Many breast cancer patients are deficient in vitamin D, according to the results of a study presented at the American Society of Clinical Oncology breast cancer symposium on October 8, 2009 in San Francisco.
Vitamin D is a fat-soluble vitamin that comes from dietary supplements, exposure to sunlight, and foods such as fortified milk and cereal and certain kinds of fish (including salmon, mackerel, and tuna). Low levels of circulating vitamin D have been linked to worse outcomes for breast cancer patients. In addition, vitamin D deficiency can result in reduced bone mineral density, thereby increasing the risk of bone fractures. The association between levels of vitamin D and risk for certain types of cancer continues to be evaluated.
Researchers from New York analyzed vitamin D levels in 166 women with non-metastatic breast cancer who were undergoing one or more of the following treatments: hormone therapy, radiation, and chemotherapy. They found that 69% of the women had vitamin D deficiency. Non-whites and women with late-stage breast cancer had the lowest levels of vitamin D.
The researchers found that weekly high-dose vitamin D supplementation (50,000 IU or more) increased vitamin D levels more than conventional low-dose supplementation. (It is important to note that high doses of vitamin D are safe for short-term use in order to correct a deficiency; however, could potentially be dangerous for the long-term.)
Low vitamin D levels puts women with breast cancer at a greater risk of fractures. It is unclear whether vitamin D plays a role in the incidence or outcomes of breast cancer. Future research will continue to evaluate this link.
 Peppone LJ, et al. Vitamin D deficiency prevalent in women being treated for breast cancer; High-dose supplementation can increase vitamin D blood levels. American Society of Clinical Oncology Breast Cancer Symposium, Abstract 211. Presented October 8, 2009.
 Goodwin P, Ennis M, Pritchard K, Koo J, Hood N. Vitamin D is common at breast cancer diagnosis and is associated with a significantly higher risk of distant recurrence and death in a prospective cohort study of T1-3, N0-1, M0 BC. Early Release Proceedings from the 2008 American Society of Clinical Oncology. Abstract #511.