How Do You Know If You Need A2 Milk?

December 26, 2025 •

4 min read

Approximately 65% of the adult population experiences some form of digestive discomfort after consuming dairy, but it may not always be lactose intolerance. For some, the culprit is the A1 beta-casein protein found in conventional milk.

Quick Summary

Some individuals with milk-related digestive discomfort may benefit from switching to A2 milk. These symptoms can be caused by the A1 beta-casein protein, not lactose intolerance.

Key Points

Identify the Signs: Symptoms like bloating, gas, and stomach pain after drinking regular milk, even without lactose intolerance, may indicate a sensitivity to A1 protein.
Understand the Protein Difference: The A1 beta-casein protein, found in most conventional milk, releases the peptide BCM-7 during digestion, which can trigger digestive issues in some people.
A2 Milk is Easier to Digest: A2 milk contains only the A2 beta-casein protein, which does not release BCM-7 during digestion, making it gentler on the stomach for those sensitive to A1.
Conduct a Personal Experiment: To know if you need A2 milk, try a two-week dairy elimination and then reintroduce A2 milk to see if symptoms improve. Compare your reaction to regular milk if necessary.
A2 Milk is Not Lactose-Free: If you have diagnosed lactose intolerance, A2 milk is not a solution as it still contains lactose. It addresses protein, not sugar, sensitivity.
Consult a Doctor for Allergies: Individuals with a confirmed milk protein allergy should avoid A2 milk and all other cow's milk products.
Consider the Cow's Breed: A2 milk comes from specific cow breeds like Guernsey and Jersey, while conventional milk often comes from breeds like Holstein and Friesian that produce both A1 and A2 protein.

Is It the Protein or the Sugar? Understanding Your Dairy Discomfort

When digestive troubles arise after consuming dairy, most people immediately suspect lactose intolerance, the body's inability to digest milk sugar. However, a growing body of research suggests that the problem for many is not the sugar (lactose) but the type of protein in the milk. A2 milk is a type of cow's milk that contains only the A2 beta-casein protein, while conventional milk contains a mixture of both A1 and A2 beta-casein proteins. The way these two protein types are digested can significantly differ, causing noticeable symptoms in sensitive individuals.

Signs That You Might Need A2 Milk

If you have been diagnosed with lactose intolerance, A2 milk will not solve your issues, as it still contains lactose. However, if your doctor has ruled out lactose intolerance and you still experience discomfort, an A1 protein sensitivity could be the cause.

Symptoms of A1 Beta-Casein Sensitivity

Bloating and Gas: Feelings of fullness, swelling in the abdomen, and increased flatulence after drinking milk are common signs.
Abdominal Pain: Discomfort or cramping in the stomach following milk consumption.
Altered Bowel Habits: Changes in stool consistency, with some studies noting softer stools associated with A1 protein intake.
Lactose-Like Symptoms: The symptoms triggered by A1 protein can closely mimic those of lactose intolerance, which is why it is so often misdiagnosed.
Digestive Inflammation: Some research links the digestion of A1 protein to increased inflammatory markers in the gut.

The Fundamental Difference Between A1 and A2 Proteins

The distinction between A1 and A2 milk traces back to a genetic mutation in dairy cows that occurred thousands of years ago. This mutation caused a change in the beta-casein protein, with a single amino acid difference. In the A2 protein, the 67th amino acid is proline. In the A1 protein, this amino acid is histidine.

When the A1 protein is digested, the histidine at position 67 allows for the release of a peptide called beta-casomorphin-7 (BCM-7). Research suggests that this peptide is responsible for the negative digestive symptoms in sensitive individuals. The proline in the A2 protein, however, prevents the release of BCM-7, meaning A2 milk can be digested without releasing this troublesome peptide.


