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.)
The liver “conjugates”/metabolises a bunch of stuff, its been almost a decade since I studied this stuff but bassically it will remove or add functional groups on/off a given compound. Most of what you eat heads straight to the liver for “processing” where food (and orally administered drugs) get altered prior to circulation. Its part of the first pass effect.