A1 and A2 milk
When I discovered that milk was off the menu for me I was encouraged to discover that some milk may be acceptable to people who were intolerant of standard cow’s milk. Goats, sheep and even some cows produce milk which has a different structure and providing lactose intolerance isn’t the problem, can be happily drunk. Welcome to the world of A1 and A2 milk.
The alternative milk is identified as A2. Originally all milk was A2 in structure – more details later – but somewhere between 5,000 and 10,000 years ago a genetic mutation occurred in cows that caused A1 milk. Thus, older breeds of cow produce A2 milk and newer breeds A1. Channel Island milk produced from Jersey and Guernsey cows can be A2 (I initially got the idea that all Channel Island milk is A2 but that is WRONG).
The first thing I did when I left work at the start of the summer holiday was buy a pint of gold top Channel Island milk and a big box of paper hankies. The milk tasted delicious but it was a good job I had the hankies because over the course of three days the nosebleeds started and got heavier.
Time for a bit more research!
A bit more research
Channel Island milk is not exclusively A2. Guernsey milk is nearly all A2 but Jersey milk has a lower percentage. A2 cows’ milk has to be selected for and it is available in the UK. (Link)
Milk is made up of two categories of protein: casein proteins which in cows is about 82% of total protein and whey protein (the other 18%). The A1 and A2 tags refer to a difference in one of the casein proteins.
Casein proteins come in alpha, beta and kappa forms and the crucial difference we are interested in lies on the beta form.
To understand this, I needed to understand some of the science behind proteins, their composition and digestion; so here goes…
Proteins are made up of amino acids, all of which have an amine group at one end and an acid group at the other. Between the amine and acid there is a carbon based chain which generally includes carbons, hydrogens, oxygens and nitrogens in varying amounts. There are 22 different amino acids that can be combined to make proteins, 21 of which are used by humans. See them here. 9 of the amino acids cannot be made by humans, have to be obtained from the diet and are termed essential.
More than two amino acids joined together is called a peptide unless more than 50 of them are joined when they are termed proteins. Protein chains are long enough to form linkages and to fold themselves up. The beta casein protein contains 209 amino acids joined together and the A1 version differs from the A2 in that the 67th protein is histidine not proline.
Digestion breaks the protein chain down into peptides which are called beta casomorphines or BCMs for short. BCMs are given a number to indicate how many amino acids are in the chain so BCM-3 refers to a peptide, beta casomorphine with 3 amino acids. The name “morphine” gives a clue about how they affect us when they bind to opioid receptors in our brain, spinal chord, gastrointestinal tract and other organs. Ideally the BCMs should stay within the gastrointestinal tract and only fully digested nutrients be allowed through into the bloodstream but leaky guts allow the particle to pass through and be transported around the body. According to drugabuse.gov the result is drowsiness, mental confusion, nausea, constipation and depressed respiration. A good thing that beta casein is only a tiny percentage of milk. Total protein in milk is slight over 3% with the remainder being water, fat, sugar and trace elements (here). 82% of that is casein and 30-35% of that is beta casein. The problem with beta casein is BCM-7 which is formed during the digestion of A1 milk and contains the histamine at position 67 on the chain.
Once the casomorphines have bound to opioid receptors in the body they are broken down into inactive dipeptides by an enzyme dipeptidyl dipeptidase-4. In the case of BCM-7 this releases histamine into the blood stream. The histamine is formed because histidine is only weakly bonded to the rest of the BCM-7 peptide.
BCM-7 has been called “the devil in the milk” and this is the title of a book of the same name by Keith Woodford,a New Zealand Dr, who noticed that patients with chronic illness were often intolerant of cow’s milk.