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


METHODS
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 microg/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.
Anderson
Laura N
LN
Cancer Care Ontario, Toronto, Canada. laura.anderson@cancercare.on.ca <laura.anderson@cancercare.on.ca>
Cotterchio
Michelle
M
Vieth
Reinhold
R
Knight
Julia A
JA
D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000453:epidemiology*; D002136:Calcium, Dietary / Q000008:administration & dosage*; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008875:Middle Aged; D015999:Multivariate Analysis; D009864:Ontario / Q000453:epidemiology; D017698:Postmenopause; D017697:Premenopause; D012044:Regression Analysis; D011795:Surveys and Questionnaires; D014807:Vitamin D / Q000008:administration & dosage*
D002136:Calcium, Dietary; D014807:Vitamin D