Claims of Conventional Milk Risks Unjustified

Claims of Conventional Milk Health Risks Unjustified

Tuesday 18 September 2007

Professor Keith Woodford, a professor of Agricultural Economics at Lincoln University, has claimed that appreciable health risks – including heart disease and type 1 diabetes – result from consumption of conventional milk supplies which contain a protein A1 beta-casein. We believe that such a claim is unjustified on the basis of current scientific evidence.

* Much of the "evidence" is based upon correlation studies – that is countries with high disease rates have a high consumption of milk with the A1 protein. It is universally accepted by those with expertise in population studies that such studies generate clues for further research rather than provide evidence of cause. They can sometimes generate notoriously unreliable results. In the case of the A1 disease associations, there are several inconsistencies. For example, type 1 diabetes rates have escalated in New Zealand and many other countries in recent years, whereas consumption of milk and many dairy products have declined. Heart disease death rates in New Zealand have dropped by 50 per cent in men and women over the past 30 years. Most of this decline can be explained by favourable changes in risk factors such as smoking, blood pressure, and blood cholesterol - factors, unrelated to A1/A2 milk consumption. Furthermore, we know that almost 90 per cent of the difference in heart disease death rates between countries can be explained by differences in obesity, physical activity, smoking, blood cholesterol, blood pressure, diabetes and fruit and vegetable consumption. If A1 milk causes heart disease, its effect pales in comparison with the real risk factors for heart disease.

* There have been several previous attempts to incriminate components of conventional (A1) milk as determinants of risk factors for heart disease, for example increasing cholesterol levels in the blood. While such observations were demonstrated in some preliminary studies in experimental animals, even those initial results were questioned and the findings were never able to be duplicated in large studies in humans, undertaken by independent investigators.

* The medical and scientific literature contains many examples of potential "magic bullets" which have been proposed as causes or cures of human disease. While Professor Woodford does not claim that conventional milk is the cause of heart disease, type 1 diabetes, autism, schizophrenia and some other conditions, he does suggest that a substance beta-casomorphin-7 (BCM7), which he describes as the "milk devil", generated from A1 milk, might be an important determinant of a vast array of causes of human ill-health. The small amount of research to date has not been on humans or human populations but is "animal work". Extrapolation to human populations needs to be done with care. We do not believe that present limited and inconsistent evidence justifies a conclusion which implies that only A2 milk (which does not generate BCM7) should be consumed, though further research would be of interest.

While A2 milk is perfectly acceptable, there are insufficient supplies worldwide to permit a global exchange of A2 for A1 milk. Milk and dairy products are enormously important food sources for children and adults. They provide valuable sources of essential nutrients. Indeed, it is impossible in a diet based on conventional foods to obtain adequate intakes of calcium if milk and dairy products are not consumed. Calcium is essential for healthy bone development and many other functions of the human body. Milk and water – rather than sugary beverages – are recommended to help reduce the global epidemic of childhood obesity and milk particularly enhances the nutritional quality of the diets of children.

It is an important responsibility of independent scientists to evaluate evidence relating to modifiably determinants of ill health, but it is equally important not to offer comment or advice which may have more adverse public health outcomes than benefits. This would seem to be the case with regard to the A1 – A2 saga. Alarm resulting from unproven health risks leading to reduction or elimination of milk and dairy products could lead to profoundly adverse health outcomes.

We need to be open to the results of further research, but as nutritional scientists with no conflict of interests, we find, given the present totality of evidence, no justification for the suggestion that intake of conventional milk and dairy products should be restricted. We would continue to encourage the use of reduced fat varieties for most people (other than for young children) in order to reduce intake of saturated fat and excess calories.

Professors Jim Mann and Murray Skeaff and Associate Professor Winsome Parnell
Department of Human Nutrition, University of Otago

ENDS

© Scoop Media