Whether some part of the food is changed into true human nature?

Objections

Objection 1 : It would seem that none of the food is changed into true human nature. For it is written (Mt. 15:17): "Whatsoever entereth into the mouth, goeth into the belly, and is cast out into the privy." But what is cast out is not changed into the reality of human nature. Therefore none of the food is changed into true human nature.
Objection 2 : Further, the Philosopher (De Gener. i, 5) distinguishes flesh belonging to the "species" from flesh belonging to "matter"; and says that the latter "comes and goes." Now what is formed from food comes and goes. Therefore what is produced from food is flesh belonging to matter, not to the species. But what belongs to true human nature belongs to the species. Therefore the food is not changed into true human nature.
Objection 3 : Further, the "radical humor" seems to belong to the reality of human nature; and if it be lost, it cannot be recovered, according to physicians. But it could be recovered if the food were changed into the humor. Therefore food is not changed into true human nature.
Objection 4 : Further, if the food were changed into true human nature, whatever is lost in man could be restored. But man's death is due only to the loss of something. Therefore man would be able by taking food to insure himself against death in perpetuity.
Objection 5 : Further, if the food is changed into true human nature, there is nothing in man which may not recede or be repaired: for what is generated in a man from his food can both recede and be repaired. If therefore a man lived long enough, it would follow that in the end nothing would be left in him of what belonged to him at the beginning. Consequently he would not be numerically the same man throughout his life; since for the thing to be numerically the same, identity of matter is necessary. But this is incongruous. Therefore the food is not changed into true human nature.