 One of the main sources of protein fragments with opiate-like activity in the diets of autism patients are dairy products. The main dairy protein casing breaks down into casomorphins, which have been considered to be factors involved in the cause and exacerbation of symptoms in food allergy and eczema, diabetes, schizophrenia, postpartum psychosis, crib death, and autism. According to this opioid excess idea, the development of autism includes a genetic predisposition, early exposure to some kind of environmental stress that affect the gut, which may cause more of these casomorphins to leak into the blood, and then the brain, where they may play a role in the development of autism. But you don't know until you put it to the test. First of all, do these bovine casomorphins form in the human digestive tract when we drink milk? Doctors decided to stick tubes down into people's intestines to find out, and indeed considerable amounts of casomorphin were found. Okay, but do they get absorbed into the bloodstream? Yes, apparently so, but this study was on infants who naturally have leaky-ear guts. Do fully intact casein protein fragments make it into the bloodstream after infancy? Yes, even into adulthood, elevating levels in the blood for at least eight hours after consumption. And those with autism may have an especially leaky gut at significantly higher risk for abnormally high intestinal permeability, which may explain why the vast majority of autistic children may have antibodies in their blood to wheat and dairy proteins compared to a small minority of normal children. And based on allergy studies, even if an infant is strictly breastfed, they may still be exposed to bits of bovine milk proteins if the mother drinks milk as the bovine protein fragments can get into her blood, then her breast, then into her baby's body. But does it get into the baby's brain? Yeah, those with autism are more likely to suffer from leaky gut, but the so-called opioid excess theory depends on casomorphins not only getting into the bloodstream, but up into the central nervous system, the brain. And there's something called a blood-brain barrier that helps cordon off the brain. But when you examine the brain tissues of those with autism, the blood-brain barrier seems leaky-ear, too. And indeed, evidence for the presence of casomorphins within the brains of infants has since been confirmed, which again just makes sense. That's the whole presumed point of casomorphin opioids to affect the brains of babies so they crave the milk, cry out for the milk, strengthening the mother-infant bond, the cow-calf bond. That's what's supposed to happen. It's normal, natural. Okay, then why are casomorphins associated with disease? Well, this is normal and natural. This? Not so much. Human infants with evidence of higher baseline levels of bovine casomorphins in their blood seem more likely to be suffering from psychomotor delay, which is a measure of muscle language and mental function development. But the reverse was found for human infant exposure to human casomorphins, meaning human casomorphins appeared to be beneficial in humans. And just like bovine casomorphin levels in the baby's blood appear to rise after feeding cow's milk formula, human casomorphin levels rise in the baby after breastfeeding. And that's what's supposed to happen. The greatest baseline human casomorphins was revealed in breastfed infants with normal psychomotor development and muscle tone. In contrast, elevated baseline bovine casomorphins found in cow's milk formula-fed infants was associated with delayed psychomotor development and stiffened more rigid muscle tone. The explanation of the opposite of facts of human versus bovine casomorphins on infant development probably has to do with species specificity. Cow's milk is good for calves, breast milk is good for babies. Indeed, the structure of bovine and human casing is dramatically different, and the bovine and human casomorphins themselves are different molecules, compared by two amino acids, which result in greatly different potencies. Compared to human casomorphin, bovine casomorphin is highly potent and more similar to morphine in its effects. A two amino acid difference doesn't seem like a lot, but casomorphins are only seven amino acids long. This 30% or so difference likely defines the difference in their biological properties. Both human and bovine casomorphins interact with opioid and serotonin receptors, which are known to be of great importance for brain maturation, but cow casomorphin binds tighter to these receptors, and so has more of an effect. This can therefore help explain not only why breast is best, but the psychomotor delay linked with higher bovine casomorphin levels in the blood supports this concept that cow casomorphins may play a role in a disease such as autism. This is why bovine casomorphins have been called the devil in the milk, but are they formed from all cow's milk? What about so-called A2 milk? The A2 milk corporation points out that there are different variants of casing. Some cows produce milk with a kind of casing dubbed A1, and other cows produce milk with A2 casing, which differs from A1 casing by a single amino acid, but strategically located such that A1 casing breaks down into casomorphin, which acts like morphine and is implicated in digestive immune and brain development changes. But supposedly A2 milk does not put A1 milk on a test tube with some digestive enzymes, and the A1 casing breaks down into casomorphin. But because of that amino acid difference, the A2 casing breaks down at a different spot, and so no casomorphin is formed. But this was using digestive enzymes from pigs or cows, which are just cheaper and easier to buy for laboratory experiments. But human digestive juices are different, and so what happens in a pig stomach or cow's stomachs may not necessarily be what happens in the human digestive tract, but the A1 versus A2 breakdown experiment had never been performed with human enzymes before. Until now, human stomach and intestinal juices were collected, and the devil was in both. The opioid casomorphin was produced from both A1 and A2 milk, so A2 milk may be better for this babe, but not necessarily for this one.