Vitamin D in Health and Disease

Vitamin D (VD) is a lipo-soluble hormone that is well known for its effects on calcium homeostasis and bone metabolism. Recently, there has been growing interest in the extra-skeletal effects of VD. In particular, recent studies have highlighted how VD plays a fundamental role in immunomodulation processes in the context of both innate and adaptive immunity, with consequential anti-inflammatory and antioxidant effects in different immune-mediated pathologies, such as systemic sclerosis, psoriasis, atopic dermatitis and rheumatoid arthritis, as well as in various pro-inflammatory processes affecting the airways. Recent evidence has shown that VD is also closely related to other components such as the microbiome, with which it appears to be interconnected in the pathophysiology of many allergic diseases. In addition to the known immunomodulatory effects of VD, several studies have reported that it is also endowed with important anti-proliferative, anti-angiogenic and pro-differentiative effects in cancer thanks to its effects on the modulation of the expression of tumor miRNAs through its action at the VD receptor (VDR) level. In view of this, it is clear that VD supplementation represents a safe and valid therapeutic strategy that is capable of improving the clinical outcome of many diseases.

In this Special Issue, the different functions and potential benefits of VD, some pathological manifestations related to VD deficiency, the therapeutic potential of VD supplementation, and the link between the effects of VD and the microbiome were discussed.