How Do I Tell If My Milk Is A1 or A2?

October 29, 2025 •

4 min read

Most dairy milk sold today contains a mix of A1 and A2 beta-casein proteins, a legacy of a genetic mutation that occurred in European dairy herds thousands of years ago. This guide explains how do I tell if my milk is A1 or A2, detailing the key differences and the reliable methods for verification, as you cannot tell by taste or appearance alone.

Quick Summary

The difference between A1 and A2 milk lies in a single amino acid within the beta-casein protein, but this can affect how it's digested. Without taste or visual cues, the only definitive way to know if milk is A1, A2, or a mixture is through genetic testing of the cow or laboratory analysis of the milk itself. Some individuals report less digestive discomfort with A2 milk, which may be linked to the absence of the peptide BCM-7 produced during A1 protein digestion.

Key Points

No at-home test exists: It is impossible to tell if milk is A1 or A2 by taste, smell, or appearance alone, as the difference is at the molecular protein level.
Difference is a single amino acid: The distinction comes from one amino acid at position 67 of the beta-casein protein, which affects how it is digested.
A1 releases BCM-7: When digested, A1 beta-casein can release a peptide called BCM-7, which is linked to digestive discomfort in sensitive individuals.
A2 is considered gentler: A2 milk does not release significant amounts of BCM-7, and many people report easier digestion with it compared to regular milk.
Check the label for certification: The only reliable way to know your milk's type is to buy products specifically labeled as 100% A2, which means the cows and milk have been genetically tested.
Consider cow breed: Milk from certain breeds like Jersey, Guernsey, and native Indian cows is more likely to be A2, while milk from Holsteins and Friesians is typically A1 or mixed.
Distinguish from lactose intolerance: Symptoms of A1 protein sensitivity can mimic lactose intolerance, so it's important to consider which protein, not just the sugar, may be causing your discomfort.

The Core Difference: A Single Amino Acid

The fundamental distinction between A1 and A2 milk is a minute genetic difference in the beta-casein protein. Beta-casein is one of the two main protein types in cow's milk. The A2 variant is the original form of this protein, found in older cow breeds and most non-bovine dairy, such as goat and human milk. The A1 variant emerged later through a natural genetic mutation in some European cow breeds.

This difference comes down to a single amino acid at position 67 of the beta-casein protein chain. In A1 beta-casein, this position is occupied by histidine, while in A2 beta-casein, it is proline. This seemingly small change has a significant downstream effect on how the protein is digested. During digestion, the histidine in the A1 protein allows for the release of a bioactive peptide called beta-casomorphin-7 (BCM-7). In A2 milk, the presence of proline creates a stronger protein structure that prevents BCM-7 from being released.

Why You Can't Tell A1 or A2 Milk Apart at Home

Trying to identify milk type by flavor, smell, or consistency is a futile exercise. A1 and A2 milk taste identical and have the same nutritional profile in terms of fat, sugar (lactose), and minerals. The differentiating factor is only visible at a molecular level, requiring specialized testing equipment.

The limitations of at-home assessment:

Taste and texture are identical: There is no distinguishable difference in flavor, color, or creaminess between A1 and A2 milk.
Digestive symptoms are not diagnostic: While some people report improved digestion with A2 milk, symptoms like bloating and gas are common to many milk intolerances, including lactose intolerance and allergies. Relying on symptoms alone can be misleading.
Cross-contamination is likely: The vast majority of commercially available milk is a pooled mix from large dairy herds, which typically include both A1/A1, A1/A2, and A2/A2 cows. Unless explicitly labeled as A2, you can assume your milk is a blend.

How Dairy Companies Ensure A2 Status

To confidently market milk as A2, companies follow a stringent process that involves genetic testing and supply chain segregation. This is the only way to be certain of the milk's protein composition.

The A2 testing process:

Genetic testing of herds: Farms that produce A2 milk genetically test each cow in their herd, often using a hair or tissue sample. A cow with an A2/A2 genotype produces only A2 beta-casein, while an A1/A1 cow produces only A1. An A1/A2 cow produces a mixture. Only milk from A2/A2 cows is used for pure A2 products.
Segregated farming: A2/A2 cows are kept in separate herds and milked with dedicated equipment to prevent cross-contamination from A1-producing cows.
Milk testing: After collection, the milk is tested again using advanced laboratory methods to verify its purity.

