Have we all been duped by the dairy industry’s slick, celebrity-driven "got milk?" advertising campaign?

Milk, the sacred cow of the American diet, is under attack, and not just by animal-rights activists. Though federal dietary guidelines and most mainstream nutrition experts recommend that people drink three glasses of milk a day, researchers are examining the role of dairy in everything from rising osteoporosis rates, Type 1 diabetes and heart disease to breast, prostate and ovarian cancer.

One fact is indisputable: Our bodies need the mineral calcium to build and maintain bones and teeth. Calcium also helps with blood clotting, muscle function and regulation of the heart’s rhythm. The debate centers on whether milk is really the best – or even a necessary – source. Ten thousand or so years ago, cow’s milk was not part of the human diet.

For consumers, the issue is profoundly confusing, especially when it comes to osteoporosis. On one hand, we’ve had it hammered home since grammar school that milk is a health food. We’re told that increasing calcium intake by drinking milk will prevent osteoporosis, the weakening of bones.

But researchers Walter Willett, chairman of the department of nutrition at the Harvard School of Public Health, and T. Colin Campbell, professor emeritus of nutritional biochemistry at Cornell University, say there is little evidence that shows boosting your calcium intake to the currently recommended levels will prevent fractures.

Willett, who co-authored The Nurses’ Health Studies, one of the largest investigations into the risk factors for major chronic diseases in women, found that women with the highest calcium consumption from dairy products actually had substantially more fractures than women who drank less milk.

Campbell, who like Willett comes from a dairy-farming family, found the same thing after spending several decades surveying health-related effects of a plant-based diet and death rates from cancer in more than 2,400 Chinese counties.

Both men say there is no calcium emergency; Americans get plenty. And they argue that the unnecessary focus on calcium prevents us from using strategies that really work in the fight against osteoporosis, including getting enough exercise and vitamin D and avoiding too much vitamin A.

"The higher the consumption of dairy, animal protein and calcium, the higher the fracture rate – an indisputable observation in my view," says Campbell, whose life work is compiled in The China Study, one of the most comprehensive nutritional studies undertaken.

The link between milk and cancers is sketchier – peer-reviewed studies back both pro- and anti-dairy viewpoints – though a growing body of evidence has shown that animal-based foods are associated with prostate cancer, possibly because of the high intake of calcium and phosphorus, Campbell said.

The dairy industry, the federal government and most conventional registered dietitians and nutritionists say just the opposite. Milk is more than just calcium; it’s a relatively cheap little package of fat, vitamins, proteins, carbohydrates and minerals.

Some research shows calcium may help protect against colon cancer and high blood pressure. A large-scale government study called DASH (Dietary Approaches to Stop Hypertension) found that a balanced, low-fat diet rich in fruits, vegetables and low-fat dairy foods may help reduce blood pressure as effectively as some medications.

The calcium from some vegetables such as broccoli, bok choy and kale is absorbed as well as or better than calcium from milk and milk products, according to the National Dairy Council’s Calcium Counseling Resource. But the report also says that to get the same amount of calcium absorbed from 1 cup of milk, one would have to eat nearly 2 1/2 cups of broccoli or 8 cups of spinach.

"The advantage of dairy is that it’s convenient, and children are more likely to consume it over broccoli and prunes," says Jeanette Newton Keith, a gastroenterologist at the University of Chicago. She advocates a whole-food diet and recommends dairy as part of the DASH plan.

Though dairy is high in saturated fat, the dairy industry claims that low-fat dairy products can encourage weight loss. During the last few years it has spent millions on a controversial "got milk?" advertising campaign.

In response, the Physicians Committee for Responsible Medicine (PCRM) filed false-labeling petitions last June with the Federal Trade Commission and the Food and Drug Administration. They maintain that the "got milk?" weight-loss ads are "dishonest," because scientific evidence contradicts the claims. The dairy industry based its assertion largely on the work of University of Tennessee researcher Michael Zemel, who received funding from the Dairy Council and who also has patented a weight-loss program using calcium.

© 2006, Chicago Tribune.

Distributed by Knight Ridder/Tribune Information Services.