What is A2 Milk Made From? The Truth Behind the Protein

November 28, 2025 •

4 min read

Originally, all cow's milk was of the A2 type, but a genetic mutation several thousand years ago introduced the A1 protein found in most modern dairy. Today, A2 milk is made from specially selected cows that naturally produce only the A2 beta-casein protein, avoiding the more common A1 variant.

Quick Summary

A2 milk comes from cows genetically selected to produce only the A2 beta-casein protein, rather than the A1 protein found in most conventional milk. This distinction can influence digestion for some individuals. The production involves careful genetic testing and herd management to ensure purity. The A1 variant emerged from a historic genetic mutation in European cattle breeds.

Key Points

Source of A2 Milk: It is made from cows that are genetically tested and selected to produce milk with only the A2 beta-casein protein.
Genetic Difference: A2 milk avoids the A1 protein, a variant that arose from a genetic mutation in some cattle over time.
Digestive Comfort: For individuals sensitive to the A1 protein, A2 milk may be easier to digest and cause fewer symptoms like bloating and discomfort.
Avoids BCM-7 Peptide: The A1 protein can break down into the peptide BCM-7 in the gut, which is associated with digestive issues, while A2 protein does not.
Not Lactose-Free: A2 milk still contains lactose, so it is not suitable for individuals with a confirmed medical diagnosis of lactose intolerance.
Specific Cow Breeds: Breeds like Jersey, Guernsey, and certain indigenous Indian cattle are more likely to be natural producers of A2 milk.

The Genetic Distinction of A2 Beta-Casein

The fundamental difference in what is A2 milk made from lies in the beta-casein protein content, which is determined by a cow’s genetics. Most conventional milk in Western countries contains a mixture of two beta-casein types, A1 and A2, due to a historic genetic mutation. This mutation, believed to have occurred in European cattle breeds between 5,000 and 10,000 years ago, altered a single amino acid in the protein chain. Consequently, A1 beta-casein breaks down differently in the gut compared to its A2 counterpart.

In contrast, A2 milk comes from cows that have been specifically selected and tested to ensure they only produce the A2 beta-casein protein. Farmers manage their herds to keep A2-producing cows separate, and the milk is processed independently to prevent cross-contamination. This process ensures the final product is free from the A1 protein.

How Milk Protein Affects Digestion

When A1 protein is digested, it can release a peptide called beta-casomorphin-7 (BCM-7). This peptide has been linked in some studies to digestive issues such as bloating, discomfort, and altered gut motility. In sensitive individuals, this can manifest as symptoms similar to lactose intolerance, though the issue is with the protein, not the milk sugar (lactose). A2 milk, on the other hand, does not release BCM-7 in the same manner, making it potentially easier on the digestive system for those sensitive to the A1 protein.

Cow Breeds That Produce A2 Milk

Certain cow breeds are naturally more likely to produce milk with a higher proportion of the A2 beta-casein protein.

Jersey: Jersey cows are known for their A2 milk genetics.
Guernsey: Guernsey cows have a high prevalence of the A2 gene.
Charolais: This breed is another common source for A2 milk.
Limousin: French Limousin cattle are among those typically associated with A2 production.
Indigenous Indian Breeds: Traditional Indian breeds are known to be naturally high in A2 beta-casein.

A cow's ability to produce A2 milk is a genetic trait, not dependent on its breed alone. Genetic testing is required to build a certified A2 herd.

The Difference in Digestion and Production: A Comparison


Feature	Conventional Milk (A1 + A2)	A2 Milk (A2 only)
Beta-Casein Protein	Contains a mix of both A1 and A2 types.	Contains only the A2 type.
Genetic Origin	Found in most modern herds, especially European breeds like Holstein.	Derived from heritage breeds and genetically tested cows.
Digestion Byproducts	May release the peptide BCM-7, potentially causing digestive issues.	Does not release significant BCM-7, making it gentler on the stomach for some.
Production Method	Standard large-scale dairy farming without genetic testing for protein.	Requires genetic testing of cows and careful herd separation.
Prevalence	The most widely available milk in grocery stores.	A niche, premium product typically sold at a higher price point.

The Science Behind A2 Milk's Gentle Digestibility

While A2 milk is often marketed for its potential digestive benefits, the science focuses on the molecular difference between the A1 and A2 proteins. The amino acid chain in A1 beta-casein has a histidine at position 67, while A2 has a proline. This difference affects how digestive enzymes interact with the protein. The proline structure of A2 protein resists the cleavage that releases BCM-7, an opioid agonist. BCM-7 can influence gut motility and inflammation by interacting with opioid receptors. For some individuals, this effect causes symptoms like gas, bloating, and discomfort often misattributed to lactose intolerance. By eliminating the A1 protein, A2 milk avoids this BCM-7 release pathway. Studies have shown some individuals with milk sensitivity experience less discomfort and improved gut health with A2 milk.

Conclusion: Understanding the A2 Difference

What A2 milk is made from is a specific type of cow with a particular genetic profile. It is a natural product from cows that produce only the A2 beta-casein protein, distinguishing it from most conventional milk that contains both A1 and A2 proteins. This genetic difference in protein structure is at the heart of the health claims surrounding A2 milk, particularly its potential to be easier on the digestive system for sensitive individuals. While not a cure for true lactose intolerance or a cow's milk protein allergy, A2 milk offers a natural alternative for those seeking to minimize potential digestive discomfort from the A1 protein. Its production relies on careful herd management and genetic testing to ensure purity. For those who experience mild digestive issues with standard dairy, trying A2 milk could be a simple, effective change for better gut comfort.

The Journey to A2

The Genetic Mutation: A genetic mutation in European dairy cattle created the A1 variant beta-casein protein.
Genetic Testing: A2 milk producers test cows to ensure they carry the A2 protein gene.
Pure Herds: Cows producing A2 milk are kept separate to prevent cross-contamination.
Processing: A2 milk is processed separately to maintain purity.
Marketing: Companies like the a2 Milk Company market this as a gentler dairy option.
Digestive Comfort: The absence of the A1 protein and its BCM-7 byproduct may lead to fewer digestive symptoms for some.

Frequently Asked Questions

A2 milk is produced by specially selected cows that are genetically tested to carry only the A2 beta-casein protein gene. Certain breeds, such as Jersey, Guernsey, and some indigenous Indian breeds, are more likely to be A2 producers.

No, most conventional cow's milk on the market today is a mix of both A1 and A2 beta-casein proteins. A2 milk is a specialized product that comes from herds of cows that have been specifically bred and selected to produce only the A2 protein.

No, A2 milk is not made with special additives or hormones to change its protein composition. The difference is entirely genetic; it is a naturally occurring protein type produced by certain cows.

Some people report fewer digestive issues, such as bloating and gas, when drinking A2 milk because it lacks the A1 protein. The A1 protein can break down into a peptide called BCM-7 during digestion, which is believed to cause discomfort in sensitive individuals.

No, A2 milk is not lactose-free and contains the same amount of lactose as regular milk. Therefore, it is not a solution for individuals with clinically diagnosed lactose intolerance.

To produce A2 milk, dairy farmers use genetic testing to identify and select cows with the A2 beta-casein gene. The milk from these herds is then kept separate from other milk during processing to ensure its purity.

Aside from the difference in beta-casein protein, the overall nutritional profile of A2 milk is very similar to conventional milk. It contains the same amounts of lactose, fat, vitamins, and minerals.