What is A2 milk?
Milk is a beneficial source of nutrition for us, as the proteins, fats, carbohydrates, vitamins and minerals it contains are essential for our body and helps it to function properly. Cow's milk is approximately 87% water, 5% lactose, 4% milk fat, 3.5% milk protein, minerals and vitamins.
The proteins in milk are:
Milk protein is mainly composed of caseins, within caseins we distinguish alpha (α), beta (β), gamma (γ) and kappa (κ) caseins. A2 milk is bovine milk that contains a particular form of β-casein in its protein content, called β-casein A2, instead of β-casein A1. A unit of β-casein in the protein content of milk is made up of a total of 209 amino acids, differing only in the 67th amino acid of the amino acid chain in the A1 and A2 forms. The A1 form of β-casein contains the amino acid histidine, while the A2 form contains the amino acid proline at position 67. This is a very small but very significant difference.
Amino acids responsible for A1 or A2 in milk β-casein
How is A2 milk produced?
A2 milk comes from cows with A2A2 genetic characteristics. Both parents had the gene A2, which encoded the amino acid sequence of ß-cases. Today, it is assumed that all cattle breeds originally carried A2 genetic material, and over time a spontaneous mutation (thousands of years ago with domestication) evolved the A1 gene. Slowly, the genetic state of European cattle breeds changed from A2A2 to A1A2 and A1A1. Today all three genetic combinations occur. This is why A2 milk is often called "original milk."
Today, almost all conventional milk and dairy products on the market come from cows with A1 and A2 ß-casein genes. Milk with more than 99 percent A2 ß-casein is identified and sold as A2 milk.
A2 milk is produced by Asian and African cattle as well as sheep, goats and buffaloes. What may be of interest to us is that breast milk is also A2 because it contains the amino acid proline at position 67 of the protein chain.
Why do many consumers swear by A2 "original" milk?
Several studies have found a link between the A1 form and the development of certain human diseases, and the reason for this is worth looking at the molecular level.
In A1 milk, the amino acid chain composition is changed compared to the "ancestral" milk, as A1 milk contains histidine instead of the proline found in A2 milk. As a consequence, proteases, the protein-digesting enzymes involved in digestion, will cleave (digest) the peptide chains at a different site. In A1 milk, after amino acid 59 and before amino acid 67. This results in a chain of 7 amino acids called BCM-7 or beta-casomorphin-7. This peptide has been associated with an increase in immune cell activity and inflammatory immune responses.
The BCM-7 peptide is also associated with a number of other negative effects, such as causing immune cell proliferation, respiratory dysfunction, negatively affecting the secretion of hormones needed for digestion in the stomach, increasing intestinal transit time, which may trigger inflammation in the digestive tract, and may also be involved in the development of inflammatory skin diseases.
When proline is found at amino acid 67, digestive enzymes can cleave sequences of different lengths. Of course, BCM-7 will also be produced, but in much smaller quantities, and peptides that are useful for our body can be produced in the process. As well as being easier to digest, A2 milk has many other beneficial properties.
As shown in the figure above, cleavage of A2 ß-casein can result in peptides that have immunomodulatory effects, can lower blood pressure, or even inhibit the development of enzyme-associated neurological disorders. Several literature has also linked A2 milk with a beneficial effect on type 1 diabetes, and that lactose intolerant people have fewer symptoms after drinking A2 milk, even though it has the same lactose content as A1 milk.
Science still has a lot of time and energy to invest in research into A2 milk before all its positive effects are known, but one thing is certain: people will need A2 milk in the future.
Re-establishing the A2/A2 dairy herd, restoring it to its original state
On our cattle farm we breed Holstein-Friesian cows, a breed with equal proportions of A1 and A2 ß-casein. The production of β-casein protein is determined by the combination of these two variants. On our farm, all three genetic variants are currently found in our cows.
Our breeding objective is to keep cows that only have the A2A2 gene, so that they only produce A2 type milk. In order to achieve our goals quicker, we are carrying out molecular genetic tests on the ear cartilage of all heifer calves. The laboratory carrying out the tests will determine the genetic status of the individual, including the type of β-casein present in the milk it produces, which will be officially certified.
Individuals carrying the A1 allele are culled and no longer bred. Our remaining heifers will only be bred to ß-casein A2A2 bulls, in the same way as our current cows.
The possible genetic combinations are as follows:
First A1A1 cows are disappearing from our herd, followed by A1A2 cows and finally we will have only A2A2 ß-casein producing cows. To achieve our goal we are working together with the Hungarian colleagues of the Canadian genetic company SEMEX.
It is a longer process. Until a pure herd is established, we will keep and milk our proven A2A2 cows in separate groups. This way we have pure A2 milk. As time goes on, the quantity of milk increases as the number of A2 cows increases. Before the milk is processed, we have the A2 status of the ß-casein tested by an official milk testing laboratory.