Feature	A1 Milk (Conventional)	A2 Milk
Beta-Casein Protein	Contains a mix of A1 and A2	Contains only A2
BCM-7 Release	Releases BCM-7 during digestion	Does not release significant BCM-7
Digestibility	May be difficult to digest for some	Often easier to digest for sensitive individuals
Common Cow Breeds	Holstein, Friesian, Ayrshire	Guernsey, Jersey, Channel Island breeds, Zebu
Potential Side Effects	Bloating, gas, pain, inflammation	Typically fewer or no digestive issues for A1-sensitive individuals

How to Determine Your Sensitivity

Since A1 sensitivity is not a formal diagnosis with a definitive test for humans, determining if you need A2 milk involves a simple dietary experiment.

The A2 Milk Challenge

Elimination Phase: Remove all dairy products from your diet for two weeks. This allows your system to clear out any potential triggers.
A2 Reintroduction: Begin consuming A2 milk as your sole dairy source. Pay close attention to your symptoms over the next two weeks. For many, this is enough to experience relief from discomfort.
A1 Reintroduction: If you saw an improvement with A2 milk, try reintroducing conventional milk (containing both A1 and A2) to see if symptoms return. The reappearance of digestive issues confirms that the A1 protein was likely the problem.

This method allows you to be your own scientist and observe your body's specific reaction to the different protein types, giving you a conclusive answer tailored to your needs.

Conclusion: A Simple Switch for Better Digestion

For those who experience digestive distress after consuming conventional dairy, the solution may be simpler than a complex diagnosis. If you have ruled out true lactose intolerance with a medical professional, trying A2 milk is a simple and low-risk step to take. By understanding the difference between the A1 and A2 beta-casein proteins and the peptide BCM-7, you can make an informed choice that could significantly improve your digestive comfort and allow you to enjoy milk again.

For more clinical context on the subject, you can review published research from the National Institutes of Health.(https://pmc.ncbi.nlm.nih.gov/articles/PMC9407547/)

Is it a good choice for everyone? The Bigger Picture

While A2 milk can be a game-changer for those with A1 protein sensitivity, it is essential to remember that it is not a cure-all for all dairy-related issues. It still contains lactose, and individuals with a medically diagnosed cow's milk protein allergy must avoid all cow's milk products, including A2 milk. For everyone else, however, exploring A2 milk offers a viable path to better digestive health without giving up dairy entirely.

This article is for informational purposes only and does not constitute medical advice. Consult with a healthcare professional before making any dietary changes.

Frequently Asked Questions

The key difference is the beta-casein protein. A1 milk contains both A1 and A2 beta-casein, while A2 milk contains only the A2 beta-casein protein. This difference, caused by a genetic mutation, affects how the milk is digested.

No. A2 milk contains the same amount of lactose (milk sugar) as regular milk. If your digestive problems are due to a diagnosed lactose intolerance, A2 milk will not provide relief. You should consider lactose-free products instead.

When the A1 beta-casein protein is digested, it releases a peptide called beta-casomorphin-7 (BCM-7). This peptide has been linked to digestive discomfort, inflammation, and other symptoms in sensitive individuals.

The best method is a dietary elimination trial. Remove all dairy for a period (e.g., two weeks), then introduce A2 milk only. Monitor your symptoms. If you feel better, reintroduce conventional milk to see if symptoms return. The change in symptoms will help you determine if A1 protein is the issue.

Cows from ancient and certain indigenous breeds, such as Guernsey, Jersey, and some Zebu cattle, naturally produce milk with predominantly or exclusively A2 beta-casein. Conventional dairy is often a mix from breeds like Holstein.

While A2 milk may offer digestive benefits for those sensitive to the A1 protein, there is still debate and ongoing research regarding other broader health claims. Both milks offer similar nutritional content, but the potential effects of BCM-7 from A1 protein on some body systems are still being studied.

No, they are different conditions. A cow's milk protein allergy is a serious immune system response and requires complete avoidance of all milk products. A1 protein sensitivity is a digestive issue, not an allergy, and may be manageable by switching to A2 milk.