Grabbing a bottle of milk from the supermarket was once a simple task; now the chillers seem to be lined with endless options of white bottles decorated with brightly coloured tops. Full cream, light, trim, organic, calcium enriched and zero-lactose choices line the shelves, and now there is a new milk in town. A2 milk is popping up in our stores, bringing with it some serious health benefit claims, but what's actually in our milk and how does A2 differ?
Cows' milk is around 87 per cent water and 13 per cent solids comprising fat, lactose, minerals and protein. Milk proteins are mostly casein, of which 30 to 35 per cent are beta-casein, which come in A1 and A2 forms. The variations differ by a specific amino acid with A2 milk having proline at position 67 in the protein chain, whereas A1 milk has histidine in that position. Originally all milk is thought to have been A2 milk, until thousands of years ago a genetic mutation in European cattle occurred, resulting in the A1 variation.
Standard milk contains a mix of A1 and A2 beta-caseins, whereas A2 labelled milk has only the A2 form. When we drink standard milk, the histidine breaks down into a protein fragment called beta-casomorphin-7 (BCM7) that has been linked to type 1 diabetes, heart disease and autism. There are suggestions that people with a susceptibility to these diseases should avoid normal milk and instead drink the proline-containing A2 milk, which doesn't produce BCM7. Others who suffer from lactose intolerance symptoms, including bloating, cramps and diarrhoea, have reported that their symptoms go away when they drink A2 milk. As BCM7 slows down the passage of food in the gut, allowing more time for lactose fermentation, the theory is that BCM7-free A2 milk moves lactose through quickly, reducing bacterial fermentation and possibly relieving digestive pain.
As a consumer, it's hard to know if paying the extra for A2 milk is worth it. Searching through the academic research came up mostly with small studies relating histidine in milk to diseases and digestive symptoms.
As part of the Government's National Science Challenges, the high-value nutrition programme has funded $1 million for research between AgResearch and the a2 Milk Company to carry out thorough local scientific research. Initial clinical studies indicated that the discomfort some people think is lactose intolerance may actually be A1-induced small intestinal inflammation, reduced when A2 milk is consumed instead. If the results prove conclusive, New Zealand-produced A2 milk could be marketed towards people who don't currently consume milk because of their intolerance symptoms, opening up a greater share of the rapidly growing export markets of China and Southeast Asia, which have a high incidence of perceived dairy intolerance.
