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This Article Full Text (Publish Ahead of Print[PDF]) All Versions of this Article: 89/1/277    most recent ajcn.2008.26704v1 Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Larsson, S. C Articles by Wolk, A. Search for Related Content PubMed PubMed Citation Articles by Larsson, S. C Articles by Wolk, A. Agricola Articles by Larsson, S. C Articles by Wolk, A.

Long-term dietary calcium intake and breast cancer risk in a prospective cohort of women^1,2,3

¹ From the Division of Nutritional Epidemiology, National Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden (SCL and AW), and the Department of Surgery and Centre for Clinical Research, Central Hospital, Västerås, Sweden (LB).

² Supported by research grants from the Swedish Cancer Foundation and the Swedish Research Council for Infrastructure.

³ Reprints not available. Address correspondence to SC Larsson, Division of Nutritional Epidemiology, National Institute of Environmental Medicine, Karolinska Institutet, Box 210, SE-17177 Stockholm, Sweden. E-mail: susanna.larsson{at}ki.se.

ABSTRACT

Background: Calcium may potentially influence the risk of breast cancer because of its role in regulating cell proliferation, differentiation, and apoptosis. However, prospective studies of calcium intake in relation to breast cancer incidence are sparse.

Objective: The objective of this study was to prospectively examine and show the association, if any, of dietary calcium intake with risk of breast cancer by estrogen receptor (ER) and progesterone receptor (PR) status of the tumor.

Design: The Swedish Mammography Cohort is a population-based prospective cohort of 61,433 women who were cancer-free at enrollment in 1987–1990. Dietary calcium intake was assessed with a food-frequency questionnaire at baseline and again in 1997. Cox proportional hazards models were used to estimate rate ratios (RRs) and 95% CIs, adjusted for breast cancer risk factors.

Results: During an average of 17.4 y of follow-up, 2952 incident cases of invasive breast cancer were ascertained. Dietary calcium intake was not associated with risk of overall breast cancer; the multivariate RR for the highest compared with the lowest quintile of calcium intake was 0.97 (95% CI: 0.87, 1.09; P for trend: 0.49). There was a statistically significant inverse trend for ER-negative/PR-negative (ER–/PR–) breast cancer (P for trend: 0.02); the multivariate RR for the comparison of extreme quintiles of calcium intake was 0.66 (95% CI: 0.44, 0.99). Calcium intake was not associated with ER-positive/PR-positive (ER+/PR+) or ER+/PR– tumors.

Conclusions: Our findings do not support an association between dietary calcium intake and overall breast cancer risk. The inverse relation between calcium intake and ER–/PR– breast cancer requires confirmation in other studies.

Received for publication July 16, 2008. Accepted for publication September 25, 2008.

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