Breast cancer patients with higher vitamin D levels at the time they’re diagnosed showed significantly better outcomes in the long-term, according to a new research study from Kaiser Permanente and Roswell Park Cancer Institute.
The study, “Association of Serum Level of Vitamin D at Diagnosis With Breast Cancer Survival,” was published in JAMA Oncology.
Vitamin D is a nutrient famous for its role in preserving healthy bones. The most well-known sources of vitamin D include sunlight, fatty fish oils, and nutritional supplements, in addition to fortified milk and cereals.
While the full connection between vitamin D and breast cancer outcomes is not fully understood, a deficiency of vitamin D was thought to influence the outcomes of breast cancer survivors in the long run.
Long associated with the risk for several cancers, vitamin D is believed to be involved in promoting the normal development of mammary cells, as well as in inhibiting the proliferation of cancer cells.
“We found that women with the highest levels of vitamin D had about a 30 percent better likelihood of survival than women with the lowest levels of vitamin D,” Lawrence H. Kushi, ScD, lead researcher of the Pathways study of breast cancer survivors, said in a press release.
Funded by the National Cancer Institute, the Pathways study was a prospective cohort study of breast cancer survivors established in 2006. The study enrolled 1,666 participants who provided blood samples within two months of their breast cancer diagnosis, and who were followed at 12, 24, 48, 72 and 96 months after their baseline interview. They were asked questions about diet, lifestyle, and other risk factors.
“With the extremely rich data sources from a large sample size, we were able to prospectively analyze three major breast cancer outcomes— recurrence, second primary cancer and death,” said Song Yao, PhD, the study’s lead author and associate professor of oncology at Roswell Park.
“We were also able to adjust for multiple possible contributing factors that could influence vitamin D levels such as age, obesity, race and ethnicity, socioeconomic status, and several tumor characteristics that are known to influence breast cancer outcomes — to ensure that the effects we observed were independent of these factors.”
Besides being associated with overall lower mortality rates, vitamin D was also found to have an even stronger effect in premenopausal women (63 percent improvement); in women with recurrence-free breast cancer (48 percent improvement); and in women with invasive-disease-free survival (42 percent improvement) during a median follow-up of 84 months.
The difference between taking this nutrient from natural sources or from supplements was not specifically addressed in this study, but Kushi noted that it reinforces the previously established recommended daily levels – 600 IU (international units) for people up to age 70 and pregnant or breastfeeding women, and 800 IU for people older than age 7o.
“The more we know about vitamin D, the more we understand that it may play a key role in cancer prevention and prognosis,” Kushi added. “This study adds to the evidence that vitamin D is an important nutrient.”