Vitamin D and calcium intakes and breast cancer risk in pre- and postmenopausal women123

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Background: Some evidence suggests that vitamin D may reduce breast cancer risk. Despite the biological interaction between vitamin D and calcium, few studies have evaluated their joint effects on breast cancer risk.Objective: The objective was to evaluate the associations and potential interaction between vitamin D and calcium (from food and supplements) and breast cancer risk in a population-based case-control study.Design: Breast cancer cases aged 25–74 y (diagnosed 2002–2003) were identified through the Ontario Cancer Registry. Controls were identified by using random digit dialing; 3101 cases and 3471 controls completed epidemiologic and food-frequency questionnaires. Adjusted odds ratios (ORs) and 95% CIs were estimated by using multivariate logistic regression.Results: Vitamin D and calcium intakes from food only and total combined intakes (food and supplements) were not associated with breast cancer risk, although the mean intake of vitamin D was low. Vitamin D supplement intake >10 μg/d (400 IU/d) compared with no intake was associated with a reduced risk of breast cancer (adjusted OR: 0.76; 95% CI: 0.59, 0.98). No categories of calcium supplement intake were significantly associated with reduced breast cancer risk, but a significant inverse trend was observed (P = 0.04). There were no significant interactions involving vitamin D, calcium, or menopausal status.Conclusions: No associations were found between overall vitamin D or calcium intake and breast cancer risk. Vitamin D from supplements was independently associated with reduced breast cancer risk. Further research is needed to investigate the effects of higher doses of vitamin D and calcium supplements.

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From Population StudiesSurveillance Cancer Care Ontario Toronto Canada (LNAMC); the Dalla Lana School of Public Health University of Toronto Toronto Canada (LNA MCJAK); the Department of PathologyLaboratory Medicine Mount Sinai Hospital Toronto Canada (RV);the Prosserman Centre for Health Research Samuel Lunenfeld Research Institute Mount Sinai Hospital Toronto Canada (JAK).

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The Ontario Women’s Diet and Health Study was supported by the Canadian Breast Cancer Research Alliance with special support by the Canadian Breast Cancer Foundation Ontario Chapter (grant no. 13572). LNA was supported by a Canadian Institutes of Health Research Doctoral Research Award in Public Health.

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Address correspondence to LN Anderson, Population Studies and Surveillance, Cancer Care Ontario, 620 University Avenue, Toronto, ON M5G 2L7, Canada. E-mail:[email protected].