A1 and A2 beta casein proteins are made up of 209 amino acid chains. There is only one amino acid difference between the A1 amino acid strand compared to the A2 amino acid strand. This very small structural difference results in a big difference in the way the protein breaks down and is digested in our gut.
When the A1 amino acid chain breaks down it produces a peptide called BCM-7. BCM-7 (beta-casein morphin) is an opioid-like compound. In the human body, BCM-7 has been shown to slow down gut transit time (slows transport of food / digestion throughout the body) therefore can cause a change in bowel function, influence gut bacteria and inflammation in the gut. It is thought these changes can mean some individuals poorly tolerate milk.
A2 is the original beta-casein produced in cow’s milk. A natural mutation over a number of centuries occurred where cattle began to also produce A1 beta-casein, affecting mainly Holstein cows (cattle from European origin).
So, if you have been tested for milk allergy; it is likely for A1 casein because all dairies in the US are A1 milk. Here is a test you can do at home; stay away from all dairy for 2 weeks, then drink a big glass of A1 milk. Count the number of times you sneeze in an hour. You should not sneeze at all, any sneezing not cold related means you are allergic to A1 milk. Try the same with A2 milk, to date no one has been found with an allergy to A2 milk. Lactose intolerance is completely different and means you have a reaction to the sugar found in skim milk. There is little to NO sugar found in cream so if you are lactose intolerant as I am, place ice cubes in a tall glass and top with ice cold cream! No fear of this good omega 3 fat going to your waist, I have lost 65 lbs since dropping the diabetes diet and going on this high fat low carb with good protein diet as found is a BETTER plan and previous to BIG Pharma touting insulin to diabetics, this was the cure for diabetes.