If you've done research on raw milk, you may have come across references to A1 vs. A2 milk. Following the 2007 release of the book Devil in the Milk by Keith Woodford, there has been growing concern expressed by the general populace about A1 and A2 beta-casein content in milk. At Pasture's Delights, we recently tested our cows to find out our herd's A1/A2 beta-casein composition. Before we get into that, let us explain a little about what this means.

To understand the difference between A1 and A2 milk, you’ll need to understand some detail about the composition of milk, specifically the protein content. Cow milk contains about 3.3% protein. With milk protein there are two broad categories—whey and casein. The ratio of whey to casein varies greatly by species, but in cow breeds about 20% of the protein is whey and the remaining 80% is casein. Bovine casein protein comes in 5 varieties: Alpha-S1, Alpha-S2, Beta, Kappa, and Gamma. In one study of casein proteins in Ayrshire cows, 49% were Alpha Caseins, 36% were Beta Casein, and the remaining 15% were Kappa and Gamma Casein.

When we talk about A1 or A2 milk, we are only talking about Beta Casein and nothing else. Not fat or carbohydrates but only protein — and specifically a type of protein, Beta Casein, which accounts for just under 30% of the total protein content in milk. In a cup (236g) of our Ayrshire milk, we would expect about 2.3g of Beta Casein out of the total 7.8g of protein.

The Beta Casein protein is a long chain of 209 amino acids. The difference between A1 and A2 milk is a change between a single amino acid in this chain. In A1 milk the 67th amino acid in the chain is Histidine, while in A2 milk this amino acid is Proline. You might be asking yourself, why is this important at all?

The reason this may be important is that the Histidine amino acid bond in A1 milk is weaker compared to the Proline bond in A2 milk. During digestion the A1 Histidine bond is easily broken and creates an amino acid fragment call Beta Casomorphin 7 (BMC7). BCM7 is typically broken down further by the enzyme DPP4. Some individuals with certain health conditions (Crohn’s, Celiac, Autism) may have impaired digestion and not effectively produce this enzyme. BDM7 that is absorbed into the blood from the digestive track (most pronounced in individuals with leaky guts) can trigger cell inflammation and has been shown to bind to opioid receptors in the brain. However, rigorous scientific studies on the effect of BMC7 are few and far between and most use questionable epidemiological methodology that studies broad data sets to draw dubious correlations. This is the same process used in the controversial China Study, which concluded plant-based diets promote health and animal-based diets cause disease. Since we question these types of studies to draw accurate causation, the conclusions derived from the BMC7 studies are suspect as well.

BCM7 may be mainly created by A1 cow milk, but you should know that the digestion of casein protein in all milks including bovine, goat, sheep, and even human milk create various Beta Casomorphins. BCM4, 5, 6, 8, 9, 11, 13, and 21 are all produced as the 209 amino acids of the Beta Casein molecule are cleaved apart by enzymes during digestion. Most of these are quickly broken down further by enzymes, just like DPP4 does for BCM7 in most people without impaired digestion.

Also, interestingly enough, the Beta Casein in human breast milk is broken down into BCM7 as well. The only difference here is that breast milk only contains about 10-15% as much total beta casein as cow milk, and there are 2 amino acids that differ between the human and bovine versions.

One last factor to consider with A1 and A2 is the genetics behind it. The blueprint for the Beta Casein protein is encoded in a cow’s (and all mammal’s) genes. If you’re familiar with genetics, you know that genes come in pairs. Half are inherited from the father and half from the mother. The genes that encode for Beta Casein are the same and it is possible to have both an A1 and A2 gene. Cows can have A1/A1, A1/A2, or A2/A2 genetics. An A1/A1 cow will produce only A1 milk and an A2/A2 cow will produce only A2 milk. However, since neither gene is dominate, an A1/A2 cow will produce a blend with half the Beta Casein being A1 and half being A2.

When scientists first categorized the exact makeup of Beta Casein protein, the first one was numbered A1. Later a chain was discovered that had a difference in the 67th amino acid and it was numbered A2. Later when tracing back the genetics, it was discovered that the A2 gene was in fact the original and the A1 is a mutation that originated a few thousand years ago in European cattle. There have actually been a total of 12 bovine beta casein variants found that are offshoots of the original A2 gene including A1, A3, A4, B, C, D, E, F, G, H1, H2, and I.

Genetics can vary significantly by breed. For example Holsteins favor A1, Guernseys and to a lesser extent Brown Swiss favor A2, and Jerseys and Ayrshires fall in the middle. This was actually proven out when we recently invested in genetic testing. Our Herd consists of 8 A2/A2 cows, 8 A1/A1 cows, and the rest A1/A2. So in our original example of a cup of milk, our Aryshire milk would contain 50% A1 and 50% A2 Beta Casein.

Although it may be inconclusive as to the exact dangers of A1 milk and the resulting BCM7, we feel the precautionary principle should be invoked. Humans have been consuming cow milk for 10,000 years, but A1 milk and the BMC7 that comes with it are a relatively recent development. Only in very modern times with the supremacy of the Holstein breed in US Dairy (accounting for more than 90% of all dairy cows today) has so much A1 milk been consumed. Realistically fluid milk is a minor concern compared to A1 cheese where the lactose carbohydrate and whey protein components have been removed and the casein proteins are further concentrated. Imagine how this has become even worse in our ‘fat is bad’ culture where even the fat is also removed in low and no-fat cheeses leaving only the casein. For example 2 slices of fat-free American singles made from A1 dominant Holstein milk would likely have nearly 3g of A1 beta casein or more than 2.5 times the amount found in a cup of our raw milk.

As a business and raw milk producer, we recognize that the A1 vs A2 issue may be important to some of our current and future herd owners. We do have as part of our business plan a roadmap for converting the herd towards exclusively A2 milk, but this will be multi-year project. In the meantime we are asking individuals that desire an exclusive A2 offering to let us know. In order to help cover the cost of genetic testing, separate and segregated collection, and additional administration expenses, we will only be making the A2 milk available at a premium. Initially we plan to set the boarding fees for A2-only shares at $12/share/week, but we will only begin the new offering once we have enough shares committed (15+).

If this is beyond your means or you don’t feel A2 milk is worth this premium, don’t worry about the milk that you receive containing more A1. We are setting our current 50/50 A1/A2 ratio as the benchmark for our standard herdshare offering. We will suspend additional A2 shares if they would cause our average on remaining milk to fall below the current value until we add another A2/A2 cow to the herd. In all likelihood, the percent of A2 milk in all our milk will increase over time as we continue to convert the herd by testing and selecting for A2/A2 genetics.

If you would like to do additional reading about this subject, we have extra copies of Keith Woodford's Devil in the Milk we would be happy to loan you. Just request them with your next delivery.

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