In recent times, there has been a great deal of interest in vitamin D, with over 1000 publications in PubMed in 2011 alone. A remarkable number of studies dealing with novel aspects of its biological activity and its potential to exert broad-ranging effects beyond calcium and mineral homeostasis have emerged (1– 4). Vitamin D deficiency is a highly prevalent condition in the developed world and in the populous regions of Asia, India, and the Middle East. Significant downward trends in vitamin D status in U.S. population-based studies suggest that vitamin D deficiency/insufficiency is increasing in frequency. Accordingly, health agencies including the International Osteoporosis Foundation, The Endocrine Society, and Institute of Medicine have recently outlined recommendations for the prevention of vitamin D deficiency and have called for further research to guide the field.