Two recent studies are souring milk's image among health authorities. One, published in the November issue of the American Journal of Clinical Nutrition, shows that women who consume two or more glasses of milk a day have twice the risk of a certain form of ovarian cancer than those who rarely or never consume milk.
Headed by Susanna Larsson at the Karolinska Institute in Sweden, researchers conducted a prospective study of more than 60,000 women and concluded that “intakes of lactose and dairy products, particularly milk, were significantly associated with the risk of serous ovarian cancer.” (Serous epithelial cancer is the most common type of ovarian cancer.)
The second study, presented last month at the North American Association for the Study of Obesity Conference, shows that high dairy consumption does not help dieters lose weight, refuting the findings of an earlier and smaller study that the dairy industry has aggressively publicized through major advertising campaigns, including a prominent one featuring talk show host Dr. Phil. The new study was conducted by Jean Harvey-Berino, Ph.D., a professor at the University of Vermont.
The original study—which had seemed to suggest that dairy products might help weight loss—had only 11 participants in the dairy group, and required a 500-calorie per day diet deficit. Its findings do not appear to hold, in light of the new study which used a similar method in a larger sample.
“Milk's biological purpose is to promote rapid growth in infant cows,” says Amy Joy Lanou, Ph.D. “It makes biological sense that its nutrients and hormonal effects might also promote the growth of cancer cells.”
As to the Harvey-Berino study, Dr. Lanou says, “It reminds us that the dairy industry's health claims are often based on thin scientific evidence.” Dr. Lanou's letter challenging the dairy industry's weight-loss claims is scheduled for publication in the January issue of Obesity Research.
The Swedish study is one of several published in the past few years suggesting a link between dairy consumption and ovarian cancer. The Iowa Women's Health Study of more than 29,000 postmenopausal women showed that the highest consumers of lactose (milk sugar) had a 60 percent increased risk of ovarian cancer as compared to those who consumed the least lactose.
In Harvard's Nurses' Health Study, each daily glass of low-fat or skim milk was associated with a 20 percent increase in serous ovarian cancers. Researchers hypothesize that galactose, a component of the milk sugar lactose, may damage ovarian cells, making them more susceptible to cancer.