Which cow's milk is A2 milk and what makes it different?

November 27, 2025 •

4 min read

A genetic mutation occurring thousands of years ago resulted in cows producing A1 beta-casein protein, but many traditional breeds still only produce A2 milk. This guide explains which cow's milk is A2 milk, detailing the specific breeds and the key differences in their protein makeup.

Quick Summary

A2 milk comes from specific cow breeds, primarily indigenous Indian and some European ones like Guernsey, which produce only the A2 beta-casein protein, potentially easing digestion.

Key Points

A2 vs. A1 Beta-Casein: A2 milk contains only the A2 beta-casein protein, while most conventional milk is a mix of A1 and A2 proteins.
Breed Matters: Certain cow breeds, like indigenous Indian varieties (Gir, Sahiwal) and European breeds (Guernsey, Jersey), are more likely to produce A2 milk.
Digestion Difference: The A1 protein can release a peptide (BCM-7) that some link to digestive discomfort, a reaction not associated with A2 protein.
Not a Cure for Lactose Intolerance: A2 milk is not a solution for lactose intolerance or milk protein allergies, as it still contains lactose and milk proteins.
Genetic Testing is Key: True A2 milk production relies on genetic testing and segregation of herds to ensure no A1 protein contamination.
Similar Nutrition: The overall nutritional profile of A2 milk is comparable to conventional milk, offering similar vitamins and minerals.
Personal Choice: The decision to switch to A2 milk depends on individual digestive response, as benefits are often person-specific.

The Genetic Origin of A1 and A2 Milk

Historically, all cows produced milk containing only the A2 beta-casein protein. However, a genetic mutation that occurred thousands of years ago in some European cattle led to the production of A1 beta-casein alongside the A2 variant. Today, most conventional milk on the market, especially in Western countries, contains a mix of both A1 and A2 proteins, with many breeds having both A1 and A2 genes. The key difference between these two proteins lies in a single amino acid at position 67 of the protein chain, which significantly impacts how they are digested and absorbed by the body.

A2 Beta-Casein and the Absence of BCM-7

The defining characteristic of A2 milk is the exclusive presence of A2 beta-casein protein. During digestion, the A1 beta-casein protein breaks down and can release a peptide called beta-casomorphin-7 (BCM-7). For some individuals, this BCM-7 peptide has been linked to digestive issues, such as bloating, gas, and discomfort. The structure of A2 beta-casein, on the other hand, prevents this release, resulting in a digestion process that is gentler on the gut for those sensitive to A1 protein. This is not the same as lactose intolerance, as A2 milk still contains lactose. The perceived digestive benefits of A2 milk are specific to protein sensitivity, not lactose sensitivity.

Cow Breeds that Produce A2 Milk

Different cow breeds have varying genetic profiles regarding beta-casein production. Some breeds are known for a higher prevalence of the A2A2 gene, meaning they exclusively produce A2 beta-casein milk. It is important to note that without genetic testing, the A2 status of any individual cow's milk cannot be guaranteed, even within breeds known for A2 production.

Indian Indigenous Breeds (Desi Cows)

Many native Indian cattle breeds have a high probability of carrying the A2A2 gene. These include:

Gir: Known for high-quality milk and resilience.
Sahiwal: Considered one of the best Indian dairy breeds, known for creamy, rich milk.
Rathi: Found in Rajasthan, known for nutritious A2 milk.
Red Sindhi: A breed well-adapted to hotter climates.
Tharparkar: Another native Indian breed valued for A2 milk.

European Breeds High in A2 Genetics

While some European breeds are predominantly A1, certain breeds are known to carry a higher percentage of the A2 gene:

Guernsey: Over 90% of Guernseys carry the A2 beta-casein variant.
Jersey: Many Jersey cows produce A2 milk, with a significant portion of the breed carrying the A2A2 gene.
Brown Swiss: This breed also has a higher percentage of A2 genetics compared to some others.
Normande: Another European breed with a higher likelihood of producing A2 milk.

