Augustine of Hippo

For some things are joined to others in such a way as both to change and be changed, just as food, losing its former appearance, is both itself turned into our body, and we too are changed, and our strength is refreshed by it.b Further, a most subtle liquid, after the food has been prepared and digested in our veins, and other arteries, by some hidden channels, called from a Greek word, pores, passes through us, and goes into the draught.

Catena Aurea by Aquinas ↗

Bede

Do you not understand that everything entering from outside into a man cannot defile him because it does not enter his heart but his stomach, and is expelled into the latrine, purging all foods? All the passages of the Gospels among heretics and the perverse are full of scandals. …

On the Gospel of Mark ↗

Glossa Ordinaria

GLOSS.a It says therefore into his heart, that is, into his mind, which is the principal part of his soul, on which his whole life depends; wherefore it is necessary, that according to the state of his heart a man should be called clean or unclean, and thus whatsoever does not reach the soul, cannot bring pollution to the man. Meats therefore, since they do not reach the soul, cannot in their own nature defile a man; but an inordinate use of meats, which proceeds from a want of order in the mind, makes men unclean. …

Catena Aurea by Aquinas ↗