By David Barber
Parents in many parts of the world have long urged their children: "Drink up your milk. It's good for you." But is it?
New research has raised doubts in New Zealand, one of the world's biggest milk producers and responsible for about one-third of all the dairy products traded over international borders.
A study involving 20 countries published in the New Zealand Medical Journal found a significant link between drinking milk containing the A-1 beta case in protein and the national rate of heart disease and insulin-dependent diabetes.
Researcher Dr Murray Laugesen said populations that consumed a lot of A-1 milk had a higher rate of heart disease than countries whose cows produced milk containing the alternative A-2 protein.
There was also a significant correlation between the A-1 milk consumption and childhood diabetes that required treatment with insulin, he said.
But Dr Laugesen and fellow researcher Professor Bob Elliott said their two-year study did not prove the A-1 protein, which was dominant in the milk New Zealanders drink every day, actually caused heart disease or diabetes, but showed that further research was needed.
They said that Guernsey, in the Channel Islands, where cow's milk had virtually no A-1 protein, had the third lowest rate of heart disease, behind Japan and France, where the cows also had less A-1.
New Zealand's Food Safety Authority (NZFSA) and ministry of health immediately issued a joint statement which said the results were inconclusive and no reason for people to stop drinking milk.
Dr Bob Boyd, the NZFSA's principal public health advisor, called the study an "important contribution to further research", but said people concerned about heart disease should get more exercise, quit smoking and cut down saturated fats in their diet rather than give up milk.
This message was reiterated in an editorial in the journal written by Professor Robert Beaglehole of the World Health Organisation, and Professor Rod Jackson of the Auckland Medical School, who also called for more research.
The researchers admitted a vested interest in their project, both being directors of the New Zealand Milk Institute, which owns a patent related to the production of milk free of the A-1 protein.
They also received a grant for their study from a company called the A2 Corporation, which wants to process and distribute A2 milk but claims the mega Fonterra Cooperative Group, which controls about 96 percent of all milk produced in New Zealand, is blocking it.
The A2 Corporation has filed a lawsuit against Fonterra, claiming it is suppressing critical research on the issue, while the mega co-op insists there is no proof A-1 milk is bad for you.
The debate is being anxiously followed by the government and economists in New Zealand, a trading nation where dairying accounts for 20 percent of total exports and seven percent of the country's entire gross domestic product. - Sapa-DPA