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.)
Melatonin also breaks down in your stomach. It’s absorbed through the mouth and tongue while chewing. After that, most of the rest is lost. That’s why Melatonin pills require higher doses to do anything. The medical science world is still split if any of the fancy melatonin you gobble up in all those gummies can cross the blood brain barrier at all.
So the same rules apply.
Overall its very inconsistent due to the first pass effect of the liver as well. Anything absorbed from the alimentary canal goes through the liver first and the liver is very effective at breaking down lost hormones.