I cannot find any RCT about this, I’ve only heard of mechanistic data, but that is independent of the dose. Yeah sure casomorphin attach to opioid receptors, but that doesn’t mean that it’s addictive, it’s dependent on the dose, for example you could give a person such a small amount of cocaine that they wouldn’t even notice it. So does the dose found in cheese have any influence on how addictive cheese is?
casomorphin is a peptide. in normal conditions peptides are converted into amino acids by enzymes in the gut and then the amino acids get into the bloodstream. but peptides can exert their effect on the site. like casomorphin can bind to opioid receptor in the gut and slow down motility, for example. so even if some peptides escape digestion and get into the bloodstream it is so insignificant you shouldn’t even think about it