All dairy cows create milk that is a good source of protein.  Milk proteins come in two types -- casein and whey.  Casein comprises about 80% of the protein in milk.

There are three different types of casein proteins - alpha, kappa and beta-caseins. Of these, beta-caseins comprise about 35% of the casein protein in milk or about 30% of the overall protein in milk.

Among beta-caseins, there are two prevalent types that appear in the milk of dairy cows --called "A1 beta-casein" and "A2 beta-casein".

The differences in the beta-casein content of the milk of various dairy cows is determined naturally. In the same way that people have different colored eyes and hair based on traits they inherit from their parents, dairy cows similarly pass on traits to their offspring that naturally determine the balance of beta-casein proteins in their milk. Thus, some cows naturally produce milk with A1 beta-casein and no A2 beta-casein, others naturally produce milk with A2 beta-casein and no A1 beta-casein, and some naturally produce milk with a combination of both.

For example, several studies have shown that among Holstein cows (the most common dairy cow in the U.S.), only about 25% have inherited the traits to produce milk with A2 beta-casein but without A1 beta-casein - or what we call "a2 Milk™".

To make a2 Milk™, we use proprietary processes to identify and seperate into herds just those dairy cows that produce milk with A2 beta-casein but no A1 beta-casein, so their milk can be gathered and bottled without containing any of the A1 beta-caseins commonly found in most other milks.

Both A1 and A2 beta-caseins in milk are proteins constructed from 209 amino acid units which are strung together in a common sequence to form a chain, with one key distinction at the 67th position in that chain.

In the case of A2 beta-casein, the 67th amino acid in the chain is “Proline,” in contrast to “Histidine,” the amino acid found in the same spot in A1 beta-casein protein chain.

Click the image below to enlarge.

Owing to this small structural difference in the amino-acid chains of the A1 and A2 beta-casein proteins, A2 beta-caseins can break down differently during digestion, creating different biologically active peptides for the milk drinker.

This distinction also allows us to test and certify that at least 99% of the beta-casein present in a2 Milk™ is the A2 type of beta-casein and that none of the beta-casein is the A1 type.

Click here to learn more about the science behind beta-casein proteins.