Eat Dairy Foods, Avoid Breast Cancer?
Study: High-Dairy Diets Linked to Less Risk of Postmenopausal Breast Cancer
Dec. 14, 2005 -- Postmenopausal women who eat lots of dairy products may be
less likely to develop breast cancer.
Don't skip over the word "may" in that sentence. It's too soon to
declare dairy as protector against breast cancer, the researchers caution.
The study comes from the American Cancer Society's Marjorie McCullough, ScD,
RD, and colleagues. It appears in Cancer Epidemiology, Biomarkers, and
Women's Diets Studied
McCullough's study included more than 68,000 women, most of whom were white
and middle class.
All of the women had completed menopause and didn't have breast cancer when
the study started in the early 1990s.
They completed lengthy surveys about their diets and lifestyles. The surveys
covered consumption of 68 foods including milk, cheese, yogurt, ice cream, and
other dairy products. Most of the dairy products consumed were low fat.
Use of multivitamins and calcium supplements were also noted.
More Dairy Foods, Less Breast Cancer
The women were followed through August 2001. By then, they had had 2,855
cases of breast cancer.
Women who had the highest dietary calcium intake were 20% less likely to
have been diagnosed with breast cancer than those whose diets were lowest in
Calcium isn't only found in dairy products. However, dairy products were the
biggest calcium source for women in McCullough's study.
No Link Seen With Supplements
The finding focused on calcium in foods. Use of calcium supplements weren't
linked to a lower risk of breast cancer.
Vitamin D, which is also present in dairy foods, wasn't linked with an
overall lower risk of breast cancer.
Blood vitamin D levels in people are made up from dietary sources and also
from exposure to sunshine. Since levels in the blood were not measured in this
study, they only looked at the relationship of breast cancer to the dietary
intake of the vitamin.
Other studies cited in this article have suggested that higher levels of
vitamin D may lower the risk of breast cancer.
Small Drop in Risk
McCullough is a senior epidemiologist in the American Cancer Society's
Epidemiology & Surveillance Research department.
"Our findings suggests that dairy products, composed mainly of low-fat
sources, or some component within these foods are associated with a small but
significantly lower risk of breast cancer in postmenopausal women,"
McCullough says, in a news release.
Her study states that dairy products contain elements that may have
anticancer effects, such as calcium and vitamin D. On the other hand, the study
cites that hormones and growth factors found in dairy products may raise the
risk of some cancers.
"Thus, the net effect of dairy product consumption on breast cancer risk
may reflect a balance of beneficial and detrimental factors," the
No Recommendations Made
"More study is needed before we can make concrete recommendations,"
McCullough says. She notes that the reason for the lower risk of breast cancer
The study shows that women who had the highest intake of dietary calcium
also tended to smoke less, be more physically active, take menopausal hormone
therapy and multivitamins, be leaner, have gained less weight since age 18, and
consume less fat and alcohol. Those women, though, did not have a different
menstrual or pregnancy history compared with the group with the lower intake of
"While we controlled to the best of our ability for other possible
explanations, it's certainly possible women who consume low-fat dairy products
have other health-related behaviors that could also lower the risk,"
The study doesn't show whether the women had favored or avoided calcium
throughout their lives.