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.)
It’s a prion disease. Mad Cow, Creutzfeldt-Jacob, Chronic Wasting (so far only seen in deer), and Scrapies (known of for a long time and so far limited to sheep and goats) all start with a misfolded protein and gradually break down the brain till it looks like a sponge.
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.