A1 and A2 are names used to identify different proteins found in milk. the idea that A1 milk may be detrimental to health has been around for a while. Some suggest that there is a link between A1 milk consumption and Type 1 diabetes and some other illnesses. Professor Boyd Swinburn from the School of Health Sciences at Deakin University in Melbourne discusses his review into A1/A2 milk claims for the New Zealand Food Safety Authority.
Norman Swan: This morning on the Health Report – two controversies. One is the use of an antibiotic in the treatment of arthritis.
Peter Wall: They all think I’m basically lucky, I said to my wife I’m going to talk to Norman Swan about this thing, you know a lot of people don’t believe in this. And she said well I’ve seen how bad you were and I’ve seen how you are now, you should go and tell people.
Norman Swan: And the other is a row in New Zealand over milk with relevance for us here in Australia. It’s been going on for years but has blown up again in the last few weeks. The focus this time is a report critical of the New Zealand Food Safety Authority about how it handled a review into the safety of milk. The original review was conducted by a highly respected endocrinologist and former medical director of the Heart Foundation in New Zealand, Boyd Swinburn. Boyd is now Professor of Population Health at Deakin University in Melbourne.
Boyd Swinburn: Thousands of years ago there was a single genetic mutation in one of the European cows in one of the proteins that constitute milk and one of the casein molecules. That single genetic mutation alters one of the building blocks of the protein which doesn’t change a lot about the functionality of milk but it does mean that casein molecule is more susceptible to being broken at that particular place by the enzymes releasing a component which has sort of morphine like actions. And this is thought to be what might be triggering a number of diseases but this single mutation is only in some cows and this is in what’s called A1 cows, so cows will have two copies of this particular gene and the cows will either be A1/A1 so both of the genes will translate for the A1 casein molecule.
Norman Swan: The one that breaks easily?
Boyd Swinburn: The one that breaks easily or they could be A2/A2 which is the original casein molecule or it could be one copy of A1 and one copy of A2.
Norman Swan: Now it can’t be that bad for cows since there are lots of herds in the world which are A1.
Boyd Swinburn: Absolutely and that’s what cow’s milk is for, it’s for cows.
Norman Swan: So where did the idea come from that A1 might not be that brilliant for human health, apart from this theoretical thing that the molecule’s a bit more fragile and can have hormonal like effects on the body?
Boyd Swinburn: The original observation was from Professor Bob Elliott from New Zealand who is a paediatrician and noted that in Samoa there were no cases of type 1 diabetes, that’s the type of diabetes that occurs in children and requires insulin but when he was acting as a paediatrician in Auckland there were a reasonable number of cases of Samoan children with type 1 diabetes. So he started looking into the background and into the diet of both those populations and asked himself what might be the trigger and one of the big differences in their diet when they lived in New Zealand they had quite a higher milk consumption. Now there are quite a few populations around the world that have very high milk consumptions and one population in particular the Masai in Africa virtually live off milk because they are cow herders and the Masai don’t get type 1 diabetes. So he asked them is there any difference in the milk that the Masai drink compared to what’s available in New Zealand. And the scientists said yep, the original African cattle are all A2/A2 cattle and they don’t have this A1 gene which is more in the black and white, the Fresian type herds that are more common in European countries and in New Zealand and Australia. So that led him down a path looking at this as a potential trigger.
Norman Swan: Before you go on though if you look around the world with type 1 diabetes, for example if you take New Zealand there’s going to be more type 1 diabetes in Invercargal compared to Auckland and in Australia there’s more type 1 diabetes in Hobart compared to say Cairns because around the world the further away you get from the Equator the more type 1 diabetes you get and it’s thought to be due to infections in more temperate climates and that sort of thing. Isn’t that the explanation rather than the milk?
