John puts the words "flesh" and "blood" in Jesus' mouth while the other evangelists and Saint Paul used "body" as the Eucharistic word. The word "flesh" is older and refers to the Hebrew basàr, always traslated by the Septuagint with the Greek sàrx, which refers not only to the fleshy part of the body, but also to the whole individual, the whole being, the whole person. The biblical expression "every flesh" indicates human beings in their wholeness, in all of their manifestations and ways of doing and being; to "eat the flesh" of Jesus, therefore, means to be nourished by the wholeness of His human and divine person. John meant that eating-drinking the flesh-life-blood of Jesus will be the only way for us to stay with Him, and for Him to stay with us.
Jesus talked about his flesh and his blood, as to say about His whole being and way of being, as food and drink, placing the adjective, true, next to the terms food and drink
Alethés, “true,” also means “valid, right way, inner rule, truthfulness, matter-of-fact reality.” Etymologically it means: “that which is not hidden.” The Indo-European root of alethès is ladh, from which the Latin làteo, “be hidden” and the Greek root lath-/leth-, “stay hidden” come. The Greek adverb làtre means “covertly, secretly.” In Akkadian we find the word latum, “cover,” that reappears again in the Hebrew root lwt, “cover, hide from the view of others.” Alethès means “what can be attested to after having witnessed,” the truth in the sense of “without lies and deception.” Indeed the adjective alethès refers to someone to whom things have not been hidden and who, remembering, can truly attest; someone who is true, sincere. He is true, sure, reliable, He is the effective reality opposing the concept of facade and appearance. He is what is solid, authentic, trustworthy, the person who deserves loyalty, He is the authentic being, He is the truth, the reality.
In this respect Jesus states and announces to humanity that all other foods, all other forms of psychic and spiritual nuìourishment to which mankind make reference to are non-authentic, false, not-true, because they do not provide the useful and appropriate energy which we need. The other nourishments that mankind makes reference to are miserably delaying and weakening at every level all real possible evolution towards a life that is truly evolved and noble.