A2 vs A1 milk: what actually differs, and what is not proven
A1 and A2 are two forms of beta-casein, a protein that makes up about a third of the casein in cow's milk. They differ by one amino acid at position 67 of the chain: proline in A2, histidine in A1. That single substitution is the whole chemical difference. Whether it matters to human health has not been established.
What beta-casein is
About four-fifths of the protein in cow's milk is casein, and beta-casein is roughly a third of that. It occurs in several genetic variants; A1 and A2 are by far the most common. The variants are inherited: each cow carries two copies of the gene and may be A2A2, A1A2 or A1A1. A2A2 cows give milk containing only A2 beta-casein; the other two give milk with both.
Which cows carry which
A2 is the original form. The A1 variant arose as a mutation in European cattle (Bos taurus) several thousand years ago and spread with the breeds that were later selected for high milk yield. The pattern today, by breed, is broadly this:
| Cattle | Typical beta-casein |
|---|---|
| Indigenous Indian breeds (Bos indicus): Gir, Sahiwal, Red Sindhi, Tharparkar, Kankrej, Rathi | Almost entirely A2 |
| Guernsey | Predominantly A2 |
| Jersey, Brown Swiss | Mixed, often leaning A2 |
| Holstein-Friesian and most high-yield European dairy cattle | Mixed, with A1 common |
| Indian crossbreds (indigenous x Holstein or Jersey) | Mixed; depends on the individual animal |
Breed is a strong indicator but not a guarantee. The only way to be sure of a particular cow is a genetic test. Which Indian cow breeds give A2 milk and What makes Gir cows different from crossbred cattle cover the breeds in more detail.
Why anyone thinks the difference matters
When A1 beta-casein is digested, the histidine at position 67 makes the chain easier for digestive enzymes to cut at that point, releasing a seven-amino-acid fragment called beta-casomorphin-7 (BCM-7). The proline in A2 resists that cut, so A2 milk releases far less BCM-7. This part is well demonstrated in the laboratory. BCM-7 is an opioid-like peptide, and the hypothesis, first raised in the 1990s, is that it has effects on the body. That is where the established facts end and the claims begin.
What is claimed, and what the evidence shows
A1 beta-casein and BCM-7 have been proposed as contributing factors in type 1 diabetes, heart disease, autism and digestive discomfort. The evidence for each is as follows.
- Chronic disease. The European Food Safety Authority (EFSA) reviewed the published evidence in 2009 and concluded that a cause-and-effect relationship between dietary BCM-7 and any non-communicable disease could not be established. That review remains the most thorough independent assessment. Early studies linking A1 milk to diabetes and heart disease were population correlations, which cannot show cause.
- Digestion. Several small human trials since 2014 have reported less bloating and discomfort, and some changes in inflammatory markers, when people who say milk upsets them drank A2-only milk rather than ordinary milk. The trials are small and a number were funded by a company that sells A2 milk. Independent reviewers describe this evidence as promising but limited, and not as proof.
- Autism and other conditions. No controlled evidence supports a link.
In India, the regulator's position is procedural rather than scientific. In August 2024 the Food Safety and Standards Authority of India (FSSAI) issued an advisory telling sellers to remove A1 and A2 claims from products, on the ground that its regulations do not define them. It withdrew the advisory five days later for further consultation. As of this writing the terms remain undefined in Indian food standards: a seller may print A2, and nobody checks it.
The honest summary: the chemistry is real, the digestion hypothesis is plausible and under study, and no health benefit of A2 over A1 milk has been established.
What this means for ghee
Ghee is almost entirely fat. When butter is clarified, the water boils off and the milk solids, which carry the protein, are browned and strained out. Whatever beta-casein the milk contained is removed with them; only traces can remain. So A2 ghee is a statement about the milk the ghee was made from and the breed of cow that gave it, not a claim that the ghee contains a different protein. Any difference between A1 and A2 milk, if one is ever established, would apply to milk far more than to ghee. What is actually in ghee and Is all ghee lactose free? set out what survives the process.
Why Organic Farmz uses Gir milk anyway
Organic Farmz makes its ghee from the milk of Gir cows, an indigenous breed whose milk is A2, and says so on the jar because it is true and because buyers ask. The reasons for keeping Gir cows are the breed itself (an Indian cattle breed suited to the climate), the taste and colour of ghee made from its milk, and the traditional preference for desi cow ghee. Organic Farmz does not claim that its A2 ghee treats, prevents or improves any medical condition. The ghee is made by the bilona method in Delhi, after each order, and is sold by the litre: Rs 1,400 a litre for 1 to 2 litres, Rs 1,300 a litre for 3 to 4 litres and Rs 1,200 a litre for 5 litres or more. Why A2 ghee costs more explains the price, and this earlier article covers the same ground from the kitchen side.
Sources
- European Food Safety Authority, Review of the potential health impact of beta-casomorphins and related peptides, EFSA Scientific Report (2009) 231, 1-107.
- Food Safety and Standards Authority of India, advisory on A1/A2 claims dated 21 August 2024, and withdrawal notice dated 26 August 2024.
- Brooke-Taylor S. et al., "Systematic review of the gastrointestinal effects of A1 compared with A2 beta-casein", Advances in Nutrition 8(5), 2017.
Questions people ask
What is the actual difference between A1 and A2 milk?
One amino acid. Beta-casein is a chain of 209 amino acids; in the A2 form position 67 is proline, in the A1 form it is histidine. Everything else about the two milks, including fat, lactose, calcium and total protein, is the same for cows of the same breed and diet.
Which cows give A2 milk?
Indigenous Indian cattle (Bos indicus) such as Gir, Sahiwal, Red Sindhi, Tharparkar and Kankrej produce almost entirely A2 milk, as do some European breeds such as Guernsey. Holstein-Friesian cows commonly carry A1. Crossbred herds give mixed milk. Breed is a strong indicator, but only a genetic test of the individual cow is a guarantee.
Is A2 milk proven to be healthier than A1 milk?
No. The European Food Safety Authority reviewed the evidence in 2009 and concluded that a cause-and-effect relationship between A1 beta-casein (or the peptide BCM-7 it releases) and any disease could not be established. Later small trials report less digestive discomfort with A2-only milk in some people, but reviewers describe that evidence as limited.
Does A2 milk have less lactose?
No. A1 and A2 describe a protein, not the sugar. A2 milk contains the same lactose as any other cow milk and is not suitable for someone with lactose intolerance on that basis.
Is A2 ghee different from ordinary ghee?
Only in the milk it came from. Ghee is almost pure fat; the protein, including beta-casein, is removed with the milk solids during clarifying. A2 ghee therefore tells you the breed of cow, not that the ghee contains a different protein.
Does FSSAI recognise A1 and A2 milk?
Not in its standards. In August 2024 FSSAI issued an advisory asking sellers to remove A1 and A2 claims from labels because its regulations do not define them, then withdrew the advisory five days later for further consultation. The terms remain undefined in Indian food standards; the claim is permitted but not regulated.
Why does Organic Farmz call its ghee A2?
Because it is made only from the milk of Gir cows, an indigenous breed whose milk carries the A2 beta-casein. The label describes the source milk. Organic Farmz does not claim that A2 ghee treats, prevents or improves any health condition.
Can you test whether milk is A2?
Yes. A laboratory can genotype the cow from a hair or blood sample for the beta-casein gene, or analyse the milk protein directly. There is no reliable home test.