I will start this lecture by describing briefly the conventional and non-conventional health effects of vitamin D. Next I go though the etiology of type 1 diabetes, aiming to help you to understand in very simple terms why we could expect vitamin D to affect diabetes risk and what kind of factors make it difficult to investigate the risk factors. The next section goes through the limited number of studies investigating these associations and in the final part of this lecture I suggest two frameworks for the putative public health importance.

Throughout the lecture, I will use ‘vitamin D’ as a general term, without attempting to differentiate specific dietary or metabolic forms. As the etiology of type 1 diabetes as well as the range of vitamin D action are only partly understood, I decided to keep this review at a relatively general level, without including detailed hypotheses on mechanisms.

On the whole, my aim is to rise questions rather than to attempt to answer them. At the end of this lecture, I feel you will have understood the most important things, if you find yourself (as happened to me) being surprised about how little we actually know, but at the same time also understanding the reasons for this.