Calcium plus vitamin D supplementation and the risk of breast cancer.

Academic Article


  • BACKGROUND: Although some observational studies have associated higher calcium intake and especially higher vitamin D intake and 25-hydroxyvitamin D levels with lower breast cancer risk, no randomized trial has evaluated these relationships. METHODS: Postmenopausal women (N = 36 282) who were enrolled in a Women's Health Initiative clinical trial were randomly assigned to 1000 mg of elemental calcium with 400 IU of vitamin D(3) daily or placebo for a mean of 7.0 years to determine the effects of supplement use on incidence of hip fracture. Mammograms and breast exams were serially conducted. Invasive breast cancer was a secondary outcome. Baseline serum 25-hydroxyvitamin D levels were assessed in a nested case-control study of 1067 case patients and 1067 control subjects. A Cox proportional hazards model was used to estimate the risk of breast cancer associated with random assignment to calcium with vitamin D(3). Associations between 25-hydroxyvitamin D serum levels and total vitamin D intake, body mass index (BMI), recreational physical activity, and breast cancer risks were evaluated using logistic regression models. Statistical tests were two-sided. RESULTS: Invasive breast cancer incidence was similar in the two groups (528 supplement vs 546 placebo; hazard ratio = 0.96; 95% confidence interval = 0.85 to 1.09). In the nested case-control study, no effect of supplement group assignment on breast cancer risk was seen. Baseline 25-hydroxyvitamin D levels were modestly correlated with total vitamin D intake (diet and supplements) (r = 0.19, P < .001) and were higher among women with lower BMI and higher recreational physical activity (both P < .001). Baseline 25-hydroxyvitamin D levels were not associated with breast cancer risk in analyses that were adjusted for BMI and physical activity (P(trend) = .20). CONCLUSIONS: Calcium and vitamin D supplementation did not reduce invasive breast cancer incidence in postmenopausal women. In addition, 25-hydroxyvitamin D levels were not associated with subsequent breast cancer risk. These findings do not support a relationship between total vitamin D intake and 25-hydroxyvitamin D levels with breast cancer risk.
  • Keywords

  • Aged, Body Mass Index, Breast Neoplasms, Calcium Compounds, Carcinoma, Ductal, Breast, Case-Control Studies, Dietary Supplements, Double-Blind Method, Drug Administration Schedule, Female, Humans, Incidence, Kaplan-Meier Estimate, Mammography, Middle Aged, Odds Ratio, Patient Selection, Postmenopause, Proportional Hazards Models, Risk Assessment, Risk Factors, United States, Vitamin D
  • Digital Object Identifier (doi)

    Author List

  • Chlebowski RT; Johnson KC; Kooperberg C; Pettinger M; Wactawski-Wende J; Rohan T; Rossouw J; Lane D; O'Sullivan MJ; Yasmeen S
  • Start Page

  • 1581
  • End Page

  • 1591
  • Volume

  • 100
  • Issue

  • 22