Doi:10.1093/aje/kwn198 Original Contribution Vitamin D From Dietary Intake and Sunlight Exposure and the Risk of Hormone-Receptor-Defined Breast Cancer

Evidence has emerged for a role of vitamin D in the development of breast cancer, and there is some suggestion that its antiproliferative effect is greater in hormone-receptor-positive cells. Few epidemiologic studies have con-sidered the association between vitamin D and hormone-receptor-defined breast cancer, and the results are conflicting. Considering 759 cases and 1,135 controls from a case-control study (Ontario, Canada, 2003–2005), the authors examined the association between vitamin D intake at specific ages and combined estrogen-receptor-(ER) and progesterone-receptor- (PR) defined breast cancer. While increased intake of vitamin D (from the sun and diet) was most consistently associated with a significantly reduced risk of ERþ/PRþ tumors (e.g., odds ratio 0.76, 95 % confidence interval: 0.59, 0.97 for use of cod liver oil during adolescence), comparable nonsignificant associations were found for receptor-negative (ER/PR) (odds ratio 0.74, 95 % confidence interval: 0.53, 1.04) and mixed (ERþ/PR) (odds ratio 0.79, 95 % confidence interval: 0.51, 1.22) tumors. This study suggests that vitamin D is associated with a reduced risk of breast cancer regardless of ER/PR status of the tumor. Future studies with a larger number of receptor-negative and mixed tumors are required. breast neoplasms; case-control studies; diet; receptors, estrogen; receptors, progesterone; sunlight; vitamin D Abbreviations: ER, estrogen receptor; PR, progesterone receptor; 1,25(OH)2D, 1,25-dihydroxyvitamin D (calcitriol); 25(OH)D, 25-hydroxyvitamin D (calcidiol)