Diabetes
The controversy which is the focus of this article all began back in 1993 when Professor Bob Elliott - a diabetes researcher at Auckland University in New Zealand became interested in the wide disparity in the rates of type 1 diabetes around the world. The incidence of the disease varies enormously. He initially observed that the incidence in Samoan children in New Zealand was dramatically higher (10 fold) than that occurring in their home islands. He also knew that casein - a protein present in milk was a diabetogenic agent in lab rats.

If milk is a cause of type 1 diabetes the disease ought to be very prevalent in societies where a lot of milk is drunk. The obvious focus would be the Masai people of Kenya who consume very large quantities. The problem is that they do not seem to get type 1 diabetes. Professor Elliott decided to ask New Zealand milk scientists whether the milk drunk in Kenya was in any way different from that drunk here in New Zealand. The scientists revealed that there was a difference in a protein component of the Masai milk which involved the structure of the casein molecules. That type of milk is now designated A2, while the variety commonly consumed in New Zealand is designated A1. (Milk is made up of carbohydrates, fats and proteins. The precise nature of the protein content is determined by the genetic makeup of the animal producing the milk. Milk protein is made up of approximately 5% whey protein and 21% casein protein. It is the nature of the casein which can vary among different animals, breeds and species.)

These observations lead to epidemiological and lab research. The most significant epidemiological study was published in 2003 in the NZ Medical Journal. (1) It examined the relationship between type 1 diabetes, ischaemic heart disease and cows' milk containing A1 beta casein - the type of milk commonly available in New Zealand and many other western countries. The twenty-country study reported very high correlations between A1 milk casein consumption and type 1 diabetes - in the order of 0.92 - a remarkable association in the biological field. There was a 300-fold variation in the incidence of type 1 diabetes in the countries involved which is notable in itself!

Other research at the University of Iceland has compared milk consumption in Iceland with that of other Scandinavian countries. Most Icelandic milk comes from A2-producing cows and the incidence of Type 1 diabetes there is substantially lower than the other northern countries. Milk in Iceland comes from an ancient Norse breed of cow, which produces A2 milk. The studies have confirmed that Icelandic milk is indeed low in beta casein A1 (2) and also that consumption of milk is much higher in Iceland than the other Scandinavian countries.(3) This suggests that the nature of milk may be a risk factor for type 1 diabetes.

Further Evidence
Professor Elliott also conducted studies in which he gave rats susceptible to diabetes, the suspect A1 milk product, which contains a protein fragment now designated BCM-7, and casein derived from A2 milk which does not contain the protein in question. Sure enough none of the mice fed the A2 diet developed diabetes while 47% of those fed regular milk succumbed to the disease. (4)

Research by Boales and associates published in 2002 (5), involving rats and mice, only weakly support Professor Elliott's earlier work. It has, up until recently, formed the main rebuttal to his findings. It has now been revealed however that the feed used in that study was incorrectly formulated and the milk, supposedly free of the A1 protein, was contaminated with the key casein protein from A1 milk. Unfortunately it has now been alleged that those associated with the study failed to make this information public; indeed, that they may have deliberately withheld the information - thus leading to intense controversy in New Zealand over the role of Fonterra, New Zealand's major milk export corporation.

Heart Disease
In 2001 the link between A1 milk consumption and heart disease was explored by Corran McLachan who was startled to note the links between diabetes incidence and that of heart disease. He established a correlation of 0.86 between A1 casein consumption and ischaemic heart disease in a group of countries.(6)

A University of Queensland study in 2003 determined that rabbits fed A1 milk developed arterial plaque while those fed A2 milk did not (7). Note: There is also some evidence that the responsible component in A1 milk may lead to oxidation of LDL cholesterol.

Research by the Elliott group has found that A1 beta casein per capita consumption in the milk and cream supply was significantly and positively correlated with IHD (ischaemic heart disease) in 20 affluent countries. The study used a five-year time lag, over a 20-year period – thus providing an alternative hypothesis to explain the high IHD mortality rates in northern compared to those of southern Europe. In Crete for example where heart disease is the lowest in Europe, the locals drink only small amounts of milk, about 40% of which is reported to be from sheep and goats who do not produce A1 casein. In 1995, A1 milk per capita intake varied greatly among many countries, from about 0.3 g/day in Guernsey, to 3.0 g/day in Finland. (Consumption is even lower in Japan). Comparison has also been drawn between Ireland and France. The French have much lower heart attack rates in spite of similar total fat consumption levels. The research concluded that the Irish/French IHD rate of 3.8:1 was in line with the milk protein type ratios (total milk protein per capita ratio 3.1:1; A1 per capita ratio 4.1:1) Overall it was noted that countries with the highest IHD rates all consume more than 2 grams of A1 milk per capita per day in their diet.

