Professor of Farm Management and Agribusiness at New Zealand’s Lincoln University, Keith Woodford, has authored the book Devil in the Milk which took a close look into the health implications associated with A1 and A2 beta-casein proteins in milk.
After reviewing evidence of more than 100 scientific papers linking beta-casein types to a range of medical conditions, including Type 1 diabetes in children, Woodford put his findings before the Western-Pacific International Diabetes Federation Congress in Wellington on 2nd April.
This served as one of the reasons why the author of the New Zealand Food Safety Authority’s first review of A1 and A2 beta caseins, Professor Boyd Swinburn, is now recommending that the NZ dairy industry should be moving to A2 milk production.
All in the genes
Cows have traits, inherited through their genes, to produce different naturally occurring forms of their major milk proteins. Beta casein, makes up to a third of the protein content of cows milk, and has an excellent nutritional balance of amino acids.
There are two main forms of beta casein protein found in the milk of dairy cows: A1 and A2 beta casein which differ from each other by one amino acid. Which beta casein genes the cow has inherited determines what form of beta casein will be produced in their milk.
Each cow carries two copies of the beta casein gene and of these, both can be for A2 beta casein, containing only the A2 form of beta casein; both can be for A1 beta casein, containing only the A1 form of beta casein; or the milk can contain equal amounts of A1 and A2 beta casein.
A simple DNA test allows easy identification of which of the beta casein forms it carries. The proportion of A1 to A2 beta casein in cows’ milk varies between breeds. Holstein cows’ milk contains on average a balance of 50% A1 beta casein and 50% A2 beta casein. Other breeds such as Jersey and Guernsey cows can have a higher proportion of A2 beta casein in their milk. This is due to more Jersey and Guernsey cows carrying the A2.
The A1 variant beta casein in cows’ milk is unique amongst all mammalian beta caseins, in having a histidine amino acid at this position. Other species milk contains beta casein that can be considered A2 like, as they have a proline amino acid at this equivalent position in their beta casein chains. Water buffalo, yak, goat as well as human breast milk all contain exclusively the A2-like form of beta casein.
The origin of cows
A2 beta casein has been recognized as the original type of beta casein protein that would have been produced by the first domesticated cows, from which the others evolved.
Research indicates that A2 may be regarded as the original or “progenitor” (direct ancestor) form of beta casein gene of the bovine animals that cattle belong to. A2 beta casein is found in all types of bovine animals (all western, African and Indian cattle including the water buffalo). A1 beta casein is found primarily in western dairy cows and is thought to have arisen by natural evolution.
A2 rich milk has been the centre of many international studies that link A2 beta casein to a reduction of health risks. The health effects of A2 beta casein are thought to be due to the bioactive peptides it releases.
According to Woodford, cows must be tested to establish whether their milk contains the A1 or A2 form of the protein; A2 cows should then segregated and their milk kept in isolation to avoid contamination with the A1 form.
“What we’ve got to do is breed the herds across to pure A2. In NZ what we’ve found is that most of our top bulls are actually purely A2 so we can get the herds across to A2 reasonably quickly.
“What we’re saying to farmers in NZ is that you can shift across to A2 without any costs because you can still get the very best bulls, so just go on and do it. But we’re not actually quite that far down the track in Australia because a lot of farmers would not be aware of that yet.
“The debate is not about whether milk is nutritious. Rather, the debate is about whether for some people there are health risks associated with one particular variant of beta-casein that is produced by some cows. I also get many emails from people who say they cannot drink ordinary milk but that they can drink A2,” said Woodford.
“If we just look at the science alone, for me personally the story is quite convincing. But in addition, when you talk to people who are intolerant to ordinary milk and have tried A2 milk, most of them are saying they can tolerate the A2 milk. They are convinced that it is a real effect and not just something that they want to feel. I think it all adds to the total picture.”
The growing interest in the potential effects of A1 and A2 beta-caseins on human health is reflected in the announcement of the European Food Safety Authority’s (EFSA) extensive review of the research and data relating to these two protein variants. The EFSA expects that the review findings will be published towards the end of the year.
All in the book
Professor Woodford’s Devil in the Milk is the first book examining the link between one of the proteins in the milk we drink to a range of serious illnesses to be published internationally. In the book Woodford examines the population studies that look at the link between the consumption of A1 milk and the incidence of heart disease and Type 1 diabetes; explains the science that underpins the A1/A2 hypothesis; and examines the research undertaken with animals and humans.
“I’m just keen to get the story out there. When I became aware of the issues and started researching them, I realised that there were some pretty powerful forces trying to stop the information. I think it’s an important story and it needs to be told.
“If people read the book and disagree, then that’s their decision because I’ve at least put the facts out there. What I find though is that 95 or even 99% of people do in fact become convinced once they read the book. Then what I’ve done is put the person in a position where they can make their own decision. And that’s really all I’m trying to do. I’m not trying to sell A2 milk and there’s nothing in it for me. I’m just telling an important story.”
Lena Zak is the editor of FOOD Magazine.