A diet high in calcium and low in lactose may reduce the risk of ovarian cancer among African-American women, suggests a new study. Published in the British Journal of Cancer, the study adds to the limited research on lifestyle and ovarian cancer risk among African Americans.
Previous research investigating milk consumption and the ability to digest lactose and ovarian cancer risk has been inconsistent. The hypothesis is that the lactose component of dairy may increase the risk of ovarian cancer through its action on ovarian cells. These inconsistencies could relate to other anti-tumor compounds in dairy foods, especially calcium and vitamin D.
Yet most of this previous research is among women of European ancestry. With African Americans at higher risk of low vitamin D levels and many have trouble digesting lactose, it’s possible these factors do affect African American women, the authors hypothesized.
This study analyzed data among participants in a population-based case-control study of ovarian cancer in African-American women in 11 states. African-American women ages 20 to 79 with newly diagnosed ovarian cancer were compared to healthy, self-identified African-American women. The 490 women diagnosed with ovarian cancer and 656 control participants answered questions on the phone about how much dairy they consumed, how much time they spent in the sun and other lifestyle factors.
Investigators found that both lactose intake and consumption of whole milk were significantly associated with an increased risk of ovarian cancer risk in African-American women. No association was found for skim milk, low-fat milk, cheese and yogurt products.
Calcium intake, whether through food and/or supplement, linked to a decreased risk of the disease. There was also some evidence suggesting that women who spent 23 or more hours a week outside during the summer months had lower risk of ovarian cancer compared to women who spent six or fewer hours outside per week. There was no data on sunscreen or clothing and this link did not hold during the daylight hours for the entire year. And as the authors point out, the benefits of synthesizing vitamin D through sun exposure exposes individuals to increased risk of skin cancer.
“Because the benefits of increased sun exposure in African-American women may be offset by an increased risk of skin cancer, a combination of moderate sun exposure coupled with sufficient vitamin D intake from diet and supplements may be a safer solution for adequate vitamin D levels,” the authors write.
Like all case control studies, limitations include that having the disease may bias recall. Here, the women were asked to report their diet one year before diagnosis.
The study was supported by the New Jersey Commission on Cancer Research. The African American Cancer Epidemiology Study (AACES) study was funded by NCI and additional support was other state and federal funds.
Bo Qin et al. Dairy, calcium, vitamin D and ovarian cancer risk in African–American women. British Journal of Cancer (2016), 1–9.
Centers for Disease Control. Ovarian Cancer Rates by Race and Ethnicity.