Multivitamins may cut breast cancer risk

Multivitamins and calcium supplements may help protect women against breast cancer, new research suggests.

The study involved 268 Puerto Rican women with breast cancer and 457 women without breast cancer, all of whom had been taking multivitamin tablets in the past five years (1). The women filled out detailed questionnaires asking which supplements they took, how frequently they took them, and whether they still took them. The women also gave blood samples so the researchers could measure the ability of their DNA to repair damage -a complex biological process that is critical to preventing cancer. A non-repaired DNA can lead to mutations and ultimately can cause cancer.

The results showed that taking multivitamin supplements was associated with a31% lowerlikelihood of having breast cancer. The use of calcium supplements was linked to a 40% reduced risk. The protective effect of vitamin combinations was also given when the body's own DNA repair mechanisms worked well. Calcium on the other hand, showed a cancer risk reducing effect especially when the DNA repair function was not optimal. This indicates that the additional vitamins may have a DNA repair independent anti-cancer effect.

Taking supplements of vitamins A, E, or C alone was associated with a slightly lower risk of breast cancer, but the finding could have been due to chance. This suggests that vitamins may workmore effectivelytogether than individuallyin lowering cancer risk.

In addition, the study showed that older age, reduced DNA repair capacity, a family history of breast cancer, and not breastfeeding all raised the risk of breast cancer.

Other studies have had conflicting results. Some have suggested that supplement forms of single vitamins such as A and E do not protect against breast cancer. Others have suggested that vitamins are protective. The researchers commented that dose and timing may explain the disparity: It could be that taking high doses later in life gives very different effects than taking the recommended amount of vitamins earlier on.

1. Matta J. et al. Presentation at the American Association for Cancer Research Annual Meeting, Washington, D.C. April 18, 2010.