The Association between Dietary Calcium Intake and Breast Cancer Risk among Iranian Women

Abstract

Background: No information is available from Middle Eastern countries linking dietary calcium intake and odds of breast cancer. Objective This study was conducted to investigate the association between dietary calcium intake and odds of having breast cancer among Iranian women. Methods: In this population-based case-control study, 350 newly diagnosed breast cancer cases were recruited and 700 age-matched subjects were enrolled as controls. Dietary intakes were examined by the use of a 106-item validated FFQ. Total dietary calcium intake of each participant was computed by summing up calcium intake from all foods and dishes. The quartile cutoff points of energy-adjusted calcium intake was obtained in the control group. These cutoff points were used to classify all study participants into quartiles in terms of dietary calcium intake. Results: After adjustment for age and energy intake, we found that individuals in second quartile of calcium intake were 43% less likely to have breast cancer compared with those in the bottom quartile (OR: 0.57; 95% CI: 0.38–0.86). This significant association disappeared after further controlling for other potential confounders including dietary factors and BMI (OR: 0.91; 95% CI: 0.57–1.45). When the analyses were done by menopausal status, premenopausal women with the greatest calcium intake were 60% less likely to have breast malignancy than those with the lowest intake (OR: 0.40; 95% CI: 0.16–0.99). Adjustment for potential confounders did not substantially influence this finding (OR: 0.32; 95% CI: 0.11–0.95). The association remained significant even after additional controlling for dietary covariates (OR: 021; 95% CI: 0.06–0.72) and BMI (OR: 0.21; 95% CI: 0.04–0.93). No significant association was found between dietary calcium intakes and odds of breast cancer in postmenopausal women. Discussion: Dietary calcium intake was protectively associated with odds of breast cancer in premenopausal women, but not in postmenopausal women. Further prospective investigations are needed to confirm these findings.