🥛 A2 milk

A2 milk is cow’s milk in which β-casein is present only as the A2 variant. Cows have two main variants of this protein, A1 and A2; they differ by a single amino acid at position 67 (proline in A2, histidine in A1). Digesting A1 β-casein releases the peptide beta-casomorphin-7 (BCM-7), while A2, according to available data, releases much less of it.

The A1 variant is thought to have arisen several thousand years ago in European cattle and spread through breeding, whereas the milk of many Asian and African breeds, as well as goat, sheep and buffalo milk and human milk, contains A2-type β-casein. Cows with the A2/A2 genotype are identified by a genetic test; commercial A2 milk appeared in New Zealand in the early 2000s.

A2 milk or regular milk? The only difference is the type of β-casein: regular cow's milk is a mix of A1 and A2, A2 milk contains only A2. Digesting A1 releases the peptide BCM-7, A2 much less. Fat, lactose and calcium stay the same, so A2 milk is not a lactose-free milk and cannot replace one. Goat, sheep and buffalo milk and human milk also carry A2-type β-casein, and the evidence for benefits of A2 milk over regular milk is still limited.

On a carton, “A2” names the type of β-casein; it does not mean lactose-free, organic or a particular breed. Look for wording such as “A2 milk” or “contains only A2 β-casein” next to the usual terms: whole, semi-skimmed, pasteurised or UHT. If sold near you, it sits in the milk section of supermarkets or health food shops. Always read the label for lactose, because an A2 pack has as much as regular milk.

Scientific evidence on the benefits of A2 milk is limited. In 2009 the European Food Safety Authority (EFSA) concluded that a cause-and-effect relationship between BCM-7 and non-communicable diseases had not been established. Research reviews note that A2 milk may cause less digestive discomfort in some people, but the evidence base is small. A2 milk contains the same amount of lactose as regular milk.