Abstract
Background: Ovarian cancer is the leading cause of death from gynecologic cancers in the US. Currently there is no reliable screening available for ovarian cancer. Most cases are diagnosed at an advanced stage, with a poor survival rate. Therefore, a better understanding of the etiology and prevention is especially important for ovarian cancer. It has been hypothesized lactose in dairy may have a direct toxicity effect on oocytes, while the other two abundant nutrients from dairy foods, calcium and vitamin D, may have anti-tumorigenic properties. In addition to food and supplemental intakes, vitamin D in humans can also be achieved through skin synthesis upon sun exposure. However, darker skin color may reduce the penetration of ultraviolet-B, resulting in the lower cutaneous synthesis of vitamin D. This, together with the tendency of African Americans (AAs) to have lower consumption of vitamin D and calcium from dietary and supplemental sources, place AA women at risk for vitamin D and calcium deficiency.
Objective: To evaluate intakes of dairy foods, lactose, calcium, and vitamin D exposure (through diet, supplement and sunlight) and the risk of ovarian cancer among AA women.
Methods: We evaluated these associations among 490 ovarian cancer cases and 656 controls of AA descent recruited from the African American Cancer Epidemiology Study, a population-based case-control study in 11 geographical areas in the US. Cases were identified through rapid case ascertainment and age- and site-frequency matched controls were identified by random-digit-dialing. Information on risk factors related to ovarian cancer was collected by a computer-assisted telephone interview. Daily hours spent outdoors in daylight were asked separately on weekdays or weekends, and in summer or the rest of the year. Dietary information was assessed via a self-administered Block 2005 food frequency questionnaire (FFQ). Supplemental intake of calcium or vitamin D including multivitamin sources was also collected. Multivariable logistic regression models were used to estimate odds ratios (OR) and 95% confidence intervals (CI) adjusted for relevant sociodemographic, reproductive, and lifestyle risk factors.
Results: In the multivariable- and mutually-adjusted model, whole milk consumption was significantly associated with increased ovarian cancer risk (OR=1.85 comparing consumers with above-median intake vs. non-consumers, 95% CI: 1.05-3.27; p-trend: 0.023). No association was observed for skim/low-fat milk, cheese or yogurt. Lactose intake was found to increase ovarian cancer risk [OR=1.97 comparing the highest quartile (Q4) vs. lowest (Q1), 95% CI: 1.25-3.10; p-trend: 0.008]. Calcium intake was consistently associated with a decreased risk, with a similar OR for calcium from food, supplement, or total from both sources when comparing the highest to the lowest intake category. For example, total calcium intake was associated with a 49% decreased OR comparing Q4 vs. Q1 (95% CI: 0.30-0.86; p-trend: 0.009). Although we found no association with total and dietary vitamin D intakes, more daylight hours spent outdoors in summer months predicted a lower risk of ovarian cancer (OR=0.71 comparing Q4 vs. Q1, 95% CI: 0.51-0.99; p-trend: 0.049).
Conclusion: Our findings suggest, for the first time, that sun exposure in summer months and a high-calcium, low-lactose diet may decrease the risk of ovarian cancer in AA women. Considering that there is no effective screening tool for ovarian cancer and the poorer survival of AA patients, if replicated in future studies these results open up potential preventive strategies through lifestyle or dietary modifications.
Citation Format: Bo Qin, Patricia G. Moorman, Anthony J. Alberg, Jill S. Barnholtz-Sloan, Melissa Bondy, Michele L. Cote, Ellen Funkhouser, Edward S. Peters, Ann G. Schwartz, Paul Terry, Joellen M. Schildkraut, Elisa V. Bandera. Dairy, calcium, vitamin D and ovarian cancer risk in African-American women. [abstract]. In: Proceedings of the Ninth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2016 Sep 25-28; Fort Lauderdale, FL. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2017;26(2 Suppl):Abstract nr B51.
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