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Food Focus November 2007

The great milk debate

NZFSA, along with the rest of the world’s food safety agencies and the World Health Organization, believes milk is a safe and nutritious product. But milk seems to court controversy – the latest being the one about A1 and A2

Milk from cows, and any other milk-producing animal, can vary quite a lot in the type and amount of protein it contains. A1 milk is the most common variety in most developed nations of the world (named for the type of protein it contains), and has been the most common for thousands of years.

Cow’s milk contains six major proteins: four are casein proteins, the other two are whey proteins. Casein proteins make up about 80% of the protein in cow’s milk. Beta-casein is one of the major ones, itself made up of different kinds, depending on the genetic make-up of the cow. Milk high in beta-casein A1 is referred to as ‘A1 milk’, while milk high in beta-casein A2 is called ‘A2 milk’.

Milk produced in New Zealand, as in many other countries, normally contains a mixture of A1 and A2 beta-caseins. Different breeds can produce different milk, for example Friesian cows produce mostly A1 milk, while Guernsey cows, sheep and goats produce mostly A2 milk.

NZFSA is concerned that statements about the safety of milk will create unnecessary fears, particularly for the parents of young children, and could lead some people to avoid a food that has substantial nutritional benefits.

What is the issue?

Some research has suggested a possible link between milk protein consumption and heart disease and insulin-dependent diabetes. Researchers Dr Murray Laugeson and Professor Emeritus Bob Elliott collected data from 21 wealthy countries and reported in 2003 a significant correlation between the amount of A1 beta-casein consumed in a country and the national rate of coronary heart disease. They also found a similar correlation (from data from 19 wealthy countries) between A1 betacasein consumption and the rate of childhood type-1 diabetes.

Following this in 2004, NZFSA commissioned an independent expert, Professor Boyd Swinburn, to analyse available published literature on the A1/A2 issue.

What are the health risks?

The 2004 review commented that the correlations between A1 milk and diabetes in one study were extremely high, but it also stated that such correlations cannot establish cause and effect, that clinical studies in this area are not very helpful and the results from animal studies are mixed. It then stated that this is an area where further research is needed and could be very worthwhile.

More recently, two University of Otago professors pointed out that type-1 diabetes rates in New Zealand have escalated while milk consumption has declined. On the other hand, deaths from heart disease have dropped by 50% over the past 30 years, and most of the decline can be explained by factors unrelated to A1/A2 milk.

Cardiovascular disease is a multi-factorial disease, which means there are many risk factors. Major risk factors include smoking and high saturated fat intake; major risk mitigating factors include omega-3 fatty acid, and fruit and vegetable consumption. NZFSA believes the studies available do not provide sufficient evidence to support changing advice on the consumption of milk.

NZFSA reviews now underway

Overall, NZFSA’s position then, as now, has not changed – milk is important in our diet.

However, in light of continuing concerns regarding the food safety implications of A1/A2 milk, NZFSA has commissioned two independent reviews: firstly of the science related to A1/A2 milk; and secondly, how NZFSA came to its conclusion that there was insufficient evidence for NZFSA to change its position milk.

Dr Andrew McKenzie, Acting Chief Executive of NZFSA says: “We’ve made the decision to commission these new reviews as a result of continuing controversy in the media about consumption of New Zealand’s conventional milk supplies and about our decision-making process and exercise of our food safety mandate. We hope they will answer the concerns about the safety of milk and show that NZFSA’s science-based decision-making processes remain credible, reliable and trustworthy.”