For decades, population studies have revealed a shocking number of diseases associated with vitamin D insufficiency. However, recent vitamin D supplementation trials have failed to produce the same benefits. The reason for this disparity stems from the fact that measuring vitamin D concentration in the blood is really only a way to measure sun exposure. The mistake often made is to assume health outcomes associated with this biomarker can be achieved regardless of how it is elevated. In population studies, more than 90% of vitamin D measured in the blood is made from the sun. Since sun exposure produces more than a dozen important hormones and peptides along with vitamin D, it is not surprising that supplementation trials providing only one isolated component are rendering different results. In fact, a growing number of studies are finding benefits of sun exposure independent of vitamin D production.