Identifying Genuine A2 Milk

For consumers, it is impossible to distinguish between A1 and A2 milk by taste, smell, or appearance alone. To ensure a product is genuinely A2, look for products from brands that explicitly state their milk comes from A2-tested herds. Reputable producers perform genetic testing on their cows and may offer third-party certification to guarantee their product's A2 status. Without proper testing and segregation of herds, there is a risk of cross-contamination.

A1 vs. A2 Milk: A Comparison of Protein and Digestion


Feature	A1 Milk	A2 Milk
Beta-Casein Protein	Contains A1 and A2 beta-casein proteins.	Contains only A2 beta-casein protein.
Digestion Process	A1 protein releases the BCM-7 peptide during digestion for some individuals.	A2 protein does not release the BCM-7 peptide.
Digestive Comfort	May cause digestive issues like bloating, gas, and discomfort in sensitive individuals.	Reported to be easier to digest for those sensitive to A1 protein.
Common Sources	High prevalence in European breeds like Holstein and Friesian.	Higher prevalence in indigenous Indian breeds (Gir, Sahiwal) and some European breeds (Guernsey).

Conclusion: Choosing the Right Milk for You

Determining which cow's milk is A2 milk is a matter of understanding cow genetics and careful sourcing. A2 milk is not inherently superior in nutritional content, as both A1 and A2 milk offer similar amounts of calcium, protein, and vitamins. The key difference lies in the A2 protein's potential for easier digestion for individuals with specific sensitivities to the A1 protein and its BCM-7 peptide byproduct. If you suspect that regular milk causes digestive discomfort, trying a certified A2 milk product from a breed known for A2 production, such as the Gir or Guernsey, might be worthwhile. However, A2 milk is not a fix for lactose intolerance or milk allergies, as it contains both lactose and milk proteins. Ultimately, the right choice is based on your individual body's response and dietary needs. For those interested in deeper research, studies published on the National Institutes of Health website provide further context on the A1 vs. A2 debate.

The Role of Testing and Breeding

The dairy industry produces A2 milk by testing and selectively breeding cows with the A2A2 gene. This process involves separating A2-producing cows from those that produce A1 protein to avoid cross-contamination. For consumers, this highlights the importance of choosing products from transparent companies that can provide certification of their milk's A2 status. Given that some common breeds like Jersey can produce both A1 and A2, brand transparency is more important than breed alone.

Is A2 Milk Suitable for Everyone?

While A2 milk can be a gentler option for some, it is crucial to remember its limitations. It still contains lactose, making it unsuitable for those with true lactose intolerance. Similarly, individuals with a diagnosed milk protein allergy should avoid both A1 and A2 milk, as they contain the same primary proteins. The benefits reported are primarily related to specific digestive discomfort linked to the A1 beta-casein protein, and more independent research is still needed on the broader health claims.

Frequently Asked Questions

The primary difference lies in the beta-casein protein. A2 milk contains only the A2 protein, while regular milk, or A1 milk, contains both A1 and A2 proteins due to a genetic mutation in some cows.

Breeds with a high likelihood of producing A2 milk include Indian breeds like Gir, Sahiwal, and Red Sindhi, as well as European breeds such as Guernsey, Jersey, and Brown Swiss.

Some people report that A2 milk is easier to digest because the A2 protein does not release the BCM-7 peptide during digestion, which has been linked to digestive discomfort in those sensitive to it.

No, A2 milk is not a substitute for lactose-free milk. It contains the same amount of lactose as conventional milk and will not help those with lactose intolerance.

Look for products that are explicitly labeled and certified as A2 milk. These brands typically use genetic testing on their herds to ensure the absence of A1 protein and prevent cross-contamination.

Visually and in taste, there is no significant difference between A1 and A2 milk that can be detected by consumers. Claims of a 'golden hue' in some A2 milk are due to the cow's diet, not the protein type.

No, the nutritional profile of A2 milk is very similar to regular milk of the same type (e.g., whole or fat-free), containing the same levels of protein, calcium, and vitamins.