STOCKHOLM, Sweden—Many women use multivitamins assuming these supplements will prevent chronic diseases such as cancer and cardiovascular disease (CVD); however, results from a published study in the American Journal of Clinical Nutrition suggest multivitamin use is associated with an increased risk of breast cancer (2010; DOI: 10.3945/ajcn.2009.28837). However, the researchers did note the observation merits further investigation.
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. During a mean follow-up of 9.5 years, 974 women were diagnosed with incident breast cancer. Multivitamin use was associated with a statistically significant increased risk of breast cancer. The multivariable relative risk of women who reported the use of multivitamins was 1.19. The association did not differ significantly by hormone receptor status of the breast tumor.
Andrew Shao, senior vice president, scientific and regulatory affairs, Council of Responsible Nutrition (CRN), commented on the study’s findings, stating: “As observational studies go, this one appears to have been well-done overall. It was a large, prospective cohort of more than 35,000 women who were healthy at baseline and followed for almost 10 years. The finding of an increased risk of breast cancer is puzzling, and in direct conflict with other similarly designed studies such as the well-regarded Nurses Health Study out of Harvard, which showed just the opposite—that multivitamin use was associated with a significant decrease in breast cancer risk. And there are a few other studies that show ‘no effect.’ So it is difficult to say what this study means on its own. To their credit, the authors are balanced in their discussion of the findings and are careful not to draw firm conclusions from this one study. More research is definitely needed to sort out the conflicting data. In the meantime, the message to consumers is still the same: it is better to meet your nutrient needs than not, and a simple, affordable daily multivitamin helps us all to achieve that. This study does not change that.”
