Multivitamin use and breast cancer incidence in a prospective cohort of Swedish women

Multivitamin use and breast cancer incidence in a prospective cohort of  Swedish women

Susanna C Larsson, Agneta A kesson, Leif Bergkvist, and Alicja Wolk

ABSTRACT

Background: Many women use multivitamins in the belief that these supplements will prevent chronic diseases such as cancer and cardiovascular disease. However, whether the use of multivitamins affects the risk of breast cancer is unclear.

Objective: We prospectively examined the association between multivitamin use and the incidence of invasive breast cancer in

The Swedish Mammography Cohort.

Design: In 1997, 35,329 cancer-free women completed a self administered questionnaire that solicited information on multivitamin use as well as other breast cancer risk factors. Relative risks (RRs) and 95% CIs were calculated by using Cox proportional hazard models and adjusted for breast cancer risk factors.

Results: During a mean follow-up of 9.5 y, 974 women were diagnosed with incident breast cancer. Multivitamin use was associated with a statistically significant increased risk of breast cancer. The multivariable RR of women who reported the use of multivitamins was 1.19 (95% CI: 1.04, 1.37). The association did not differ significantly by hormone receptor status of the breast tumor.

Conclusions: These results suggest that multivitamin use is associated with an increased risk of breast cancer. This observed association is of concern and merits further investigation.

 Am J Clin Nutr 2010; 91:1268–72.

INTRODUCTION

There is a widespread use of multivitamin supplements in North America and Europe. Many people believe that these supplements will reduce the risk of chronic diseases such as cancer and cardiovascular disease. About 40% of US women Reported using multivitamins in 1999–2000 (1). Thus, the potential health benefits or adverse effects associated with multivitamin use are of great public health importance. Of concern, a recent study (2) showed that the use of multivitamin-multi mineral supplements was associated with higher breast density, which is directly related to breast cancer risk.

Epidemiologic studies (3–8) of the association between multivitamin use and breast cancer risk yielded inconsistent results. In the Nurses’ Health Study, the use of multivitamins was associated with a lower risk of breast cancer among women with high-alcohol consumption (6). In contrast, 2 other US cohort studies showed an increased risk of breast cancer associated with multivitamin use in the whole cohort (4) and in premenopausal women (5). Other US cohort studies (3, 7, 8) showed no association between multivitamin use and breast cancer risk.

We used data from a population-based cohort study of Swedish women to investigate the relation between multivitamin use and the risk of breast cancer overall and by the estrogen receptor (ER) and progesterone receptor (PR) status of the breast tumors.

SUBJECTS AND METHODS

Study cohort

Data used in the current study were obtained from participants of the Swedish Mammography Cohort. Details of this population based cohort study were reported previously (9). In brief, the cohort was established between 1987 and 1990 when all women born between 1914 and 1948 and living in central Sweden (Va¨stmanland and Uppsala countries) received a mailed questionnaire on diet and other risk factors for breast cancer. In the late autumn of 1997, all participants who were still alive and residing in the study area received a new questionnaire that was expanded to include ’350 items concerning diet and other lifestyle factors as well as dietary supplement use; 39,227 women (70%) completed the second questionnaire. For the current analyses, we used data from the 1997 questionnaire because information on supplement use was not obtained at baseline. We excluded women with an erroneous or a missing National Registration Number, women who did not provide information on supplement use, and women with a history of cancer other than non melanoma skin cancer, leaving 35,329 women aged 49–83 y for analysis. The study was approved by the Ethical Review Board at the Uppsala University Hospital (Uppsala, Sweden) and Karolinska Institutet (Stockholm, Sweden).
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