Date of Defense:
August 19, 2009
Objectives: Recent studies suggest that vitamin D deficiency is associated with increased risk of some cancers. No large cohort study has examined dietary vitamin D and endometrial cancer risk.
Methods: Using data from a large prospective cohort study, the association between dietary and supplemental intake of vitamin D and incident endometrial cancer was examined. A total of 23,348 women who completed a questionnaire were followed for endometrial cancer incidence from 1986-2004. Age-adjusted and multivariate-adjusted hazard ratios (HR) and their 95% confidence intervals (CI) were calculated using proportional hazards regression.
Results: The association between dietary vitamin D intake and endometrial cancer was borderline significant. Women who consumed >800 IU/day total vitamin D were at elevated risk for endometrial cancer than women consuming <400 IU/day (HR: 1.31, 95% CI: 0.99-1.75). Excluding diet, women who consumed <400 IU/day supplemental vitamin D were at significant higher risk for developing endometrial cancer than women who did not take supplements (HR: 1.40, 95% CI: 1.08-1.82). However, there was no association among women taking vitamin D supplements with >400 IU/day and risk of developing endometrial cancer (HR: 1.06, 95% CI: 0.85-1.32).
Conclusions: Prospective studies evaluating supplemental and dietary intake of vitamin D that include sunlight exposure of vitamin D are needed to better understand the relationship between vitamin D exposure and risk for endometrial cancer.