With all the hormones and whatnot inside. Dopamine, adrenaline, melatonin, whatever. Also, there’s this Hunter S. Thompson bit on the… pineal gland?
If it had an effect on you, wouldn’t it be a really messed up high, all over the place? With uppers, downers etc mixed? (Not including the emotional implications of eating raw human brains.)
And Chronic Wasting Disease (CWD) in cervids such as deer, moose, and elk, which thankfully has not been shown to be transmissible to humans yet. Prions are the stuff of nightmares.
Oh, and Fatal Familial Insomnia.