A2 Milk by Donagh Berry

Introduction

Approximately 25-30% of cow’s milk is beta-casein (ß-casein). There are several types of ß-casein, the most common of which are A1 and A2 – other types include A3, B, C, D, E, F, G, H1, H2, and I. It is thought that the A2 variant was the original variant with the A1 mutation originating approximately 5,000 to 10,000 years ago. A2 milk currently commands twice the price of regular milk in the southern hemisphere, and this milk type is now migrating onto European and US supermarket shelves. The question remains, is A2 milk the next trend in dairy? This was the question posed at the recent VistaMilk A2-milk Masterclass held in Teagasc Moorepark for Vistamilk members.

A1 milk and human health – ß-casomorphin (BCM-7)

There is a hypothesis that consumption of the A1 ß-casein has unfavourable health implications, most notably increasing the incidence of Type-I diabetes, ischaemic heart disease (the major cardiovascular disease) and as well as intensifying the symptoms of some neurological conditions such as autism, schizophrenia, post-partum depression, and sudden infant death syndrome.

Digestion of A1 ß-casein in the human small intestine releases a bioactive seven-amino-acid peptide, ß-casomorphin (BCM-7) which is known to have opioid properties. The hypothesis of the impact of BCM-7 on human health is that BCM7 enters circulation in susceptible people and suppresses immune surveillance or response to antigenic agents as well as possibly crossing the blood:brain barrier and influencing neurological function. Any effect of BCM-7 on human health is thought to only exist is individuals suffering from “leaky gut” which includes infants as well as possibly people on antibiotics; coeliacs are also thought to be potentially at risk.

The scientific evidence to support most of these hypothesise is, however, at best, weak. As was demonstrated in the European Food Safety Report (2009), a causal relationship could not be established between the consumption of the BCM-7 and the incidence of the various pathologies. On top of this Dr Ian Givens at the recent VistaMilk A2 Milk Masterclass in Moorepark presented results from published studies using animal models to examine the impact of A2 or A1 milk on a variety of pathologies such as diabetes, cardiovascular diseases and Neurological disorders. For each of these pathologies, no difference between A1 and A2 milk was observed, or the trends were far from conclusive; evidence that A1 beta-Casein is related to schizophrenia is very scant.

A2 milk and the cow

The difference between whether a cow produces A1 and A2-type milk is simply one DNA variant within the whole three billion pieces of DNA. The variant is called a SNP (pronounced “snip”) and we know where that DNA variant is. All animals genotyped in Ireland have information on whether or not their animals carry that DNA variant. The DNA variant is directly inherited from the parents and is also directly transmitted to the offspring. There are three possible genotypes of cows for the A2-type milk. The frequency of variants in Irish cows is in the Table below. A1A1 cows are those that have two copies of the A1 variant and they produce only A1-type milk. A2A2 cows are cows that have two copies of the A2 variant and only produce A2-type milk. A1A2 cows produce a mixture of A1 and A2 milk.