At the beginning of this paper I set out to discuss the Sacrament of Eucharist in Jn 6. Since these are semitic terms, I went back to the Old Testament to better understand the implications John had in mind. I looked at the Hebrew meanings of both words in the context of the Law, Covenant and Passover.
Flesh is used to describe the body of an animal or person.
Blood on the other hand had a deeper meaning. Life is in the blood and it belonged to God. According to the Law, a pious Jew could not eat blood because all life belongs to God. If he did eat blood, then he would be cut off from his people. Blood was also used to ratify the Sinai covenant and atone for sins.