Some people crave milk due to the opiod peptides contained in dairy products. Opiod peptides represent what are known as amino acid sequences. Opiod peptides impact the brain in a manner similar to opiates, like OxyContin and heroin.
Opiod peptides in milk target endorphin receptors, leaving a person feeling good. The manner in which the opiod peptides in milk interact with endorphin receptors renders this and other dairy products semi-addictive. Researchers surmise that this attraction is designed to draw infants to consume milk in order to maintain their heath. The semi-addictive quality of milk does not dissipate as a person ages.