What Does A2 Milk Contain? The Key Protein and Nutrient Profile

December 18, 2025 •

3 min read

Historically, all cow's milk naturally contained only the A2 beta-casein protein, but a genetic mutation led to the presence of A1 protein in modern herds. This difference is the key to understanding what does A2 milk contain, and why it is marketed for potential digestive benefits.

Quick Summary

A2 milk contains only the A2 beta-casein protein, unlike regular cow's milk which includes both A1 and A2 variants. It is nutritionally similar but is potentially easier to digest for some individuals due to the absence of the A1 protein variant.

Key Points

A2 Beta-Casein Only: A2 milk comes from cows producing only the A2 beta-casein protein, differing from regular milk.
No A1 Beta-Casein: It lacks the A1 protein, which may release the BCM-7 peptide during digestion and cause discomfort.
Potential Digestive Ease: Some individuals find A2 milk easier to digest, potentially due to the absence of A1 protein.
Same Foundational Nutrients: Nutritionally, A2 milk is comparable to regular milk, providing protein, calcium, vitamins, and minerals.
Contains Lactose: A2 milk is not suitable for lactose intolerant individuals as it contains lactose.
Not for Milk Allergy: It is not an alternative for those with a cow's milk protein allergy.
Source Matters: A2 milk is sourced from specific cows identified through genetic testing.

A2 milk is a type of cow's milk distinguished by its protein composition. While its appearance, taste, and nutritional value are similar to regular milk, its key difference lies in the specific beta-casein protein it contains. This has led some consumers to choose A2 milk, believing it may help reduce digestive discomfort. To understand what A2 milk contains, it's crucial to look at its protein content and how it compares to standard milk.

The Unique Protein: A2 Beta-Casein

Beta-casein is a major protein in milk, making up about 30% of the total protein. Standard milk from many Western dairy cows contains both A1 and A2 beta-casein proteins. A2 milk, however, comes from specially selected cows and contains only the A2 protein.

The difference between the A1 and A2 proteins is a single amino acid at position 67 in their chain. A2 protein has proline there, while A1 has histidine. This small difference affects how the protein is digested. When A1 protein breaks down, it can release beta-casomorphin-7 (BCM-7). Some research suggests BCM-7 might slow digestion and contribute to issues like bloating and gas in some people. The structure of A2 protein prevents BCM-7 release, which is why it's thought to be easier to digest.

Beyond Beta-Casein: The Full Nutritional Profile

Beyond the specific beta-casein, what does A2 milk contain nutritionally? It offers a comprehensive set of nutrients similar to regular milk.

Key Nutrients Found in A2 Milk

High-quality protein: Provides about 8 grams per cup, important for muscles.
Calcium: Essential for strong bones and teeth.
Vitamin D: Helps calcium absorption and supports immunity.
Vitamins A and B12: Important for vision, immune health, and brain function.
Potassium: An electrolyte that helps manage blood pressure.
Fats: Content varies by type (whole, 2%, etc.) and includes omega-3s.
Lactose: Contains lactose, making it unsuitable for those with lactose intolerance.

A2 Milk vs. Regular Milk: A Comparative Look


Feature	A2 Milk	Regular (A1/A2) Milk
Beta-Casein Protein	Contains only the A2 variant.	Contains both A1 and A2 variants.
BCM-7 Peptide	Does not release BCM-7 during digestion.	May release BCM-7, which can be linked to digestive issues.
Digestive Impact	May be easier to digest for some individuals sensitive to the A1 protein.	May cause digestive discomfort like bloating, gas, and stomach cramps in sensitive people.
Lactose Content	Contains lactose; not suitable for those with lactose intolerance.	Contains lactose; not suitable for those with lactose intolerance.
Nutritional Profile	Very similar to regular milk in terms of calories, protein, fat, vitamins, and minerals.	Very similar to A2 milk in terms of calories, protein, fat, vitamins, and minerals.

Addressing Misconceptions and Benefits

It's important to note that A2 milk's potential benefits primarily apply to individuals sensitive to the A1 beta-casein protein, not those with lactose intolerance or a milk protein allergy. For those with lactose intolerance or a true milk allergy, A2 milk is not a suitable alternative.

The main benefit reported for A2 milk is potential ease of digestion for sensitive individuals. By excluding the A1 protein, some people find they can consume cow's milk without the digestive discomfort they previously experienced. However, ongoing research is needed to fully understand and confirm all potential health claims related to A2 milk.

Conclusion: Choosing What's Right for Your Body

In conclusion, what does A2 milk contain? It contains the same essential nutrients as regular milk but with a crucial difference in the beta-casein protein: it has only the A2 variant and lacks the A1 variant. For some individuals, this absence of the A1 protein can lead to reduced digestive discomfort, making A2 milk a preferred choice. It does not address lactose intolerance or milk allergies. Ultimately, the best milk option depends on individual digestive response and needs. Paying attention to how different types of milk affect your body is key. For further scientific reading, you can refer to resources like Milk proteins and human health: A1/A2 milk hypothesis - PMC.

Frequently Asked Questions

The main difference is the type of beta-casein protein; A2 milk contains only the A2 variant, while regular milk contains both A1 and A2 proteins.

From a basic nutritional standpoint, A2 milk is not superior to regular milk. It contains the same vitamins, minerals, fat, and lactose. The potential benefit lies in its different protein structure, which may be easier for some people to digest.

No, A2 milk is not lactose-free and is not suitable for individuals with a diagnosed lactose intolerance. Lactose-free versions of A2 milk are available for those who are sensitive to both lactose and A1 protein.

A2 milk is sourced from cows that have been genetically tested and selected to produce only the A2 type of beta-casein protein. Their milk is then collected and processed separately from regular milk.

No, A2 milk is not safe for individuals with a genuine cow's milk protein allergy. It still contains all the necessary milk proteins that can trigger an allergic reaction.

BCM-7 is a peptide that is released during the digestion of the A1 beta-casein protein found in regular milk. The A2 protein structure prevents the release of BCM-7, which is why A2 milk is considered easier on the stomach for some.

If you experience digestive discomfort like bloating, gas, or cramps after drinking regular milk, but have tested negative for lactose intolerance or milk allergy, you may be sensitive to the A1 protein. Switching to A2 milk can be a way to test this sensitivity.