Master's Project Title:

Vitamin D Intake and Endometrial Cancer Risk in Postmenopausal Women: The Iowa Women’s Health Study

MCH Student:

Sarah Klawitter

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.