The meaning is, as Otto says in his note, “that the divine food passes away into our bodies entire, so that nothing remains:”  and Dr. Pusey seems to take the same view, in his note on the words, “from which (food) through transmutation our blood and flesh are nourished:  “i.e. the material parts are changed into the substance of the human body Real Presence, p. 144.  See note 8, below..”