Larsson, SC, A. Akesson, L. Bergkvist and A. Wolk. Multivitamin use and Breast Cancer Incidence in a Prospective Cohort of Swedish Women. Am J Clin Nutr. 2010 01 May; 915: 1268-1272. 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. IN THIS ISSUE: To paraphrase Shakespeare, "To [eat] or not to [eat]…that is the question," can also be said to apply to supplements like fiber and multivitamins when talking about cancer prevention. It seems that not only is the food you eat important for cancer prevention, but the supplements that you take are important as well. For instance, Larsson and colleagues found that women who take multivitamins have an increased risk of breast cancer. Having said that, Chan and Giovannucci found that taking calcium supplements was at least modestly beneficial against colorectal cancer, and Dahm et al. found that dietary fiber can reduce the risk of colorectal cancer. Bidoli and colleagues found that lignin (fiber) can reduce the risk of endometrial cancer and—in our study of the month—Hwang and others found that women with HPV who took multivitamins had a reduced risk of developing cervical cancer. IN side CANCERS Breast Cancer 1, 7-10 Colorectal Cancer 2-3 Hepatocellular Carcinoma 3 Endometrial Cancer 4 Malignant Lymphoma 5 Prostate Cancer 5 Thyroid Cancer 6 Nurses and Cancer 13 THERAPIES Nutrition 2, 11 Vitamin D 4, 12 Psychological Adjustment 12 STUDY OF THE MONTH 6 FOR THE LATEST IN WORLDWIDE INTEGRATED CANCER CARE RE UPDATES search RESEARCH UPDATES — 1 JULY 2010 BREAST CANCER To support this valuable educational service, please donate at: www.inspirehealth.ca/donate Research Updates is published once a month to provide the latest integrated cancer care research to patients, health care providers, and the public. www.inspirehealth.ca