WHAT IS VITAMIN D? Vitamin D is a fat soluble vitamin. Although many people associate vitamin d with healthy bones, they are unaware of the many other essential functions of vitamin d in our bodies. In addition to facilitating calcium absorption, vitamin d is needed for healthy immunity, cardiovascular function and hormones. HOW DO WE BECOME DEFICIENT? Most of the vitamin d is produced by our body, as a result of regular sun exposure. Although in countries like Australia wher