And yet, there are denominations that label transubstantiation as blasphemy (if not heresy). Its obvious Christ was speaking in metaphor at the last supper, and commanded for future disciples to do so as a memorial service of sorts, and only after deep self-reflection of that individual's relationship with the Lord. The warning that those who partake of communion unworthily are guilty of the shed blood/broken body of Christ is what confuses a lot of people. It is intended to keep the act somber, serious, and respectful. Could He have said "this [symbolizes]/ is [like] my blood, which has been spilled for you", of course - but His infinite wisdom guided Him to not do so, for reasons likely humanity will never comprehend.