A recent study that involved thousands of postmenopausal women has produced results that suggest women with invasive breast cancer could benefit from taking supplements that contain both multivitamins and minerals. This new research found that the risk of dying from invasive breast cancer was 30 percent lower among participants that took a multivitamin and mineral combination compared to those that did not.

“Our study offers tentative but intriguing evidence that multivitamin/mineral supplements may help older women who develop invasive breast cancer survive their disease,” said Sylvia Wassertheil-Smoller, Ph.D., lead author of the study and distinguished university professor emerita of epidemiology and population health at Albert Einstein College of Medicine of Yeshiva University.

Multivitamin and mineral combination supplements are the most commonly consumed type of dietary supplement among U.S. adults. They typically contain 20 to 30 vitamins and minerals at levels of 100 percent of the U.S. Recommended Dietary Allowances or less. Most often the labeling suggests taking these supplements on a daily basis.

This research was conducted as part of the Women’s Health Initiative Clinical Trials and the Women’s Health Initiative (WHI) Observational Study. The two studies include data from 161,608 postmenopausal women between the ages of 50 and 79 when they first joined the study. These women were enrolled  between the years 1993 and 1998 at 40 different locations across the United States.

After enrollment and during repeated follow-up visits, all participants provided extensive information about their health. This included whether or not they had taken a multivitamin and mineral combination supplement at least once a week during the last two weeks.

Around 38 percent of the 7,728 women who developed invasive breast cancer during the study reported using the supplements. Most were taking the supplements before their breast cancer diagnosis.

Researchers looked at several possible confounding factors including additional supplements that the women took, their smoking status, education, race and ethnicity, weight, depression, alcohol use, physical activity, age at breast cancer diagnosis, and diabetes. The association between regular use of multivitamin and mineral combination supplements and reduced risk of death persisted even after these factors were considered.

“Controlling for these other factors strengthens our confidence that the association we observed – between taking multivitamin/mineral supplements and lowering breast-cancer mortality risk among postmenopausal women with invasive breast cancer – is a real one,” said Dr. Wassertheil-Smoller, who also holds the Dorothy and William Manealoff Foundation and Molly Rosen Chair in Social Medicine Emerita. “But further studies are needed to confirm whether there truly is a cause-and-effect relationship here. And our findings certainly cannot be generalized to premenopausal women diagnosed with invasive cancer or to other populations of women.”

This study was published in Breast Cancer Research and Treatment.