Listen up all you absolutists:  You may have already have engaged in 'cannibalism' and you may never know...or you may eventually know.

Every human on earth has certainly ingested and inhaled some human derived exfoliated tissue at least.  That would be dead tissue shed from other humans.

Basically no complex molecules make it through the very harsh digestive tract or the well protected mucus membranes of the respiratory system in tact (whether in trace amounts or via straight-up cannibalism for that matter.)  A transfusion, OTOH, is a different matter all together.  Anyone who has had one is a 'cannibal' of historically extreme proportions.

On a related note, many/most humans have actual living cell lines from their mothers left over from gestation.  To a more limited degree if any, from their grandmothers as well.

It is also the case that a lot of vaccines were cultured in human cell lines.  One example is WI-38.  The 'WI' part stand for 'Wistar Institute'.  Although the unnamed person/embryo did not make it through gestation, she/it ended up being one of the most successful entities in history at replicating her/it's DNA.  This is what all DNA strives for (in my interpretation of biology at least.)

So, a corollary to 'you are what you eat' would be augmented by 'you are what you are injected with'.  In neither case do you probably know with certainty the facts of the matter.