Nutrition Diet: What is better for you, A1 or A2 milk?

October 28, 2025 •

3 min read

The difference between A1 and A2 milk lies in a single amino acid at position 67 of the beta-casein protein chain. For some individuals, this minor variation is the key to understanding why they experience digestive discomfort from regular milk, raising the question: What is better for you, A1 or A2 milk?

Quick Summary

A1 and A2 milk differ in their beta-casein protein, with A1 potentially producing a peptide called BCM-7 linked to digestive discomfort in sensitive individuals. While A2 milk is easier to digest for some, current research lacks strong evidence that it is superior for the general population. The best choice is often a matter of individual tolerance.

Key Points

Protein Difference: A1 and A2 milk differ by a single amino acid in their beta-casein protein chain, which affects digestion.
Digestive Comfort: For some people with milk sensitivity, A2 milk is easier to digest because it doesn't release the peptide BCM-7, which is linked to discomfort from A1 milk.
Not Lactose-Free: A2 milk still contains lactose. People with medically diagnosed lactose intolerance should seek lactose-free options, not simply switch to A2 milk.
Controversial Health Claims: Evidence linking A1 milk to broader health issues like type 1 diabetes and heart disease is inconclusive and often based on observational studies.
Individual Test: The best way to know which is better for you is to try A2 milk and monitor your body's response, especially if you experience mild digestive upset with regular milk.
Nutritionally Similar: Aside from the beta-casein variant, the overall nutritional content (protein, vitamins, minerals) is comparable in A1 and A2 milk.
Market Factors: A2 milk is typically more expensive and may be less widely available than conventional A1/A2 milk.

Most cow's milk contains a mix of two types of beta-casein protein, A1 and A2. A decade-long discussion exists regarding the potential health differences between milk with both proteins and milk containing only the A2 type, focusing on digestion and gut health. For some, this difference may alleviate symptoms previously linked to lactose intolerance or general dairy sensitivity.

Understanding the Beta-Casein Difference

Beta-casein is a significant protein in milk, making up about 30% of the total. While A1 and A2 milk have similar nutritional profiles, a genetic difference influences how these proteins are digested.

What is A1 Milk?

A1 milk comes primarily from breeds like Holstein and Friesian. The A1 beta-casein has a histidine at position 67 in its protein chain, which facilitates the release of beta-casomorphin-7 (BCM-7) during digestion.

What is A2 Milk?

Cows historically produced only A2 beta-casein. A2 milk comes from breeds like Jersey and Guernsey, or specifically selected cows. The A2 protein has proline at position 67, preventing BCM-7 formation in the same way as A1, leading to claims that it's gentler on digestion.

Digestion and the Role of BCM-7

The impact of BCM-7 on digestion is central to the A1/A2 discussion. In sensitive individuals, this peptide can cause various gastrointestinal issues, including slower digestion, increased gut inflammation, and discomfort such as bloating, gas, and pain.

Lactose Intolerance vs. Protein Sensitivity

It's crucial to distinguish A1 protein sensitivity from lactose intolerance. A2 milk contains lactose. Some people who believe they are lactose intolerant may actually be reacting to the A1 protein and find relief with A2 milk. A2 milk won't help those with medically diagnosed lactose intolerance unless it's also lactose-free.

A1 vs. A2 Milk: A Comparative Look


Feature	A1 Milk	A2 Milk
Beta-Casein Protein	Contains A1 and A2 types	Contains only A2 type
Associated Peptide	Releases beta-casomorphin-7 (BCM-7) during digestion	Does not release BCM-7 in significant amounts
Source Cows	Primarily Northern European breeds like Holstein and Friesian	Specific breeds like Jersey, Guernsey, and certain indigenous cows
Digestive Effects	Linked to discomfort such as bloating, gas, and inflammation in sensitive individuals	Reported to be easier to digest for those with milk sensitivities
Overall Nutrition	Nutritionally similar to A2 milk	Nutritionally similar to A1 milk
Cost and Availability	More widely available and often less expensive	Can be more expensive and less readily available

Navigating the Science on A1 and A2 Milk

The scientific perspective on the A1/A2 difference varies. Some studies support digestive benefits for A2 milk, while others call for more conclusive evidence.

Support for Digestive Benefits

Studies have indicated improved digestive outcomes with A2 milk in individuals reporting milk sensitivities. For example, studies in Chinese adults and preschoolers with reported milk sensitivities showed less digestive discomfort and inflammation with A2 milk compared to A1/A2 milk.

Other Health Claims and Conflicting Evidence

Claims linking A1 milk to serious conditions like type 1 diabetes, heart disease, and autism are controversial. The evidence is often observational and less robust, showing association rather than causation. Regulatory bodies like EFSA have found no established cause-and-effect relationship between BCM-7 and these diseases based on current research. Some research even suggests A1 milk may empty faster from the stomach, potentially increasing symptoms. Experts generally agree more long-term human studies are needed.

Making the Right Choice for Your Health

The decision of what is better for you, A1 or A2 milk, is personal. For those without digestive issues, both are nutritionally similar, and the choice may come down to price and availability. If you have digestive discomfort from regular milk but aren't lactose intolerant, trying A2 milk is a good option. Since relief is linked to protein sensitivity, not lactose, A2 milk might allow you to enjoy dairy without discomfort. Trying A2 milk and observing your symptoms is the best approach. Brands like The A2 Milk Company specialize in A1-protein-free milk. Ultimately, the choice depends on your personal experience and tolerance. Consult a healthcare provider or dietitian for significant dietary changes, especially with existing health conditions.

Conclusion

The A1 vs. A2 milk discussion highlights a protein difference impacting digestion for some. A1 milk can cause discomfort in sensitive individuals due to BCM-7, while A2 milk is often better tolerated. Claims about A1 milk causing severe diseases lack strong scientific support. For those with milk sensitivity but not lactose intolerance, A2 milk might be a solution. Otherwise, both milk types provide similar nutrition, making the choice a personal one based on individual response.

Frequently Asked Questions

The main difference lies in the beta-casein protein. Standard A1 milk contains both A1 and A2 beta-casein, while A2 milk contains only the A2 beta-casein protein. This variation is due to a single amino acid difference in the protein structure.

For some individuals who experience digestive issues with regular milk but are not lactose intolerant, A2 milk may be easier to digest. This is because the A1 protein can release a peptide (BCM-7) during digestion that is linked to gastrointestinal discomfort in sensitive people.

No, A2 milk still contains lactose, the sugar found in milk. People with lactose intolerance who cannot digest this sugar will not find relief by switching to A2 milk alone, unless they purchase a specific lactose-free A2 product.

Some claims have been made regarding A2 milk and reduced risk for other conditions like type 1 diabetes and heart disease, but the scientific evidence for these links is not conclusive. The strongest evidence for a difference between A1 and A2 milk relates to digestive comfort.

No, both A1 and A2 milk have a very similar nutritional profile, containing the same essential vitamins and minerals like calcium, protein, and potassium. The primary difference is how the beta-casein protein is digested by sensitive individuals.

A2 milk is typically more expensive due to the specialized sourcing and production processes involved. Dairy farms must genetically test their cows to ensure they only produce the A2 protein, and this milk must be processed separately to prevent cross-contamination.

The best way is to try it for yourself. If you experience mild digestive discomfort after consuming regular cow's milk, switch to A2 milk for a few weeks and observe if your symptoms improve. There is no universal answer, as the effects vary based on individual sensitivity to the A1 protein.