Boyd Swinburn: Well there is a gradient of latitude and people have talked about what might be the mechanism for that, some people are looking at vitamin D as a potential component in the pathway. There is a latitude effect but when Professor Elliott and some other researchers got estimates of type 1 diabetes incidence rates at a whole of country level and compared it with whatever known factors there were, including latitude, but also including this mixture of A1/A2 milk consumption, latitude did have an effect but it wasn’t nearly as strong a correlation as the consumption of A1 milk.
Norman Swan: Now this became a cause célèbre in New Zealand and an agricultural scientist called Keith Woodford who has written books on it and you were asked to do a review.
Boyd Swinburn: That’s right it did take off in New Zealand primarily because of the work of Bob Elliott and another person Corey McLaughlin who picked this up and also noted the relationship with heart disease and they were trying to develop this up as a business at the same time as trying to find some evidence to back it up. I was asked in 2004 by the New Zealand Food Safety Authority to review the evidence on A1/A2 milk consumption and human health and at that stage there were these correlational studies across countries which were very strong I have to say, we don’t usually see such strong correlations in these cross country studies as we found with A1 milk. It was backed up to some degree by some human studies and some animal studies but really not firm enough evidence to warrant major changes in the way the governments communicated messages to the public about milk or strong enough to warrant health warnings or anything like that on milk. But nevertheless these findings were still extremely interesting and intriguing and potentially very important at a public health level.
Norman Swan: And that’s what you concluded in your study?
Boyd Swinburn: That’s right and we obviously were very keen to see more research in this area and I have to say it’s been relatively disappointing how little this has been taken up in research, I think scientists have been a little bit frightened off.
Norman Swan: Did you think it was a little bit nutty before you came in to it?
Boyd Swinburn: Well I didn’t know very much about it at all I have to say.
Norman Swan: And when you looked at the evidence was it strong for heart disease, as strong as for type 1 diabetes?
Boyd Swinburn: No not as strong for heart disease as it was for type 1 diabetes and there have been other suggested associations again with schizophrenia and autism and of course once you start getting a long list of these very different diseases or health problems supposedly caused by a single triggering agent it makes one a little bit suspicious about that. So I think we have to be very cautious about what the evidence shows.
Norman Swan: And the other thing that makes us suspicious is that they tried to bury your report.
Boyd Swinburn: Well the New Zealand Food Safety Authority asked me to do it, there was quite a long lead time, they sent it out for peer review, there’s quite a lead time before it was made public. I was asked to include in it a lay summary – now this turned out to be a major point of contention and New Zealand Food Safety Authority didn’t publish my lay summary.
Norman Swan: Basically this was a summary that anybody without scientific education could read and understand?
Boyd Swinburn: That’s right but also it was also a little bit interpretative as to what this might mean for the public whereas the body of my report stuck fairly close to the evidence and the conclusions but of course but what people wanted to know is well what does this mean for me. And that’s actually a very difficult message to communicate because what you’re communicating is potential risks for some people but also at the same time a lot of uncertainty around the evidence. So this is not an easy task to do but I sort of put myself in this position so I thought well, here am I, I’m a middle age male, I don’t have heart disease or diabetes, do I go and look for A2 milk? Well actually, no I don’t. What about if I were, to put myself in an extreme case, what say I was about to have a child and there was a lot of type 1 diabetes in the family, would I keep my new child free from cow’s milk exposure for the first few years? And I think I probably would because I’d be taking a precautionary approach, I’m not certain about the evidence but it would seem a worthwhile step to take.
The implications are different for different populations and that’s not an easy thing to communicate and I think it was one of the things the NZFSA were not that happy to communicate.
Norman Swan: And they released it on a weekend when you were not around?
Boyd Swinburn: They released it at a time when I wasn’t and I specifically told them that I wasn’t going to be available which annoyed me a lot and all of these things got Keith Woodford interested in why was NZSFA potentially doing this and communicating it in this way and saying that milk was perfectly safe when I never said that in my report. So he became quite intrigued by the whole thing and wrote a book about it called The Devil in the Milk.
Norman Swan: And the allegation is that the New Zealand dairy industry has heavily lobbied here?
