It is known or somewhat, known some of the cartels cannibalize their victims like in training camps where victims that don't want to join them or perform certain tasks(because of their tasks) they cannibalize them. Also some of the higher ups in Los Zetas would shave their victims and prepare them in popular food dishes like tamales or tostadas. I heard from annectodal evidence that the leaders of Los Zetas like El Verdugo or Z-3 would cannibalize their rivals/victims in foods.