There is no shortage of ailments that vitamin D has been claimed to prevent or cure - various types of cancers, heart disease, COVID-19, diabetes, an assortment of autoimmune conditions, just to name a few. What is it about this micronutrient that leads people to behold it as a panacea? In this episode, we sift through what we know about the biology of vitamin D, along with what happens when you don’t have enough of it, in an attempt to discern what might be overhype and what might be underhype when it comes to vitamin D and health claims. And there certainly is ample reason for excitement over this micronutrient, as its deep, deep evolutionary history reveals just how many biological processes in which vitamin D is intimately and vitally involved. The consequences of vitamin D deficiency form a large part of its human history, as soaring rates of rickets during the Industrial Revolution drew the interest of researchers intent on pinpointing the cause of this disease. As is typical for this podcast, the more we know, the more questions we have, like “who decided what counts as deficiency?”, “how much vitamin D should people be getting?”, and “what is vitamin D really telling us?”. Tune in for plenty of sunshine, cod liver oil, and drama over vitamin D.