Can A2 milk upset your stomach?: Decoding the Digestive Differences

October 17, 2025 •

2 min read

According to research, many people experience digestive discomfort after consuming regular milk, leading to the rise of alternatives like A2 milk. This article explores the science behind the A1 and A2 milk protein variations and addresses the question: can A2 milk upset your stomach?.

Quick Summary

A2 milk contains only the A2 beta-casein protein, which can be easier to digest for some people with milk sensitivities, unlike regular milk containing both A1 and A2 proteins. However, it is not suitable for individuals with a true milk allergy or lactose intolerance, who may still experience digestive issues.

Key Points

A1 vs. A2 Protein: Regular milk contains both A1 and A2 beta-casein proteins, while A2 milk contains only the A2 type.
BCM-7 Peptide: The A1 protein can release a peptide called BCM-7 during digestion, which is linked to digestive discomfort similar to lactose intolerance.
Not Lactose-Free: A2 milk contains the same amount of lactose as regular milk and is not suitable for those with diagnosed lactose intolerance.
Not Allergy-Safe: A2 milk is not a safe alternative for individuals with a cow's milk protein allergy, as they will react to all milk proteins, including A2.
Reduced Symptoms: Many people with A1 protein sensitivity report reduced bloating, gas, and abdominal discomfort when they switch to A2 milk.
Seek Diagnosis: It is crucial to consult a healthcare professional to distinguish between lactose intolerance, A1 sensitivity, and a milk protein allergy.
Alternative A2 Sources: Goat, sheep, and buffalo milk naturally contain A2 beta-casein protein.

Understanding the Milk Proteins: A1 vs. A2

Regular milk typically contains both A1 and A2 beta-casein proteins, while A2 milk comes from cows that produce only the A2 protein. The A1 protein, when digested, releases a peptide called beta-casomorphin-7 (BCM-7), which has been linked to digestive discomfort. A2 protein does not release significant amounts of BCM-7, which is why it is often considered easier to digest for some individuals.

Why A2 milk might still cause digestive issues

A2 milk is not a universal solution for all dairy digestive problems. It contains the same amount of lactose as regular milk, making it unsuitable for individuals with lactose intolerance. For those with a true cow's milk protein allergy, A2 milk is also not safe as it still contains milk proteins that trigger an immune response.

Potential benefits for A1-sensitive individuals

For those specifically sensitive to the A1 protein, switching to A2 milk may offer benefits based on research and anecdotal evidence. Studies suggest A2 milk may improve gut motility, reduce inflammation, support a healthier gut microbiome, and lessen gastrointestinal symptoms by avoiding the BCM-7 peptide.

A1 vs. A2 Milk Comparison Table


Feature	A1 Milk (Conventional Milk)	A2 Milk	Remarks
Beta-Casein Protein	Contains a mix of A1 and A2.	Contains only A2.	Difference is a single amino acid.
BCM-7 Release	Releases significant BCM-7 during digestion.	Releases little to no BCM-7.	BCM-7 linked to discomfort.
Potential Digestive Impact	May cause discomfort in A1-sensitive individuals.	Associated with fewer issues for A1-sensitive individuals.	Not a universal solution.
Suitability for Lactose Intolerance	Unsuitable (contains lactose).	Unsuitable (contains lactose).	Lactose-free A2 options exist.
Suitability for Cow's Milk Allergy	Unsuitable (contains milk proteins).	Unsuitable (contains milk proteins).	Requires complete avoidance of cow's milk proteins.

The importance of proper diagnosis

Identifying the specific cause of milk-related digestive issues is crucial, as symptoms of lactose intolerance and A1 casein sensitivity can overlap. Consulting a healthcare professional or registered dietitian is recommended to determine the root cause and guide dietary choices.

The path forward for better gut health

For those sensitive to the A1 protein, A2 milk may help manage symptoms while providing essential nutrients. Other dairy options naturally higher in A2 protein include goat's, sheep's, and buffalo milk. Understanding individual responses to milk proteins is key to managing digestive health, and A2 milk is a potential option for A1-sensitive individuals as part of a personalized dietary plan. For more information on beta-casein variants, refer to scientific studies available through resources like the NIH.

Conclusion

A2 milk may alleviate digestive symptoms for individuals sensitive to the A1 protein by avoiding the release of BCM-7. However, it will still cause discomfort for those with lactose intolerance or a cow's milk protein allergy. A proper diagnosis is essential to determine if A2 milk is a suitable option for managing digestive issues.

Frequently Asked Questions

The primary difference lies in the type of beta-casein protein they contain. Regular milk typically has both A1 and A2 beta-casein, while A2 milk comes from cows that naturally produce only the A2 variant.

No, A2 milk is not suitable for people with lactose intolerance. It contains the same amount of lactose as regular milk, so it will likely cause the same symptoms of bloating and gas.

No, A2 milk is not a solution for a true cow's milk protein allergy. A milk allergy is an immune response to milk proteins, and individuals with this condition will react to both A1 and A2 protein variants.

For some individuals, A2 milk is easier to digest because the A2 beta-casein protein does not release the peptide BCM-7 in the same way the A1 protein does. BCM-7 has been linked to increased inflammation and digestive discomfort.

A1 beta-casein can cause digestive symptoms such as gas, bloating, abdominal pain, diarrhea, and constipation, especially in those with a sensitivity.

It is best to consult a healthcare provider for an accurate diagnosis. Symptoms can overlap, and the root cause can only be identified through proper testing and medical evaluation.

Yes, milk from other animals like goats, sheep, and buffalo is naturally higher in the A2 beta-casein protein. Some people find they can tolerate these dairy products better than conventional cow's milk.