What is the Difference Between A1 and A2 Milk?
Beta-casein, making up about 30% of cow's milk protein, is the subject of the A1 and A2 milk distinction. The ancestral form, A2, is common in many mammals. The A1 variant arose from a genetic mutation in some European cattle. The key difference lies in the amino acid at position 67: A2 has proline, while A1 has histidine. This structural difference means A1 protein releases the peptide beta-casomorphin-7 (BCM-7) during digestion, while A2 protein does not.
The Composition of UK Milk
Due to prevalent high-yielding breeds in the UK like Holstein-Friesian, standard supermarket milk is a mix of A1 and A2 beta-casein. Research confirms this blend, with a significant presence of both variants in retail milk. This means conventional UK milk is a combination product reflecting the national dairy herd's genetics.
The Digestive Implications of A1 vs. A2
Interest in A2 milk often comes from suggestions it's easier to digest for some people. The BCM-7 peptide from A1 protein has been linked to digestive issues like bloating and gas in sensitive individuals. These protein-related symptoms are distinct from lactose intolerance, though sometimes confused. While A2 milk contains lactose, some report improved digestion after switching from standard milk. A2 milk is not suitable for those with diagnosed milk allergy or lactose intolerance.
Potential Health Link Controversies Some early claims linked BCM-7 to serious conditions like type 1 diabetes and heart disease. However, reviews by authorities like the European Food Safety Authority (EFSA) have found no established causal link between BCM-7 and these non-communicable diseases. Claims about digestive comfort have more research support, but links to more serious health issues remain scientifically debated and largely unsubstantiated.
How is Pure A2 Milk Produced and Sourced in the UK?
Producing A2-only milk requires specific practices:
- Genetic Testing: Cows are tested to determine if they have the A2/A2 genotype, meaning they produce only A2 protein.
- Selective Breeding: Only A2/A2 cows are used for A2 milk production, with breeding programs maintaining A2-only herds.
- Herd Segregation: A2 cows are kept and milked separately to avoid mixing with milk from cows producing A1.
- Batch Testing: The milk is tested again during processing to confirm its A2 protein content.
Although the a2 Milk Company is no longer in the UK market, independent dairy farms still produce and sell pure A2 milk. These farms often favor breeds known for higher A2 prevalence, such as Jersey and Guernsey, and use selective breeding.
Comparison Table: A1 vs. A2 Milk
| Feature | A1 Milk (Regular UK Milk) | A2 Milk (Specialty UK Milk) |
|---|---|---|
| Beta-Casein Protein | Contains a mix of A1 and A2 variants | Contains only the A2 variant |
| Amino Acid at Position 67 | Histidine | Proline |
| BCM-7 Release During Digestion | Releases BCM-7, a peptide that may cause digestive issues | Minimizes or prevents BCM-7 release |
| Associated Digestive Issues | Linked to bloating, gas, and discomfort in sensitive individuals | Considered easier to digest for some people |
| Health Controversy | Early links to other diseases remain unsubstantiated by major bodies | Not associated with the same health controversies as A1 |
| Taste and Appearance | Indistinguishable from A2 milk in taste and appearance | Indistinguishable from A1 milk in taste and appearance |
| Source Breeds | Primarily from Northern European breeds like Holstein-Friesian | From specifically tested and bred A2 herds, often Jersey or Guernsey |
| Availability in UK | Widespread in all major supermarkets and retailers | Less common; found at specialized dairies and independent stores |
Conclusion
Milk in the UK is typically a blend of both A1 and A2 beta-casein proteins due to the genetics of common dairy breeds. The main difference lies in how they are digested; A1 releases BCM-7, a peptide linked to digestive discomfort for some. While broader health claims about A1 lack strong evidence, A2 milk might help alleviate gastrointestinal symptoms for sensitive individuals. In the UK, consumers can find A2-only milk from independent farmers and specialty brands, often from breeds like Jersey or Guernsey. Understanding this distinction helps in making informed choices, especially for managing dairy-related digestive issues.
For Further Information
To learn more about the complexities of beta-casein variants and milk composition, consult scientific literature, such as research published in the journal Foods.
Summary of A1 vs. A2 Milk in the UK
- Standard UK Milk is a Blend: Most retail milk in the UK contains a mix of both A1 and A2 beta-casein proteins.
- The Protein Difference is Minor but Key: A single amino acid change causes A1 protein to release BCM-7 during digestion, unlike A2 protein.
- BCM-7 Can Cause Discomfort: The peptide BCM-7 is thought to cause digestive symptoms like bloating in some sensitive people.
- A2 Milk is Specifically Sourced: Pure A2 milk comes from genetically tested and selectively bred A2-only herds.
- Availability is Specialized: Pure A2 milk is available in the UK from specialist farms and independent dairies, not typically in large supermarkets.
