Factsheet A2 milk

Factsheet A2 milk

Composition of milk

Standard European milk is about 87% water and 13% milk sugar (lactose), protein, fat and minerals. By comparison, Guernsey milk is 85% water and 15% solids.
In one liter of milk there is 35 gram protein which can be divided into 82% casein and 18% whey. The casein in cow’s milk can be divided into subtypes: alfa, kappa and beta. The beta casein comprises 30% of the total protein content in milk. It is this component of the milk protein that has been linked to several negative health effects.

Evolution of A1 and A2 milk

The two most common genetic variants of the beta casein gene are the A1 and the A2 variants. It is believed that the A2 variant is the ancestral form of the gene and in the past few thousand years, a natural genetic mutation occurred in some European dairy herds that changed the beta casein they produced.

The gene encoding beta casein was changed such that the 67th amino acid in the 209 amino acid chain (i.e. the beta casein protein) was switched from proline to histidine. This new kind of beta casein is known as A1 beta casein, and is generally more common in many of the big black-and-white cow breeds of European descent such as the Holstein and Friesian.

Predominance of A1 milk producing herds

Due to their size, milk production, and demeanor, these breeds of cow are used to produce the vast majority of Northern Europe and America’s milk, but they have a very high percentage of A1 genetics.
The only herd in Europe that produces A2 milk (the “safe” milk) is the Guernsey herd and, to a lesser degree, the Jersey herd. Also the African and Asian cows (the ancestors of the European cow), camels, buffaloes, goats and sheep produce “safe” A2 milk.

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A1 beta-casein explained

The problem with milk containing A1 beta casein is that the 67th amino acid switch from proline to histidiene readily allows a digestive enzyme to cut out a 7 amino acid segment of the protein immediately adjacent to the histidine.
The 7 amino acid segment that is separated from A1 beta-casein is known as beta-casomorphin-7, often abbreviated as BCM-7.
When proline is present in that location (as it is in A2 beta-casein), that same segment is either not separated at all or the separation occurs at a very low rate.

BCM-7 and disease

BCM-7 is the real “devil” in the A1 milk for a number of reasons. It is an exogenous (doesn’t naturally occur within the human body) opioid that interacts with the human digestive system, internal organs and brainstem. While no direct causal relationships have been demonstrated between BCM-7 and these illnesses, indigestion of BCM-7 has been linked to type 1 diabetes, heart disease, autism, and other serious diseases as well.

Laboratory research

In rodent experiments conducted at the AgResearch Institute in New Zealand, led by professor Keith Woodford, and the National Dairy Research Institute in India, led by Dr Mahammad Raies Ul Haq, it was demonstrated  that BCM-7 is likely to damage our digestive system. In mice a high percentage of inflammatory reactions in the small intestine were found after consuming milk, suggesting an allergic reaction.
The main counterargument is about the rats and mice. They are not people. However, the evidence of smoking being related to cancer and heart disease is all epidemiological plus laboratory investigations, and no clinical trials. It did take a long time before tha anti-tobacco people won the debate. They did so because of the enormous power of commercial forces.

A2 milk market share

In New Zealand and Australia A2 milk has now a market share of 9 percent and is still growing. It is on sale on the supermarket shelves alongside the A1 milk cartons. In Great Britain the A1 milk is also getting more and more prevalent, particularly in Northern England.


The production of A1 or A2 milk is determined by which variant of the beta-casein gene the cow carries.
The frequency of the two variants varies greatly between breeds, the most popular European breeds have a high frequency of the A1 gene, whereas the A2 variant is common in the Guernsey herd. The A1 variant occurred fllowing a genetic mutation and is broken down during digestion to release the harmful peptide BCM-7.

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