A2 Milk

A2 Milk is milk which has a particular beta-casein protein structure. The alternative common type of cow's milk, "A1 beta-casein" has been linked in epidemiological studies to a wide variety of ailments including heart disease, Type-1 diabetes, autism, schizophrenia and eczema.

Over 90% of American dairy cows carry at least one copy of the A1 gene. Only cows with two copies of the A2 gene produce exclusively A2 milk.

Certain individuals who are sensitive to commercial (or even raw, A1) cow's milk report being able to drink and digest A2 cows milk without the digestive discomfort and allergic symptoms that they get from A1 milk.

A1 and A2 beta-casein are genetic variants of the beta-casein milk protein that differ from one-another by only a single amino acid; "proline" [1] in A2 milk and histidine [2]. Histidine is a precursor to histamine [3], a molecule that plasy an important role in immune system responses and allergic reactions and is associate with inflammation, irritation, redness and mucus production.

All mammalian milk, (from whales, mice, humans, goats, etc) produce a beta-casein similar to the A2 type with a proline" at the appropriate site, the only mammals that are know to have histidine anywhere among the amino acids in their milk are cows which carry the A1 mutation.

A1 beta-casein is associated with a small (thought to be 3-5%) increase in milk production. Consequently selective breeding over the past 3 centuries have tended to favor the mutant A1 form of the gene. A1 is now the most common type found in cow's milk in America, Europe (except France), Australia and New Zealand. An inexpensive genetic test for cows is available from a number of sources such as the UC Davis Veterinary genetics laboratory [4]

References

Devil In The Milk: [5]

A2 Beta Casein Reference Article: [6]