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msnbc.com
updated 8/25/2006 10:46:28 AM ET 2006-08-25T14:46:28

Demand for organic milk, which can sell for up to double the cost of other milk, is booming. Deciding whether to spend the extra money is not as clear-cut a decision as some suggest.

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People may turn to organic milk for health benefits, or environmental and animal rights’ issues. But when evaluating the health claims, so far, research does not support a health advantage of organic over conventional milk for any segment of the population.

That's because the U.S. Department of Agriculture has four requirements to define milk as organic, and confusion abounds about each.

Milk that is labeled “USDA Organic” must come from cows that have not been treated with bovine growth hormone (BGH) to increase milk production. People who focus on this goal express concern that hormones in milk could raise the risk of hormone-related cancers, or lead to higher levels of an insulin-like growth factor (IGF-1) linked with cancer.

But BGH is a protein hormone, which means that if any does appear in milk, enzymes and acid in our digestive tract destroy it. Dale Bauman, a professor of animal science at Cornell University, emphasizes that if IGF-1 is slightly higher in milk from BGH-treated cows, it represents a tiny fraction of the IGF we all produce each day. Bauman reports that we would have to drink 95 quarts of milk to equal the IGF-1 we make daily in our saliva and other digestive tract secretions.

We need to differentiate between levels of IGF in our blood, which some studies link to a possible increase in cancer risk, and levels of IGF in our food. Several organic-related Web sites refer to a study in which vegans (who eat no animal products) showed 13 percent lower IGF than non-vegans. But, a closer look at that study shows that milk consumption was not related to blood levels of IGF. Research shows high blood levels of IGF are linked with overweight, lack of exercise, and diets too high in saturated fat, refined carbohydrates or total calories.

No antibiotics
A second characteristic of organic milk is that these cows are not treated with antibiotics. If a cow in an organic herd does need to be treated with antibiotics, she is not returned to the herd for a period of 12 months. Yet in conventional herds, milk from cows that receive antibiotics is not used until tests show it is antibiotic-free. Tanks of milk are routinely tested to ensure no antibiotic content.

A third requirement of organic milk is that cows’ feed is grown without pesticides, whether the feed is grass or grain. Recent USDA reports show that nonorganic milk may contain low levels of certain pesticides, but these are far below established tolerance levels. Using organic feed may support sustainable farming practices, yet research has not found it affects the nutritional value of the cows’ milk.

Grazing time?
The final requirement for organic milk is that cows must have “access to pasture.” Many consumers assume this means cows graze in fields most of the year. But, the current standard does not require a specific length of time in pasture. A cow can graze in pasture only a limited time and still produce milk that is certified organic.

On the question of grain- versus grass-fed cows, some suggest that pasture-fed cows may produce milk that contains more conjugated linoleic acid (CLA), a special type of fat that may protect against cancer and other health problems. But Michael Pariza, professor of food microbiology and toxicology at the University of Wisconsin, and a leading expert on CLA in dairy products, says grass feeding by itself does not assure increased CLA. He and Bauman both note that cows fed mixed grains with soybeans or other additions can produce milk that has higher CLA levels than milk from grass-fed cows. This may lead you to spend less on milk and more on fruits, vegetables, whole grains, fish and other healthful foods.

Nutrition Notes is provided by the American Institute for Cancer Research in Washington, D.C.

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