At the last supper Jesus was addressing his 12 disciples and they were all Jews including Jesus. Jesus said “do this in rememberance of me” Of course he meant it in a symbolic way as the most horrific unclean act to a Jew would be drinking blood and eating human flesh. Jesus spoke in parables.
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“as the most horrific unclean act to a Jew would be drinking blood and eating human flesh.”
And those that would not eat or drink the flesh and blood - did not believe - and they did not follow Jesus.
Please read John 6 which provides a preview of the Last Supper and the establishment of the Sacrament of the Eucharist:
48I am the bread of life. 49Your ancestors ate the manna in the desert, but they died;z 50this is the bread that comes down from heaven so that one may eat it and not die. 51I am the living bread that came down from heaven; whoever eats this bread will live forever; and the bread that I will give is my flesh for the life of the world.”a
52The Jews quarreled among themselves, saying, “How can this man give us [his] flesh to eat?” 53Jesus said to them, “Amen, amen, I say to you, unless you eat the flesh of the Son of Man and drink his blood, you do not have life within you. 54Whoever eats* my flesh and drinks my blood has eternal life, and I will raise him on the last day. 55For my flesh is true food, and my blood is true drink. 56Whoever eats my flesh and drinks my blood remains in me and I in him. 57Just as the living Father sent me and I have life because of the Father, so also the one who feeds on me will have life because of me.b 58This is the bread that came down from heaven. Unlike your ancestors who ate and still died, whoever eats this bread will live forever.” 59These things he said while teaching in the synagogue in Capernaum.
The Words of Eternal Life.* 60Then many of his disciples who were listening said, “This saying is hard; who can accept it?” 61Since Jesus knew that his disciples were murmuring about this, he said to them, “Does this shock you? 62What if you were to see the Son of Man ascending to where he was before?* 63It is the spirit that gives life, while the flesh* is of no avail. The words I have spoken to you are spirit and life. 64But there are some of you who do not believe.” Jesus knew from the beginning the ones who would not believe and the one who would betray him.c 65And he said, “For this reason I have told you that no one can come to me unless it is granted him by my Father.”
66As a result of this, many [of] his disciples returned to their former way of life and no longer accompanied him. 67Jesus then said to the Twelve, “Do you also want to leave?” 68Simon Peter answered him, “Master, to whom shall we go? You have the words of eternal life. 69We have come to believe and are convinced that you are the Holy One of God.”d 70Jesus answered them, “Did I not choose you twelve? Yet is not one of you a devil?” 71He was referring to Judas, son of Simon the Iscariot; it was he who would betray him, one of the Twelve.e