NZ keen to drink from British milk research

By PHILIPPA STEVENSON agricultural editor

Ground-breaking British research looks likely to give the New Zealand dairy industry the proof it needs to support health-giving claims for milk products.

Scientists from the Universities of Southampton and Reading have begun $2.4 million, three-year human trials seeking to establish whether drinking cows' milk can help to boost the body's immune system.

They will focus on conjugated linoleic acid (CLA), the naturally occurring fatty acid found in significant amounts only in foods produced from ruminants - milk, butter, cheese, lamb and beef.

The work follows successful American experiments, mainly on mice and rats, showing CLA was effective in fighting several types of cancer, atherosclerosis and diabetes. It also enhanced immune function and helped to control weight.

The British study has been welcomed in NZ as pastoral industries' chance to claim health benefits for products that have increasingly suffered a bad press.

Dr Robert Norris, of New Zealand's Dairy Research Institute, said the industry was excited by the possibility that British science would finally prove milk's beneficial effect on humans. The beef and sheep industries could also benefit.

"This is good news for all pastoral farming, really."

Diet can influence the levels of CLA deposited in the fat tissues and milk of cattle and sheep, and United States research has shown that levels can be nearly four times higher in milk from cows grazing pasture.

Dr Norris said the institute had surveyed butter bought in British supermarkets and found that product from this country and Ireland, which also raises cattle on a mainly pasture diet, had CLA levels higher than other countries.

"Typically the concentration of CLA in New Zealand milk fat is as much as double that from Danish or American cows," he said.

New Zealand could ill afford the kind of trials being conducted in Britain, but had kept a watching brief on overseas science while doing limited laboratory studies on mice.

"[CLA] has a wide range of activity, of which much has been substantiated in animal studies, but this is one of the first major human clinical studies.

"We are hoping to come out quickly in the event of a favourable research finding with [a recommendation] to buy New Zealand butter and cheese because it has a high CLA content."

The project leader of the British research team, Dr Philip Calder, told a web-based news service that CLA might protect against cancer because it improved the immune system's ability to seek out and destroy tumours.

"We will be testing two different forms of CLA, which we believe are the most important, giving people three increasing doses over a six-month period to find the type and dose that produces health benefits," he said.

The study has been funded by Britain's Milk Development Council and the Biotechnology and Biological Sciences Research Council and it is hoped that if the health benefits of CLA are proven, it could lead to a new range of functional dairy products.

CLA was first isolated and identified more than a decade ago by food scientist Michael Pariza, director of the Food Research Institute at the University of Wisconsin-Madison, while looking for something in cooked hamburger that prevented skin cancer in mice.

Last year, the institute presented the first results from human studies which showed that CLA in the form of a widely used dietary supplement might help overweight adults lose weight and fat, maintain weight loss and retain lean muscle mass.

The results indicated that overweight people who took CLA had less trouble staying on a diet, regained less fat when they stopped and retained more muscle mass. Other research showed that adult diabetics taking CLA had improved insulin levels.

CLA is produced in an animal's rumen, or stomach, when certain rumen bacteria change the structure, or conjugation, of free linoleic acid contained in feeds and forages.

Fish, pork and seafood are not significant sources of CLA, and fruits, vegetables and other foods, excluding vegetable oils, contain little or none.

Figures from the US show that Colby cheese had the highest concentration of CLA, with 6.1mg per gram of fat, closely followed by ricotta cheese and lamb with 5.6mg.

Homogenised milk had 5.5mg, mozzarella cheese 4.9mg, butter 4.7mg, plain yoghurt 4.8mg, sour cream 4.6mg and cottage cheese 4.5mg.