What does A2/A2 mean in milk?

A2/A2 milk comes from cows whose beta-casein is homozygous A2, meaning the cow only produces the A2 protein variant and not the A1 variant. A1 beta-casein produces a peptide called BCM-7 during digestion that some people associate with digestive discomfort.

Is A2/A2 milk easier to digest?

Yes. People who cannot tolerate regular cow milk routinely tolerate A2/A2 without symptoms. Clinical studies (Jianqin 2016, Sheng 2019) confirmed that A1 milk causes digestive symptoms that A2/A2 milk does not. The difference is the BCM-7 peptide, which only A1 milk produces during digestion.

Which breeds are A2/A2?

Jersey and Guernsey cows have high A2 frequency (60 to 90% A2/A2). Brown Swiss is moderate to high. Holstein is split, with selective breeding increasing the A2/A2 fraction. Goat and sheep milk do not contain A1 beta-casein at all.

Can I get raw A2/A2 milk?

Yes, where state law allows raw milk sales. Use the farm-to-door directory and apply both the Raw milk and A2/A2 dairy filters.

A2/A2 dairy: what it is, how to find it, and is it actually different

The actual genetic difference

Cow milk contains beta-casein, one of the major milk proteins. Beta-casein has two common genetic variants: A1 and A2. The two differ by a single amino acid (proline at position 67 in A2, histidine in A1). When A1 is digested, the body cleaves off a 7-amino-acid peptide called BCM-7 (beta-casomorphin-7). A2 does not produce BCM-7.

BCM-7 has opioid-like activity, slows gut transit, and drives inflammation. The strongest clinical studies (Jianqin et al. 2016, Sheng et al. 2019) found that A1 milk caused measurable digestive symptoms that A2/A2 milk did not. People who cannot tolerate regular cow milk routinely tolerate A2/A2 just fine.

What A2/A2 means in practice

A2/A2 designates a cow whose beta-casein is homozygous A2 (both copies are A2). Such cows produce milk with no detectable A1 beta-casein and therefore no BCM-7 in the milk. A2/A1 heterozygous cows produce a mix.

Which breeds tend to be A2/A2

Jersey: high A2 frequency, often 60% to 80% of a herd is A2/A2.
Guernsey: very high A2 frequency, often 90%+ A2/A2.
Brown Swiss: moderate to high A2 frequency.
Holstein: split, around 30% to 40% A2/A2 in conventional herds; selective breeding raises this.
Goat and sheep milk: do not contain A1 beta-casein at all (different protein structure entirely).

A herd is A2/A2 when every cow is genetically tested and confirmed homozygous A2. This is a deliberate breeding decision; most US grocery milk is a blend.

Who feels the difference

Anyone who has had stomach trouble with regular cow milk. Anyone who tolerates goat milk but not cow milk. Anyone whose kids react to store-bought milk. A2/A2 cow milk is gentler than A1 milk in every population that has been studied. People with a true IgE-mediated milk protein allergy react to all dairy and should avoid it; everyone else is a candidate to try A2/A2.

How to find A2/A2 milk

Use the farm-to-door directory and apply the A2/A2 dairy filter. Farms that have herd-tested for A2 status and produce exclusively A2/A2 milk are tagged. You can additionally apply the Raw milk filter to find raw A2/A2 milk specifically.

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