Other Diseases
It has been shown that BCM-7, the key casein peptide in A1 milk, is biologically active (beta casein A2 cannot give rise to BCM-7), exhibiting amongst other things opiate-like properties. Independent research has also shown rats injected with BCM-7 exhibit symptoms similar to schizophrenia. BCM-7 has been shown to affect factors involved in heart disease, such as platelet aggregation and LDL oxidation.

A potential link between milk consumption and autism was postulated many years ago. A University of Florida researcher Robert Cade reported in 1999 that beta-casomorphin-7 is found in high concentrations in the blood and urine of patients with either schizophrenia or autism. It is believed that in some children fragments of casein can leak through the gut wall into the blood, and from there into the brain causing significant behavioural problems. A2 Corporation, a NZ company involved in the testing and production of A2 milk, say that comments on the University of Florida website have stated that preliminary research findings have shown that 95% of autistic children have 100 times the normal level of milk protein in their blood. They go on to state that at least 8 out of 10 patients no longer had symptoms of autism or schizophrenia when put on a milk- free diet. Unfortunately the work does not appear to have been published to date and thus cannot be scientifically assessed.

How could some milk be much safer than others?
Milk is regarded by many as a natural food with many beneficial nutrients. How could it cause disease? The supporters of the A2 hypothesis believe that some thousands of years ago a natural mutation occurred in a few cows, which resulted in a change in a protein molecule in their milk. That molecule beta-casomorphin-7 (BCM-7) is the result of a variant of the casein molecule in which histidine is substituted for proline at one point in its structure. This interpretation does not appear to be in dispute.

It is however unclear how we have arrived at a situation today where some breeds produce the original milk and others produce A1 milk which by definition is now the most common variety in many parts of the western world.

How could a molecular change in a component of milk lead to disastrous results for human health?
The concept of "cross-reactivity" between antigens in cows' milk and antigens on the pancreatic ß-cell is appealing and has been proposed by several investigators. More recently, a more elaborate potential mechanism has been proposed. It is hypothesized that the BCM-7 cleaved from A1 beta-casein, has opioid characteristics which suppress the body's immune surveillance, or responses, to antigenic agents such as enteroviruses or endogenous retroviruses which then damage the pancreatic ß-cells. It is reported that it takes 10 times as much naloxone, an opioid antagonist, to counteract BCM-7 as it does to suppress morphine. (Information from Bob Elliott's 1993 rat studies in which animals consuming A1 milk products and given naloxone, also failed to develop diabetes.)

A2 researchers also believe that gut permeability in some individuals, particularly young children, leads to abnormal protein ingestion into the blood and probably the brain. It has been shown that type 1 diabetics have specifically higher levels of antibodies to A1 beta casein than non-diabetics.

Health Friendly Cows
Is your cow's milk healthy? If you have one in your back yard you could use the A2 Corporation's test kit to alleviate your fears. I suspect that this may not be an option for most readers!

The mutation, which occurred in cows in the past, has lead to a situation in which some breeds of cows appear to have changed little and still produce purely A2 milk. Examples are native Icelandic cows, Jersey and Guernsey animals together with many French cows. Asian and African cows and other milk producing species like camels and goats all produce A2 milk. In Western countries dairy herds are a genetic mixture. Thus in New Zealand approximately one third of animals produce A2 milk, one third produce A1 milk and the rest produce a mixture. The A2 Corporation produces these testing kits so that individual animals from mixed producing breeds like Red Danish, Holstein/Friesian and Ayrshires can be assessed to determine what type of milk individual animals produce. It is thus possible to create herds producing the desired type of milk. In New Zealand it has been estimated that in ideal circumstances the entire national dairy herd could be converted to A2 production in eight years.

A2 milk is available in supermarkets and health shops in New Zealand and Australia. Over 1000 US health stores are now reported to stock it. In New Zealand A2 milk is only guaranteed to contain 95% A2 beta casein.

