An emerging body of research suggests that many of the 1 in 4 Americans who exhibit symptoms of lactose intolerance could instead be unable to digest A1, a protein most often found in milk from the high-producing Holstein cows favored by American and some European industrial dairies. The A1 protein is much less prevalent in milk from Jersey, Guernsey, and most Asian and African cow breeds, where, instead, the A2 protein predominates.

"We've got a huge amount of observational evidence that a lot of people can digest the A2 but not the A1," says Keith Woodford, a professor of farm management and agribusiness at New Zealand's Lincoln University who wrote the 2007 book Devil in the Milk: Illness, Health, and the Politics of A1 and A2 Milk. "More than 100 studies suggest links between the A1 protein and a whole range of health conditions"¡ªeverything from heart disease to diabetes to autism, Woodford says, though the evidence is far from conclusive.

...The difference between A1 and A2 proteins is subtle: They are different forms of beta-casein, a part of the curds (i.e., milk solids ) that make up about 30 percent of the protein content in milk. The A2 variety of beta-casein mutated into the A1 version several thousand years ago in some European dairy herds. Two genes code for beta-casein, so modern cows can either be purely A2, A1/A2 hybrids, or purely A1... The A1 milk hypothesis was devised in 1993 by Bob Elliott, a professor of child health research at the University of Auckland. Elliott believed that consumption of A1 milk could account for the unusually high incidence of type-1 diabetes among Samoan children growing up in New Zealand. He and a colleague, Corran McLachlan, later compared the per capita consumption of A1 milk to the prevalence of diabetes and heart disease in 20 countries and came up with strong correlations.

Lincoln University agribusiness professor Keith Woodford has documented the murky corporate games, favouritism and wild spin-doctoring that were rife once A2 milk took its first tentative steps into the New Zealand market. His book, Devil in the Milk, showed how the New Zealand Food Safety Authority (NZFSA) had misrepresented the science and deceived the public as the debate on milk types heated up... It was subsequently revealed by the New Zealand media that the NZFSA accepted advice and lobbying from dairy giant Fonterra during the review process.

It was too late for A2, and the product never took off in its home country. The company's management decided to enter the Australian market and leave the politics and lobbying of New Zealand behind them.

Unfortunately, Dairy Australia also engaged in questionable tactics during A2's early days. Fact sheets written by Dairy Australia nutritionists in 2007, just as A2 was launching, were published on its website. The sheets quoted research by Sydney academic Stewart Truswell saying there was no convincing evidence that the A1 protein had adverse effects on humans. Truswell later admitted he had been paid by Fonterra as an expert on the A1-A2 issue.