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Cancer Epidemiol Biomarkers Prev. 2012 Mar;21(3):462-73. doi: 10.1158/1055-9965.EPI-11-1009. Epub 2012 Jan 17.

Vitamin D and calcium supplementation and one-year change in mammographic density in the women's health initiative calcium and vitamin D trial.

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  • 1Division ofBiostatistics and Epidemiology,University of Massachusetts, Amherst, Massachusetts 01003, USA.



Calcium and vitamin D may be inversely related to breast cancer risk, in part by affecting mammographic density. However, results from previous, mostly cross-sectional studies have been mixed, and there have been few randomized clinical trials of the effect of calcium and vitamin D supplementation on change in mammographic density.


We assessed the effect of one year of supplementation on mammographic density in 330 postmenopausal women enrolled in the Women's Health Initiative hormone therapy (HT) and calcium and vitamin D (CaD) trials. Women were randomized to receive 1,000 mg/d of elemental calcium carbonate plus 400 IU/d of vitamin D(3) or placebo.


After approximately one year, mammographic density decreased 2% in the CaD supplementation group and increased 1% in the placebo group (ratio of means = 0.97; 95% CI = 0.81-1.17). Results suggested potential interaction by HT use (P = 0.08). Among women randomized to HT placebo, the ratio of mean density comparing CaD supplementation and placebo groups was 0.82 (95% CI = 0.61-1.11) vs. 1.16 (95% CI = 0.92-1.45) in women randomized to active HT. In sensitivity analyses limited to women taking ≥ 80% of study supplements, ratios were 0.67 (95% CI = 0.41-1.07) in women not assigned to HT and 1.07 (95% CI = 0.79-1.47) women assigned to HT.


We observed no overall effect of vitamin D and calcium supplementation on mammographic density after one year.


Potential interaction between these nutrients and estrogen as related to mammographic density warrants further study.

©2012 AACR.

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