THURSDAY, March 14, 2013 — Though some say milk does a body good, more research in recent years has found a link between a dairy-rich diet and the effect on women's health, especially cancer.
The newest study in a growing body of research just published in the Journal of the National Cancer Institute, reports that women with early-stage invasive breast cancer who consumed one or more servings of high-fat dairy foods were more likely to experience a recurrence of the disease than women who ate a low-fat dairy diet. The study found that women who consumed a diet rich in high-fat dairy had a 49 percent increased risk of dying from breast cancer, and also a 64 percent higher risk of dying from any health cause, primarily cardiovascular disease.
"We found the elevated risk specifically with high-fat dairy," said Candyce Kroenke, ScD, MPH, a staff scientist at Kaiser Permanente and lead author on the study.
We found the association with saturated fat with the breast cancer outcome was weaker, suggesting it’s not just saturated fat but specifically fat found in dairy."
And it isn't just the dairy you drink, said Kroenke. High-fat foods such as cheese, butter, yogurt, ice cream, and desserts may also pose certain health risks. She said food produced with today's dairy supply tend to have elevated estrogen levels. Dairy foods that are higher in fat have high levels of estrogen than low-fat dairy products.
Many researchers have found a link between overexposure to estrogen and breast cancer, particularly estrogen receptor positive breast cancer, which is the most commonly diagnosed form of the disease.
"In western countries they manage to breed cows and modify them so they can be pregnant at the same time and give milk, which means the milk has more estrogen," explained Kroenke. "It’s this particular method of production that leads to the level of hormones we’re talking about in the study."
The study looked at 1,893 patients who had been diagnosed with early-stage invasive breast cancer between 1997 and 2000. The subjects, pooled from Kaiser Permanente's Northern California region and Utah's cancer registry, entered the study two years after their initial diagnosis. The women completed questionnaires about their diet, and 1,513 filled out a follow-up questionnaire six years later, which addressed the types and quantity of milk products they consumed on a regular basis. Among the entire group of women, 349 had a recurrence of breast cancer and 372 died in the decade after their diagnosis. Breast cancer was the cause of 189 of the women's deaths.
Even still, many experts say overall data on breast cancer and dairy consumption is inconclusive. Alice Bender, a registered dietitian at the American Institute for Cancer Research, a nonprofit that examines the links between diet, exercises, and cancer prevention, believes the evidence in the study isn't strong enough. "Some studies actually show protection with diary and some show higher risk," she noted. "We do recommend that if you have dairy, you do go with the lower fat versions. If you eat a lot of cheese, every bite you take is a lot of calories compared to a bite of carrot or apple."
Some women with breast cancer are even afraid to go the milk substitute route, since there's some research that suggests soy milk can put women at risk for breast cancer. But Bender said these studies have largely been done on animals. "Animals metabolize differently and it doesn’t effect humans in the same way," she says."The latest evidence is pretty clear that there’s not a link between soy and breast cancer risk. That is something that women do not need to worry about." She says the dangers with these products may be in the added salt and sugar.
Bender says women with breast cancer don't necessarily need to go completely vegetarian or vegan, but they will benefit from cutting out some meat in their diet. "Look at your plate and try to fill at least two-thirds of your plate with plants — at least," said Bender, since even a larger body of evidence finds fruits and vegetables are cancer-busting foods.
Kathy-Ellen Kups, a breast cancer survivor who has been cancer-free since 2004, has continued to consume dairy. "I've always been concerned about bone health, especially after chemotherapy," she said, since calcium is one of the best ways to fend off osteoporosis. But she did alter her diet in other ways when she was diagnosed with breast cancer. She eliminated red meat and read labels to stay away from processed foods and nitrates. Kups recommends having low-fat dairy, as the study suggests.