Researchers find that multivitamin use among breast cancer patients may help save their lives.

People suffering from invasive breast cancer may have another tool to add to their arsenal for fighting the disease, according to a newly released study.

Researchers found evidence that postmenopausal patients who take multivitamins with minerals on a regular basis have a 30 percent lower rate of death when compared with those who don’t take the supplement. The research was conducted in collaboration with the Women’s Health Initiative Clinical Trials and the Women’s Health Initiative Observational Study.

The effect of multivitamins and mineral supplements on breast cancer patients has been somewhat controversial in recent years, as multiple studies have shown mixed results. This study, however, was among those with the largest number of participants, making its results more reliable, said Sylvia Wassertheil-Smoller, lead author of the study and professor emerita of epidemiology and population health at the Albert Einstein College of Medicine of Yeshiva University.

“It’s clear we need a lot more studying on this,” Wassertheil-Smoller said. “There are a lot of unknowns about this, and there should be a lot more research on it in the mainstream.”

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The Women’s Health Initiative enrolled 161,608 postmenopausal women, ages 50 to 79, at 40 clinical centers in the United States from 1993 to 1998. The most current study focused on just over 7,700 participants who were diagnosed with invasive breast cancer during the earlier initial study, meaning that the cancer had spread into the breast tissue. They were then followed for an average of seven years.

Roughly 38 percent of the women who developed invasive breast cancer during the initial study used multivitamins and mineral supplements, which contain 20 to 30 vitamins and minerals. A majority took them prior to being diagnosed with breast cancer, according to the research.

Researchers involved in the study took into account other factors, including race/ethnicity, weight, depression, alcohol use, physical activity, age at breast cancer diagnosis, and diabetes. The reduced risk of death remained even when those factors were taken into account, the study authors wrote.

“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,” Wassertheil-Smoller said.

But officials at the American Cancer Society said more research needs to be done on the subject.

“These findings are interesting but need replication,” said Marji McCullough, strategic director for nutritional epidemiology at the American Cancer Society. “For breast cancer survivors, achieving and maintaining a healthy weight through a well-balanced diet and regular exercise is an important goal.”

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Wassertheil-Smoller said it’s too early for the research to affect how older patients with invasive breast cancer are treated. Instead, further studies need to be done.

“We don’t know the full affect,” she said. “We only had 321 that started taking the vitamins after the diagnosis. So, we don’t have the data basis to change the treatment [recommendations].”