In 1993, Bob Elliott, eminent scientist and emeritus Auckland paediatric professor, made an intriguing observation.
After Samoan children migrated to New Zealand, their incidence of type-1 diabetes (T1DM) increased ten-fold. His suspicion of a dietary cause was heightened when he established that in their home country Samoan children mostly didn’t drink milk.
With scientific colleague Murray Laugeson, Elliott then discovered a strong correlation in 19 advanced nations between the rates of milk consumption and not only T1DM but also heart attack mortality.
Bovine milk contains 13%-15% solids as sugar (lactose), fat (66% saturated) and protein. This protein consists of soluble whey, and insoluble casein. Casein is further subdivided into alpha, beta and kappa chains.
Suspecting the role of casein, Elliott quizzed dairy scientist Jeremy Hill. As T1DM is an auto-immune disease, Elliott wondered if casein may be triggering this, as casein is known to release an immune reactive protein.
Hill suggested that Elliott focus on beta casein but thought its role unlikely.
Beta casein has two forms: A1 and A2. Each is a chain of 209 amino acids, but there is one tiny difference.
At position 67, in A1, the amino acid is histidine, whereas in A2 it is proline. As histidine forms a weaker bond, A1 betacasein fractures at that point and releases a fragment containing seven amino acids.
Entry into the bloodstream from the gut is facilitated if the gut is "leaky". This is the case with neonates to permit the absorption of colostrum.
As the seven-amino acid fragment behaves as an opioid, it is named beta casein morphin7, "BCM7". These opioid properties can be blocked by administering the opioid antagonist naloxone.
There is speculation that the opioid properties of A1 milk, render calves docile, so are less likely to be culled, selecting in favour of A1 milk.
Almost all mammalian milk, including human milk contains A2 with no A1 beta casein. About 8000 years ago, a mutation occurred and A1 milk is now produced by northern European Freisian and Holstein cow breeds. Jersey cows produce A2 milk.
Experiments with rodents confirmed that when fed A1 beta casein, they had a significantly greater tendency to develop T1DM than when fed A2.
Using rabbits, as they metabolise cholesterol in a similar way to humans, experiments revealed that those fed A1 beta casein developed atheroma significantly more readily than those fed A2.
Historically, before effective medications were developed to treat peptic ulcer, the treatment was the milk based "sippy diet". This treatment was accompanied by a sixfold increased death rate from heart attack in the United States and by 2.5x in the United Kingdom.
Mechanisms whereby BCM7 can cause coronary artery and T1DM disease are established.
BCM7, described by emeritus professor of agribusiness Keith Woodford as the "milk devil" also acts as an oxidant. When LDL cholesterol is oxidised, it becomes more adherent to arterial lining, potentially initiating atheroma.
BCM7 has a four-amino acid sequence identical to "GLUT 2", the glucose transporting molecule inside the insulin producing cells in the pancreas. An inflammatory response to BCM7, by cross reaction, may damage the GLUT 2 molecule and thus insulin production.
Prof Boyd Swinburne opined "changing dairy herds to more A2-producing cows may significantly improve public health if the A1/A2 hypothesis is proved correct and is highly unlikely to do harm".
In some Asian countries such as South Korea, the dairy herd is being converted to A2 milk production.
New Zealand’s Livestock Improvement Corporation has deleted from its breeding bulls those carrying two copies of the A1 gene and is discriminating against those with a single copy of the A1 gene.
New Zealand and Australian standard milk now contains much lower levels of A1 betacasein than other Western countries and in Australia A2 milk is widely available.
The notion that the proof of the benefits of A2 milk requires the gold standard of a double-blind trial is quixotic, just as it was not required to demonstrate the perils of smoking.
The essentially painless wholesale conversion to A2 milk has potential health benefits for hundreds of millions worldwide and can give NZ Inc a competitive advantage.
To return to the original question, is milk a health food or a health risk?
The answer is both. But now, because of the work of scientists, including Keith Woodford, consumers can choose either.
— Ian Breeze is a retired surgeon living in Dunedin.