Boyd Swinburn: Well the New Zealand dairy business Fonterra in particular is far and away New Zealand’s biggest company and milk is a huge export for New Zealand. So obviously there are huge interests in this and it’s this mixture of major commercial interest coupled with potential population health that is really quite a volatile mix and he explored whether indeed companies had been giving undue influence on the communications coming out of NZFSA.
Norman Swan: And a report a couple of weeks ago criticised the New Zealand Food Safety Authority for the way they handled this.
Boyd Swinburn: Yes and indeed and following the publication of Keith Woodford’s book that caused quite a storm in New Zealand, they did get this independent reviewer and he did criticise how they had handled my report and how they’d communicated this to the public. I think that the public warrant being given a full explanation along with the uncertainties that all that implies. So it’s not an easy thing to do but I think it’s something we have to do.
Norman Swan: What’s the Australian herd?
Boyd Swinburn: The Australian herd I believe is similar to the New Zealand herd – the New Zealand herd is around about 50% to 60% A2 at the moment and there’s a gradual shift I understand towards A2 because in the past cows had been genetically selected for being large cows and being able to produce high volumes of milk. Now cows are selected much more for their efficiency and feed conversion and in the protein production of their milk and so A2 cows apparently are slightly better at that so just for other reasons there is a bit of a drift towards selection of A2. So slowly the herd is changing in NZ and that may well be the case in Australia but when we think through what can be the potential actions that could be taken indeed it’s really the dairy farmers that have the choice and can take the action. Over a period of say 8 to 10 years, if all dairy farmers selected A2 semen from A2 bulls for their breeding program then within that period of time the whole herd actually in the country could be changed over to A2 cows.
Norman Swan: And nothing would be lost.
Boyd Swinburn: Nothing would be lost, there’s no cost to that, certainly in New Zealand there’s no cost I’m not sure about Australia but there’s no cost to it, all the bulls are typed anyway and there’s no potential detrimental effect. So I have been rethinking my position on this and particularly in relation to what the communication should be to dairy farmers.
Norman Swan: And just recently you’ve written about it, at least to New Zealand dairy farmers, saying really they should just convert to becoming an A2 herd.
Boyd Swinburn: That’s right and at a recent international diabetes meeting in Wellington where this issue was on the agenda and we discussed it amongst people who had been involved it became clear to me that the dairy farmers are the change agents, for them the communication I think is quite simple that there’s no cost and no detriment so they should change. But nobody was really communicating that to them, certainly the government wasn’t and it’s probably not appropriate I don’t think for the government to make that communication to dairy farmers and of course for the dairy industry and in New Zealand Fonterra in particular to make that communication to dairy farmers of course itself is a bit fraught. It’s a difficult communication on the one hand to say to dairy farmers you should be switching to A2 herds and on the other hand saying to the New Zealand public continuing to drink A1A2 mixed milk is perfectly fine. So that’s a difficult communication for a company like Fonterra.
Norman Swan: If you wanted to buy A2 milk in Australia how would you know how to get it?
Boyd Swinburn: A2 milk is available in shops, it’s quite a lot more expensive than regular milk and it’s not available everywhere but those people who search it out can find it.
Norman Swan: Does processing milk to produce these new low fat products change the casein or does the A2 sort of perpetuate through whatever milk you drink?
Boyd Swinburn: I’m not a protein chemist so I’m not sure how much it is affected by the processing. What does seem to be apparent is that the processing that occurs in the production of cheese does seem to somehow kind of negate this effect certainly from the evidence internationally when you take cheese out of the equation, out of the relationship, the relationship becomes much stronger. So it seems to be that A1 cheese doesn’t necessarily convey this apparent risk. So there may well be quite a lot of nuances within the processing that haven’t been fully explored yet.
Norman Swan: Boyd Swinburn is Professor of Population Health at Deakin University in Melbourne. The book he mentioned is by Keith Woodford and it’s called Devil in the Milk and it’s published by Craig Potton.
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