The Significance of Vitamin D Status in Breast Cancer: A State of the Science Review

The potential role of vitamin D in the development of breast cancer has been the subject of considerable interest. Laboratory and genetic studies demonstrate promising anticarcinogenic effects of vitamin D. However, inconsistencies persist in results of human studies that have assessed vitamin D supplementation for the prevention of primary and secondary cancers. Despite these discrepancies, screening for vitamin D deficiency and vitamin D supplementation have increased dramatically in the past decade. No official institutional guidelines recommend vitamin D supplementation for cancer prevention, and yet these newly adopted practice norms have outpaced rigorous scientific study. Higher circulating levels of vitamin D [25-hydroxyvitamin D, or 25(OH)D] appear to be associated with reduced risk and improved survivorship of certain malignancies. However, the association has not been found for all cancers. This state of the science review examines the association between vitamin D supplementation, circulating 25(OH)D level, vitamin D receptor polymorphisms, and the risk and mortality of breast cancer. The review addresses the role of supplementation and optimal 25(OH)D levels.