This is just a small thesis of mine, but I think the whole cannibalization deal was created to influence pagans to join the christian movement. At the time, sacrificial offerings were all the rage with the Roman belief system. Whether Jesus had the foresight to add this bit of persuation to his preachings or whether it was added later, I do not know, but it makes a bit of sense. Most religions(at the time) felt the need to please their gods by sacrificing something of worth. Is not their spiritual leader the highest offering possible? This bit of dogma made the transition from Paganism to Christianity simpler by adhering some similar traits.
Another example of the Christians's use of this persuasive tactic is Christmas, previously Saturnalia (where there was much "merriment") on the Winter Solstice(coincidentally close to Dec. 25'th? I think not). They had no clue when Jesus' birthday was, so they converted a Pagan holiday and included several of its practices:caroling, mistletoe,the candle procession(think Midnight Mass) and gift giving, to name a few(If anyone can think of anymore, I'd be happy to add them).
I will concede that it is more than possible that the pagans might have added some of these ideas/traditions after they had converted, and caused the current holiday amalgamation. Inevitably, we will never know the true origin and which came first, the practice or the pagans. Who is John Galt?.