Calcium, Vitamin D Intake May Lower Risk for Premenopausal Breast Cancer

May 31, 2007 — Women who have high intakes of calcium and vitamin D have a lower risk of developing premenopausal breast cancer, according to the results of a prospective study published in the May 28 issue of the Archives of Internal Medicine.

"Animal data suggest the potential anticarcinogenic effects of calcium and vitamin D on breast cancer development," write Jennifer Lin, PhD, from the Harvard Medical School in Boston, Massachusetts, and colleagues. "However, epidemiologic data relating calcium and vitamin D levels to breast cancer have been inconclusive."

The investigators prospectively evaluated total calcium and vitamin D intakes in relation to breast cancer incidence in a group of women enrolled in the Women's Health Study. Participants were 10,578 premenopausal and 20,909 postmenopausal women 45 years or older who were free of cancer and cardiovascular disease at baseline. A food frequency questionnaire was used to evaluate baseline dietary intake, and Cox proportional hazards regression was used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs).

During an average of 10 years of follow-up, incident invasive breast cancer was confirmed in 276 premenopausal and 743 postmenopausal women. Higher intakes of total calcium and vitamin D were moderately associated with a lower risk for premenopausal breast cancer. In the group with the highest compared with the lowest quintile of intake, HRs were 0.61 (95% CI, 0.40 - 0.92) for calcium (P = .04 for trend) and 0.65 (95% CI, 0.42 - 1.00) for vitamin D intake (P = .07 for trend).

The inverse association with intakes of calcium and vitamin D was also present for large or poorly differentiated breast tumors in premenopausal women (P ? .04 for trend). Among postmenopausal women, however, intakes of both nutrients were not inversely associated with the risk for breast cancer.

Study limitations include nutrient intakes only being assessed once at baseline and being subject to measurement error, lack of information about vitamin D intake from sunlight exposure, and findings being subject to chance because of multiple subgroup analyses.

"Findings from the present study suggest that higher intakes of calcium and vitamin D from dietary plus supplemental sources may be associated with a lower risk of breast cancer among premenopausal women," the authors conclude. "The inverse association in premenopausal women may be more pronounced in more aggressive breast tumors. Further investigation is warranted to study the potential utility of calcium and vitamin D intake in reducing the risk of breast cancer."

The National Cancer Institute and the National Heart, Lung, and Blood Institute supported this study. The authors have disclosed various financial relationships with the National Institutes of Health (National Heart, Lung, and Blood Institute and National Cancer Institute), Roche Molecular Systems, and/or Bayer.

Arch Intern Med. 2007;167:1050-1059.

Source: http://www.medscape.com/viewarticle/557532?src=mp