For more than a century, scientists have recognised that Vitamin D3 is involved in bone health. The latest research, however, shows that Vitamin D3 deficiency is linked to a range of other health conditions such as depression, back pain, cancer, both insulin resistance and pre-eclampsia during pregnancy, impaired immunity and macular degeneration. While it is clear that a large percentage of individuals are deficient, what is also becoming apparent is that our previous understanding of adequate dosing is way off the mark. In this FX Medicine podcast Professor Michael Holick is interviewed on the latest evidence in support of higher dosing of vitamin D and the most recently identified health implications for deficiency.