The results of the study, conducted at Sweden's Karolinska Institute, make it more difficult for women to discern the advantages and disadvantages of taking vitamin supplements.
The study followed 35,000 women over a 10-year period. Susanna Larrson, the lead author of the study, says, "Results from this prospective study suggest that the use of multivitamins may increase the risk of breast cancer."
The reasons for the connection between multivitamins and breast cancer are not entirely clear. However, the researchers hypothesize that regular consumption of multivitamin supplements may increase the density of breast tissue, which is a known risk factor for breast cancer. In addition, folic acid has been shown to stimulate tumor growth.
However, Australian experts have expressed concern about potential limitations of the study. The Complementary Healthcare Council of Australia believes that the study relied too much on self-reports and did not thoroughly consider the bioactivity of multivitamin components.
However, most agree that the study reinforces an important concept: taking pills is not a solution to meeting our nutritional needs. Kathy Chapman, of the Cancer Council Australia says, "It reinforces the importance of eating fresh fruit and vegetables rather than people thinking they can get more of their nutrition from a pill. What we've learned over time in cancer is that quick fixes aren't a good idea." In general, experts around the world recommend eating a healthy diet to get the vitamins and minerals we need, rather than taking supplements.