Nutrition Diet: What milk has only A2? A comprehensive guide to beta-casein protein

October 28, 2025 •

4 min read

Originally, all cow's milk contained only the A2 beta-casein protein before a genetic mutation in European cattle introduced the A1 variant. Many are now asking what milk has only A2, focusing on this protein difference for improved digestive comfort.

Quick Summary

A2 milk contains only the A2 beta-casein protein, unlike regular milk with both A1 and A2. It comes from specific cow breeds and may offer easier digestion for some sensitive individuals, though it is not a solution for lactose intolerance.

Key Points

A1 vs. A2 Protein: The difference in milk is due to a single amino acid variation in the beta-casein protein.
Sources of A2 Milk: Milk from certain cow breeds like Jersey, Guernsey, and Gir, as well as most non-cow dairy (goat, sheep, buffalo), naturally contains only A2 protein.
Digestive Benefits: A2 milk may be easier to digest for some people who experience discomfort from the BCM-7 peptide produced by A1 protein.
A2 vs. Lactose Intolerance: A2 milk contains lactose and is not a cure for lactose intolerance, though it can help those with A1 protein sensitivity.
Certified A2 Milk: Brands verify A2-only milk by genetically testing their herds and keeping their milk supply separate from conventional dairy.
Nutritional Value: The nutritional profile of A2 milk is very similar to that of regular milk, providing the same essential vitamins and minerals.

The Science Behind A1 and A2 Milk

To understand what milk has only A2, it is essential to first know the difference between A1 and A2 beta-casein proteins. Beta-casein is the second most common protein found in milk, making up about 30% of its total protein content. The distinction between the A1 and A2 variants is based on a single amino acid at position 67 in their protein chain.

In A1 beta-casein, a histidine amino acid is present at this position. During digestion, this histidine can cause the release of a peptide called beta-casomorphin-7 (BCM-7). Research suggests that for some people, this BCM-7 peptide can lead to digestive discomfort, including bloating and gas, and has been linked to changes in bowel function.

In contrast, A2 beta-casein has a proline amino acid at the same position. This structural difference means that A2 milk does not produce the same level of BCM-7 during digestion, which may make it easier for some individuals to digest.

What Milk Has Only A2? The Sources

Producers can market milk as 'A2-only' by ensuring it comes from cows with the specific A2/A2 genetic marker. This is achieved through DNA testing of herds and breeding practices.

Specific Cow Breeds Known for A2

Certain breeds of dairy cattle have a higher percentage of the A2 gene compared to others. These include:

Jersey: A breed known for high butterfat content, Jersey cows have a naturally high prevalence of the A2 gene.
Guernsey: Originating from the Channel Islands, Guernsey cattle are another ancient breed predominantly producing A2 milk.
Brown Swiss: This hardy breed also has a high percentage of the A2 gene.
Indigenous Indian Breeds: Breeds like Gir, Sahiwal, and Red Sindhi are well-known for their natural A2 protein production.

Conversely, most of the milk from modern commercial dairy breeds, such as Holsteins and Friesians, contains a mix of both A1 and A2 protein due to the genetic mutation mentioned earlier.

Non-Cow Dairy and Certified Brands

For those seeking milk with only A2 protein, there are two primary options:

Non-Cow Dairy: Milk from other mammals, such as goats, sheep, buffalos, and camels, naturally contains predominantly A2 beta-casein, making them a default A2-only option.
Certified Cow's Milk Brands: Companies like The a2 Milk Company and Alexandre Family Farm genetically test their herds to ensure the milk they produce is A2-only. They keep these herds and their milk separated to prevent cross-contamination.

Potential Benefits and Considerations for Your Nutrition Diet

For some people with sensitivities to the A1 beta-casein, switching to A2 milk can lead to a reduction in digestive issues like bloating and discomfort. It is important to note that A2 milk is not a solution for true lactose intolerance, as it contains the same amount of lactose as regular milk. A healthcare provider can help determine if the issue is a casein sensitivity rather than lactose intolerance.

From a nutritional standpoint, the content of calcium, vitamin D, and other essential nutrients is nearly identical between A1 and A2 milk. Therefore, the primary consideration for choosing A2 milk is digestive comfort, not superior nutritional content.

Comparing A1 and A2 Milk


Characteristic	A1 Milk	A2 Milk
Beta-Casein Protein	Contains a mix of A1 and A2 proteins.	Contains only the A2 protein.
Digestion	Can produce BCM-7 peptide, which may cause digestive issues in some people.	Produces little to no BCM-7, potentially easier to digest.
Common Cow Breeds	Holsteins, Friesians, Ayrshires.	Jerseys, Guernseys, Brown Swiss, indigenous Indian breeds.
Typical Sources	Most conventional cow's milk on the market.	Non-cow dairy, genetically tested herds, certified A2 brands.
Nutritional Value	Similar to A2 milk, rich in calcium and vitamins.	Similar to A1 milk, rich in calcium and vitamins.

Making A2 Milk Part of Your Nutrition Diet

Finding milk with only A2 protein requires checking labels and, in the case of cow's milk, relying on certified brands. For non-cow dairy, most is naturally A2-only. Here is a list of sources for milk with only A2 protein:

Goat's Milk: Readily available and naturally contains predominantly A2 beta-casein.
Sheep's Milk: Also a great source of A2 protein, often available from specialty producers.
Buffalo's Milk: In many parts of the world, buffalo milk is consumed for its creamy taste and A2 protein composition.
The a2 Milk Company: This brand offers genetically tested cow's milk with guaranteed A2-only protein.
Alexandre Family Farm: Provides organic A2/A2 cow's milk from a genetically tested herd.

Conclusion

Ultimately, understanding what milk has only A2 is a personal choice based on how your body digests dairy proteins. While regular milk from conventional cow breeds contains a mix of A1 and A2 proteins, milk from specific ancient cow breeds and most non-cow dairy is predominantly A2-only. For those who experience digestive discomfort with standard dairy, exploring A2 milk from certified brands or non-cow sources may provide relief. However, consulting a healthcare professional is always recommended to identify the root cause of digestive issues. For more in-depth scientific literature on milk proteins, consider researching academic databases like the National Library of Medicine.

Frequently Asked Questions

No, A2 milk is not lactose-free. It contains the same amount of lactose as regular milk, so it will not help with lactose intolerance.

You cannot determine if milk is A1 or A2 by taste, smell, or sight. The only way to know for sure is to purchase from a brand that certifies its products through genetic testing of their cows.

BCM-7 is a peptide released when the A1 beta-casein protein is digested. A2 milk produces little to no BCM-7, which may be why some people find it easier on their digestive system.

No. While all cows produce some A2 protein, most conventional breeds like Holsteins produce a mix of A1 and A2. Only cows with the A2/A2 gene produce exclusively A2 milk.

Milk from most non-bovine mammals, including goats, sheep, buffalos, and camels, is predominantly or exclusively A2 milk.

The nutritional value of A2 milk, including its calcium, vitamin D, and protein content, is very similar to regular milk. The main difference lies in potential digestive comfort for some individuals.

No. An allergy to milk protein is different from a sensitivity to the A1 beta-casein. A2 milk still contains milk protein and would not be suitable for someone with a milk protein allergy.