The early Church Fathers understood what the Eucharist meant.
“They abstain from the Eucharist and from prayer, because they confess not the Eucharist to be the flesh of our Saviour Jesus Christ, which suffered for our sins, and which the Father, of His goodness, raised up again” Ignatius of Antioch,Epistle to Smyrnaeans,7,1(c.A.D. ),in ANF,I:89
“For not as common bread and common drink do we receive these; but in like manner as Jesus Christ our Saviour,having been made flesh and blood for our salvation,so likewise have we been taught that the food which is blessed by the prayer of His word,and from which our blood and flesh by transmutation are nourished,is the flesh and blood of that Jesus who was made flesh.” Justin Martyr,First Apology,66(A.D. 110-165),in ANF,I:185
“[T]he bread over which thanks have been given is the body of their Lord, and the cup His blood…” Irenaeus,Against Heresies,IV:18,4(c.A.D. 200), in ANF,I:486
“Having learn these things, and been fully assured that the seeming bread is not bread, though sensible to taste, but the Body of Christ; and that the seeming wine is not wine, though the taste will have it so, but the Blood of Christ; and that of this David sung of old, saying, And bread strengtheneth man’s heart, to make his face to shine with oil, ‘strengthen thou thine heart,’ by partaking thereof as spiritual, and “make the face of thy soul to shine.” “ Cyril of Jerusalem,Catechetical Lectures,XXII:8(c.A.D. 350),in NPNF2,VII:352
“You will see the Levites bringing the loaves and a cup of wine, and placing them on the table. So long as the prayers and invocations have not yet been made,it is mere bread and a mere cup. But when the great and wonderous prayers have been recited, then the bread becomes the body and the cup the blood of our Lord Jesus Christ…When the great prayers and holy supplications are sent up, the Word descends on the bread and the cup, and it becomes His body.” Athanasius,Sermon to the Newly Baptized,PG 26,1325(ante A.D. 373),in ECD,442
Jesus told Nicodemus that he must be born again, not physically but spiritually. He must undergo a supernatural rebirth. And if he is a new supernatural creature then he would require supernatural food, the body and blood of the savior, the Eucharist.
John 3:3-6 Jesus answered and said unto him, Verily, verily, I say unto thee, Except a man be born again, he cannot see the kingdom of God. Nicodemus saith unto him, How can a man be born when he is old? can he enter the second time into his mother’s womb, and be born? Jesus answered, Verily, verily, I say unto thee, Except a man be born of water [Baptism?] and of the Spirit, he cannot enter into the kingdom of God. That which is born of the flesh is flesh; and that which is born of the Spirit is spirit.