Cheese is one of the most commonly craved foods, suggesting the possibility of opiate activity, as has been demonstrated with other craved foods, particularly chocolate. Like other dairy products, cheese contains casein, which is the major protein in cow's milk. This is unlike human milk, in which the primary protein is whey.

Casomorphin is an opioid peptide (protein fragment) derived from the digestion of the milk protein casein. Casomorphin is one of the opioid compounds formed in our stomachs when we drink milk.

The opiate-like casomorphins liberated from the cow’s milk protein, casein, are also accused of participating in the cause of other conditions including type I diabetes, postpartum psychosis, circulatory disorders, food allergies, and autism.

The researchers “report a case of a breast-fed infant with recurrent apnea episodes, which have always been preceded by his mother’s consumption of fresh cow’s milk.” Lab tests revealed a high level of casomorphin in the child’s blood, leading researchers to speculate that it was the “opioid activity that may have a depressive effect on the respiratory center in the central nervous system and induce a phenomenon called milk apnea.” Thus, some babies may just not be able to clear it out of their systems fast enough and are placed at risk for SIDS.

What keeps most vegetarians from going whole-hog vegan? Not eggs. It’s the cheese. The salty, fatty goodness that makes you salivate should you get even a tiny whiff. It’s just so good, many will say. Well, there’s more to the story. You may, in fact, be hooked, so to speak.

It turns out there’s a reason behind our cravings. Cheese contains casein. It also contains casein fragments called casomorphins, a casein-derived morphine-like compound. Basically, dairy protein has opiate molecules built in. When consumed, these fragments attach to the same brain receptors that heroin and other narcotics attach to. Basically, if milk is cocaine, then cheese is crack.

Our brain's ‘reward center’ releases dopamine when we eat salty foods like cheese in order to encourage us to eat more of it (many addictive drugs increase dopamine activity). Dopamine makes our bodies become attracted to whatever produced it,