In the parables that use the phrase eating of the flesh, or drinking of the blood, the spiritual understanding must be sought out .
The Leviticus 26 offering .
And ye shall eat the flesh of your sons, and the flesh of your daughters shall ye eat.And I will destroy your high places, and cut down your images, and cast your carcases upon the carcases of your idols, and my soul shall abhor you. Lev 26:29
To drink the blood of Christ is a way of saying Christ gave His Spirit life in jeopardy of His own Spirit life.
God is Spirit and not a man as us. Christ said of His own flesh it profits for nothing. It is the Spirit of Christ that does quicken ours souls giving us His understanding.
Joh 6:63 It is the spirit that quickeneth; the flesh profiteth nothing: the words that I speak unto you, they are spirit, and they are life.