Vitamin D deficiency: universal risk factor for multifactorial diseases?

In the Western world, the majority of morbidity and mortality are caused by multifactorial diseases. Some risk factors are related to more than one type of disease. These so-called universal risk factors are highly relevant to the population, as reduction of universal risk factors may reduce the prevalence of several types of multifactorial disease simultaneously. Vitamin D deficiency is traditionally seen as an etiological factor in bone disorders such as rickets and osteomalacia. Recent studies also suggest a role for vitamin D deficiency in multifactorial disorders, including progressive renal function loss and cardiovascular disease; it is also a risk factor for frailty. The potentially pleiotropic effects of vitamin D analogues support the hypothesis that vitamin D deficiency is a universal risk factor. Here we review molecular actions of the vitamin D receptor (VDR), to identify mechanisms and pathways for vitamin D deficiency as a universal risk factor. To identify genes directly regulated by the VDR, we searched for genes containing vitamin D response elements (VDREs). A further refinement was made by selecting only VDRE-containing genes with documented modulation by VDR analogues in vivo. Our search yielded a limited number of factors possibly related to pleiotropic effects of vitamin D, including growth factors, hormones, inflammatory factors and factors related to calcium homeostasis. Results from observational, intervention and mechanistic studies indicate that vitamin D is a universal risk factor involved in diverse multifactorial conditions. Further exploration of the multifaceted actions of vitamin D may pave the way for disease-overriding intervention strategies.