Vitamin D and calcium intake in relation to risk of endometrial cancer: A systematic review of the literature

Objective In response to a recent ecologic study of UV exposure and endometrial cancer incidence, we present the epidemiologic evidence on the relation between intake of vitamin D and its metabolically related nutrient, calcium, and the occurrence of endometrial cancer. Methods We conducted a systematic literature review and meta-analysis of vitamin D and calcium in relation to endometrial cancer, including peer-reviewed manuscripts published up to May 2007. Random and fixed effects summary estimates were computed. Results Pooled analyses of the three case-control studies of dietary vitamin D and endometrial cancer uncovered heterogeneous results that were not significant in random or fixed effects analyses. Cut-points for the highest vitamin D intakes ranged from > 244 to > 476 IU/day. Qualitatively similar findings were observed for dietary calcium. Only two studies provided estimates for calcium supplements (random effects OR = 0.62, 95% CI 0.39–0.99; fixed effects OR = 0.62, 95% CI 0.42–0.93, for top vs. bottom category, p for heterogeneity = 0.25). Conclusions The limited epidemiological evidence suggests no relation between endometrial cancer in the ranges of dietary vitamin D examined, and suggests a possible inverse association for calcium from supplements. Prospective studies, ideally including plasma 25(OH) D to estimate vitamin D input from diet and sun exposure, are needed to further explore these hypotheses.