Vitamin D, calcium, and mammographic breast densities. Cancer Epidemiol Biomarkers Prev 2004

Vitamin D and calcium are being evaluated as potential breast cancer prevention agents. This study reports on the relation of dietary vitamin D and calcium to mammographic breast densities, one of the strongest breast cancer risk factors. Participants were women ages 40 to 60 years who had had a screening mammogram in Rhode Island and eastern Massachusetts (1989–1990). Diet was assessed by semiquantitative food frequency questionnaire, and the percentage of the breast showing densities was estimated visually by a single observer without information on subjects. Multivariate logistic regression was used to compare dietary intakes of vitamin D and calcium between women classified as having few densities (V30 % of the breast with density, n = 287) and extensive densities (z70 % of the breast with density, n = 256). For categories of increasing vitamin D intake (<50, 50–99, 100–199, and z200 IU/d), adjusted odds ratios (OR) for extensive densities were 1.00 (reference), 0.51, 0.37, and 0.24, respectively (P for trend = 0.0005). For increasing calcium intake (<500, 500– 749, 750–999, and z1,000 mg/d), adjusted ORs were 1.00 (reference), 0.63, 0.25, and 0.24, respectively (P for trend = 0.0006). Combination of higher intakes of vitamin D and calcium (z100 IU/d and z750 mg/d, respectively) were associated with a reduction of breast densities (OR, 0.28; 95 % confidence interval, 0.15–0.54) compared with those consuming <100 IU/d and <750 mg/d. Increases in vitamin D and calcium intakes were as-sociated with decreases in breast densities, suggesting that dietary vitamin D and calcium could reduce breast cancer risk possibly through influences on breast tissu