Scientific Methods for A1/A2 Testing

For precise analysis, scientists and dairy manufacturers rely on advanced laboratory techniques that can detect the specific amino acid variants. These methods are not available for consumer use but are crucial for ensuring the integrity of A2-labeled products.

Laboratory testing methods include:

Mass Spectrometry (MS): Advanced techniques like High-Performance Liquid Chromatography-Mass Spectrometry (HPLC-MS/MS) can analyze the protein fragments after digestion to determine the exact proportion of A1 and A2 beta-casein present in a sample.
Infrared Spectroscopy (FTIR): Fourier-transform infrared (FTIR) spectroscopy, combined with chemometric analysis, can also be used to classify milk samples as A1 or A2 based on their spectral data.

Comparison Table: A1 vs. A2 Milk


Feature	A1 Milk	A2 Milk
Protein Variant	Primarily contains A1 beta-casein, often mixed with A2.	Contains only A2 beta-casein protein.
Key Amino Acid	Histidine at position 67 of the protein chain.	Proline at position 67 of the protein chain.
Digestion Byproduct	Releases beta-casomorphin-7 (BCM-7) during digestion.	Releases little to no BCM-7 during digestion.
Associated Digestion	Linked to digestive discomfort, bloating, and gas in some individuals due to BCM-7.	Associated with easier digestion and less discomfort for some sensitive individuals.
Cow Breeds	Found in most modern Western breeds, such as Holstein and Friesian.	Found in older native breeds, like Jersey, Guernsey, Gir, and some Zebu cattle.
Appearance & Taste	Identical to A2 milk in appearance, taste, and texture.	Identical to A1 milk in appearance, taste, and texture.
Testing Method	Can only be identified through genetic or laboratory protein analysis.	Requires genetic testing of cows and subsequent milk analysis for certification.

What to Look for on the Label

Given that at-home testing is not possible, your best bet is to rely on product labeling. Brands selling pure A2 milk will proudly advertise this fact on their packaging. Look for clear statements like "100% A2 Protein," "A2/A2 Verified," or similar language.

Common A2 milk products include:

a2 Milk® (The a2 Milk Company)
Alexandre Family Farm Organic A2/A2 milk
Specific branded products from companies that test their herds and keep them segregated.

If a product simply says "milk" and is from a conventional source, it most likely contains a mixture of A1 and A2 proteins. Be mindful that even some organic milk can be A1 milk.

Conclusion: The Definitive Method for Identification

Determining whether your milk is A1 or A2 is impossible with the naked eye or sense of taste. The difference is a genetic one, impacting how a specific beta-casein protein is digested, and potentially causing discomfort for some people. The only definitive way to know the protein makeup of your milk is to purchase products explicitly labeled as A2, which guarantees the dairy herd and final product have been genetically verified and tested through strict laboratory methods. If you experience digestive issues with regular milk, trying a certified A2 brand is a reliable way to test if the protein type makes a difference for you, as the symptoms are often confused with lactose intolerance. For more information on the science behind dairy proteins, the National Institutes of Health (NIH) is a good resource to start your research from.

Frequently Asked Questions

No, you cannot taste any difference between A1 and A2 milk. The change is in a single amino acid within the protein structure, and it does not affect the flavor, color, or texture of the milk.

No, A2 milk has the same amount of lactose (milk sugar) as regular cow's milk. It is not a lactose-free product and is not suitable for individuals with a confirmed lactose intolerance unless it is also specifically processed to be lactose-free.

Milk companies ensure their product is A2 by genetically testing each cow in their herd. Cows confirmed to have the A2/A2 genotype are separated, and their milk is collected and processed in isolation to prevent any cross-contamination from A1 milk.

Most indigenous Indian cow breeds, such as Gir and Sahiwal, are predominantly A2. However, due to cross-breeding, there is a possibility that some indigenous cows could produce milk with A1 protein. It is always safest to rely on a brand that tests and certifies its product as 100% A2.

No, there is no simple or reliable test for consumers to perform at home to determine if milk is A1 or A2. The differentiation requires specialized, expensive laboratory analysis of the proteins, such as mass spectrometry.

Lactose intolerance is the inability to digest milk sugar (lactose), while A1 protein sensitivity is a reaction to the beta-casomorphin-7 (BCM-7) peptide released from A1 protein. Both can cause similar digestive symptoms like bloating, gas, and cramps, but they are different conditions.

No, being organic does not guarantee that milk is A2. The organic certification pertains to farming practices, not the genetic makeup of the cow's milk protein. You must specifically look for an A2 label.