Role of vitamin D in acquired immune and autoimmune diseases

Vitamin D has been attributed roles in the pathogenesis and prevention of several diseases such as cancer, cardiovascular disease, multiple sclerosis, diabetes, autism and autoimmune diseases. The concomitant expression of the 25-hydroxyvitamin D3-1α-hydroxylase and of the vitamin D3 receptor in animal and human tissues and organs other than bone supports this paradigm. Translated into the clinical field, meta-analyses and systematic reviews have also revealed an association between vitamin D insufficiency or deficiency and non-osseous diseases. Although relying on the large databases, they are diverse in nature and involve participants of varying age and evolving in different environments. Furthermore, they do not allow any analysis of a possible causal relationship between vitamin D supplementation and clinical outcomes. Following a brief historical account, this review addresses these caveats, and gives examples of randomized controlled trials conducted in the fields of acquired immune and autoimmune diseases.