an bones’ (Lk. 24:39). No, he is talking of the organism possessed by a real human being, composed of flesh and nerves and bones. It is this which is nourished by the cup which is His Blood, and is fortified by the bread which is His Body. The stem of the vine takes root in the earth and eventually bears fruit, and ‘the grain of wheat falls into the earth’ (Jn. 12:24), dissolves, rises again, multiplied by the all-containing Spirit of God, and finally after skilled processing, is put to human use. These two then receive the Word of God and become the Eucharist, which is the Body and Blood of Christ.”
-"Five Books on the Unmasking and Refutation of the Falsely