Feeding Infants and Young Children
Cow's milk contains up to 3 grams per 100 ml of casein. Opponents of cow's milk consumption say that the problem with it is not simply its casein content - that's the part that may produce the casomorphin opiates. The nutrient "package" in milk - loads of sugar (lactose), animal protein and fats, can trigger the production of pro-inflammatory IGF-I in the body, and that may be the reason it is linked to a variety of diseases.

The milk of cows varies from that of humans in a large number of ways. The minerals sodium, potassium, calcium, magnesium and chloride are present in much larger quantities in cow's milk. Carbohydrate levels are also much higher (notably lactose). The most dramatic difference however lies in the casein content. Human milk contains very little. (It is also rich in whey protein of a different type to that present in the cow.)

The possible role of A1 milk in precipitating type 1 diabetes in susceptible children, and possibly laying the foundations for heart disease and other diseases in later life, creates some problems for prudent new parents. There doesn't appear to be any A2 baby milk food products currently available. (Some studies have identified high levels of BCM-7 in infant formulas.) No doubt A2- derived formulas will become available in the foreseeable future. Until they become available, it may be prudent for new mothers to breast-feed for as long as practicable. Some believe that the digestive and immune systems of infants may be better able to tolerate A1 milk products as they grow older.

Until there are more answers, it seems that a prudent approach, regarding the consumption of regular A1 milk products, should be applied to babies and young children. Those who are not breast-fed might consume A2-based products, including goat's milk, if available. Failing that they could consume baby formulas containing only whey protein, thus avoiding the possible offending casein derivative of A1 milk.

Adult Milk Products
There is some good news for concerned adults. Butter contains negligible amounts of protein, and beta casein is degraded during cheese making, so A1 milk can be safely used in the production of cheeses. It is not currently known whether yogurts derived from A1 milk are devoid of BCM-7. The role of pasteurization in providing protection from BCM-7 is controversial and a complex technical subject. It is discussed in Keith Woodford's book. The fascinating possibility that pasteurization methods common in the earlier part of the 20th century may have favoured the retention of BCM-7 and thus encouraged heart disease, is discussed in Woodford's book.

Speculations
The A2 hypothesis alleges that consumption of regular milk may lead to a wide variety of diseases. The A1 disease list includes type 1 diabetes, MS, autism, other neurological conditions and cardiovascular disease. Health science is now presented with a serious challenge. The possible association between milk consumption and a wide variety of human diseases will require specific studies designed to address possible associations on a case-specific basis. Unfortunately A2 milk has not hit the worldwide health radar to date.

Red wine has now become a health imperative believed to be responsible for the French cardiovascular advantage. What if the real advantage was A2 milk drunk by the French and few others? As a result of the unresolved controversy the author is hedging his bets and drinking A2 milk plus a glass or two of red wine daily!

The extensive publicity surrounding the A2 (or is it A1) issue here in New Zealand has lead to the government announcing an investigation into the safety of A1 milk. Subsequent to that it has now been announced that the investigation will not proceed as the European Food Safety Authority is taking over the investigations. Hopefully the regulatory authorities in Canada and the US will finally become aware of the issues involved. Until that happens the onus lies with the educated consumer. Will we eventually see health warnings on regular A1 milk? I suspect that the A2 Corporation hopes so.

Readers who would like to explore this fascinating controversy further are recommended to read "Devil in the Milk" by Keith Woodford Craig Potton Publishing Nelson New Zealand ISBN 978-1-877333-70-5

References

1. Elliott et al. Ischaemic heart disease, type 1 diabetes and cow's milk A1 beta-casein NZ Med J 2003:116-1168
2. Thorsdottir I et al. Pediatrics. 2000 Oct; 106(4): 719-24
3. Diabetes Nutr Metab. 2002 Aug;15(4):240-5.
4. Elliott et al. 1997 The role of beta casein variants in the induction of insulin-dependent diabetes in the non-obese diabetic mouse and humans. In; Milk Protein Polymorphism (special issue) 9702:445- 453 Brussels International Dairy Federation.
5. Boales et al. A multi-centre, blinded international trial of the effect of A1 and A2 beta casein variants on diabetes incidence in two rodent models of spontaneous type 1 diabetes. Diabetologica 2002: 45: 1240-1246
6. McLachan CNS Beta-casein A1, ischaemic heart disease mortality and other illnesses. Medical Hypotheses 2001 56: 262-272
7. Campbell J. A casein variant in cow's milk is atherogenic. Atherosclerosis 2003:170(1) 13-19