“A2” refers to a specific molecular structure of the casein protein in milk. As it happens, human milk, goat milk and sheep milk all have casein protein that is entirely of this structure. Cows, when domesticated thousands of years ago also produced milk which had this structure. However a subsequent mutation affecting the Holstein and Friesian breeds (also thousands of years ago) changed the molecular structure of the casein protein in their milk, and this structure is “A1”. Today, after many years of inter-breeding, the milk from a cow may be entirely A2 (A2A2), entirely A1 (A1A1), or a combination of the two (A1A2). Because Holsteins are the dominant cow in American dairy, most cow’s milk products in the U.S. are entirely or predominantly A1.
The mutation that occurred and its specific nature is not a matter of dispute. However, the medical significance of this is a matter of some dispute. Keith Woodford, in his book Devil in the Milk, published in 2007 asserted that the A1 protein is implicated in an array of non-communicable diseases. In addition, it is believed that for some portion of the population (15%-20%) the A1 protein causes digestive discomfort.
At Crowley Cheese we cannot contribute to the scientific investigation of this issue. However, for many years before we learned about A2 protein in milk we have been confused by the many customers that we have had who were concerned about the discomfort that they associated with the lactose content in cheddar cheese. This never made sense to us because the fermentation process in making a cheddar (including Crowley cheese) should consume essentially all the lactose, leaving a naturally lactose-free cheese. Learning about the discomfort that may be associated with the A1 casein protein for some people was a logical explanation for what some number of people have been experiencing beyond any issues with lactose intolerance.
Jersey cows were, of course, originally A2A2, but with interbreeding over time, only testing each individual cow for production of A2A2 milk can confirm that it is not producing A1A2 milk. This testing was performed by Jersey Girls Dairy for its herd, and those cows who were not producing A2A2 milk were moved out of the herd and replaced with A2A2 cows. All of the Jersey milk cheese that Crowley has produced since the beginning of 2019 has been made with entirely A2A2 milk.
You can find additional information through the links below:
- “What is A2 Milk?” Bon Appétit, https://www.bonappetit.com/story/what-is-a2-milk
- “Milk Containing A2 β-Casein ONLY, as a Single Meal, Causes Fewer Symptoms of Lactose Intolerance…,” MDPI, https://www.mdpi.com/2072-6643/12/12/3855
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