Is A2 Protein Inflammatory? The Truth About A1 vs A2 Milk

December 24, 2025 •

3 min read

Scientific research indicates that while A1 protein in regular milk can trigger an inflammatory response in some sensitive individuals, A2 protein is generally not considered inflammatory. This distinction is rooted in a minor amino acid difference between the two beta-casein proteins.

Quick Summary

A2 protein is not inherently inflammatory, unlike the A1 protein in regular milk that releases the peptide BCM-7, linked to gut inflammation in some people.

Key Points

A1 vs. A2 Protein: The A1 beta-casein protein found in conventional milk can release an inflammatory peptide (BCM-7), while the A2 protein does not.
Digestive Discomfort: Many people who experience digestive issues like bloating and abdominal pain after drinking regular milk are reacting to A1 protein, not just lactose.
Reduced Inflammation: Studies show that consuming A2 milk is linked to fewer inflammatory markers and less gut inflammation compared to milk containing A1 protein.
Not a Cure-All: A2 milk is not a solution for a cow's milk allergy and is not lactose-free, but it can provide relief for those with A1 protein sensitivity.
Genetic Origins: The A2 protein is the original beta-casein variant and is found in milk from heritage cow breeds, goats, and sheep, which is more similar to human milk protein.
Individual Response Varies: Not everyone is sensitive to the A1 protein. For those who are, switching to A2 milk is a simple dietary change with noticeable benefits.

A1 vs. A2 Protein: The Core Difference

Historically, all cows produced milk containing only the A2 beta-casein protein. A genetic mutation introduced the A1 beta-casein protein, now common in conventional milk. The key difference lies in a single amino acid at position 67, which impacts how they are digested. The A1 protein can release beta-casomorphin-7 (BCM-7) during digestion, a peptide linked to digestive issues and inflammation in some individuals. A2 protein does not release BCM-7, making it potentially easier to digest.

The Inflammatory Role of A1 Protein and BCM-7

Studies suggest a link between A1 protein, BCM-7, and inflammation, particularly in the gut. A 2016 trial found that people drinking A1-containing milk had more gut inflammation and digestive discomfort than those drinking A2 milk. This was associated with BCM-7 from A1 beta-casein. Inflammatory markers linked to A1 protein digestion can include:

Higher fecal calprotectin.
Increased myeloperoxidase.
Changes in TNF-α and cortisol.

Digestive symptoms from A1 sensitivity can resemble lactose intolerance, such as bloating and abdominal pain. However, switching to A2 milk, which contains lactose, has helped alleviate symptoms in some cases.

Is A2 Milk Inherently Anti-Inflammatory?

While A2 protein is not considered inflammatory, some research suggests it might have anti-inflammatory effects. A review noted A2 milk consumption wasn't linked to post-dairy discomfort and could be useful for athletes with GI issues. Another study found A2 milk improved growth and reduced inflammation in stunted children. The absence of BCM-7 from A2 milk appears to be a key factor for many with dairy sensitivities.

Comparison Table: A1 vs A2 Beta-Casein


Feature	A1 Beta-Casein	A2 Beta-Casein
Genetic Origin	Result of a genetic mutation.	Original beta-casein variant.
Digestion	Can release BCM-7.	Does not release BCM-7.
Inflammatory Effect	Linked to gut inflammation in sensitive individuals.	Considered non-inflammatory.
Associated Symptoms	Bloating, pain, digestive discomfort.	Fewer digestive symptoms.
Found In	Most conventional cow's milk.	Specialty A2 milk, heritage breeds.
Research	Linked to increased inflammatory markers.	Associated with reduced inflammation in some studies.

Who Benefits from A2 Milk?

A2 milk is not necessary for everyone. It's beneficial for individuals experiencing digestive symptoms from regular milk. This includes:

Those with post-dairy digestive discomfort: A trial of A2 milk can help determine if A1 protein, not lactose, is the cause of symptoms.
Athletes: A2 milk may be easier to digest for athletes, providing nutrition without the GI issues sometimes caused by regular milk.
People with mild inflammatory gut issues: Removing A1 protein might provide relief for those with mild gut inflammation.

Conclusion

A2 protein itself is not inflammatory, but the A1 protein in most milk can be. The difference lies in digestion and the potential release of BCM-7. For many with digestive sensitivities, switching to A2 milk can reduce discomfort and inflammatory markers. While more research is ongoing, evidence suggests A2 milk is a gentler dairy option for a significant population segment.

For more details on a specific randomized clinical trial discussing the difference between A1 and A2 milk, you can review this article: {Link: NCBI https://pmc.ncbi.nlm.nih.gov/articles/PMC4818854/}.

Frequently Asked Questions

The difference is a single amino acid at position 67 of the beta-casein protein chain. In A1 protein, it's histidine, which allows the release of the inflammatory peptide BCM-7. In A2 protein, it's proline, which prevents this release during digestion.

When the A1 beta-casein protein is digested, it can release the bioactive peptide beta-casomorphin-7 (BCM-7). This peptide has been linked in studies to increased gastrointestinal inflammation and discomfort in susceptible individuals.

A2 milk is not lactose-free, so it won't resolve issues for people with true lactose intolerance. However, many who believe they are lactose intolerant may actually be sensitive to the A1 protein, and in these cases, A2 milk can be tolerated with fewer symptoms.

Symptoms of A1 protein sensitivity can mimic lactose intolerance and include bloating, gas, abdominal pain, and digestive discomfort. These issues are often due to the inflammatory response triggered by the BCM-7 peptide.

Yes, for individuals sensitive to the A1 protein, switching to A2 milk can support better gut health by reducing inflammation. It avoids the release of BCM-7, which can irritate the digestive tract.

A2 milk comes from cow breeds that have not undergone the genetic mutation that created the A1 protein. These include heritage breeds like Guernsey and Jersey, as well as milk from goats and sheep, which are naturally A2.

For those with A1 protein sensitivity, A2 milk is proven to be easier to digest and less likely to cause inflammatory responses. However, for those without this sensitivity, the health benefits are largely the same, and more research is ongoing.