Milk allergies and intolerances are very common. Some people may find it comforting that though they cannot tolerate common grocery store cow dairy, they have no problem with goat and sheep dairy products. One reason may be the difference in the proteins. Allergies and intolerances to dairy are a reaction to one or more of their different proteins. One protein in milk that seems to be a common problem is A1 beta casein. The most common forms of beta casein are A1 and A2. Thousands of years ago all cows had A2 beta casein. Cow milk can be composed of all A2, all A1 or a hybrid of A1 and A2. Grocery store milk in the US is either A1 or a hybrid, unless it says otherwise. All sheep, goat, water buffalo and human milk are made A2 beta casein. A genetic mutation caused one amino acid to be changed from proline to histidine. This one mutation causes A1 beta casein to be digested or broken down differently in the gut than A2 beta casein. Here in lies the problem.
The digestion of A1 beta casein in the gut forms a product called beta-casomorphin-7 (BCM-7). BCM-7 is a powerful opiate linked to negative health effects. This protein is highly inflammatory for some people. A1 casein can contribute to gastrointestinal issues like irritable bowl syndrome, leaky gut, colitis and Chrohn’s disease. It can also possibly cause acne, eczema, constipation, asthma, excessive mucus formation in the respiratory tract and trigger or aggravate autoimmune diseases.
These symptoms occur because BCM-7 is an opioid peptide that can potentially activate opioid receptors throughout the body. Opioid receptors are important regulators of gastrointestinal motility. A1 beta casein can mimic effects of opioid drugs, possibly leading to constipation. Many immune cells express opioid receptors, which can lead to the immune system attacking the A1 beta casein. This abnormal activity of the gut’s immune system is what can lead to a food allergy/intolerance or more seriously an autoimmune diseases of the gut lining, like inflammatory bowl disease. BCM-7 also causes inflammation in the gut, which long term can lead to intestinal damage and leaky gut. The inflammation pathways activated by BCM-7 are the same as the ones involved with asthma. Therefore BCM-7 can be seen as an allergen promoting asthma in some people. More studies are needed to fully understand the mechanisms behind the increase in milk allergies and effects BCM-7 has on the human body. This could be why some people tolerate goat and sheep milk, cheeses and yogurt, but not our standard cow milk sold in the US.