Extraskeletal actions of vitamin D

The document from July 1, 2016, reviews the wide-ranging extraskeletal actions of vitamin D, including its roles in cancer prevention and treatment, cardiovascular health, diabetes mellitus type 2, obesity, muscle function, skin health, and immune function. It emphasizes that vitamin D receptors (VDR) and the enzyme CYP27B1 are present in nearly all cells, indicating potential widespread effects of vitamin D. The review details how vitamin D can inhibit cancer cell proliferation and metastasis, with mixed results from clinical studies on its effectiveness in preventing various cancers. It also discusses vitamin D's role in cardiovascular health, with animal studies suggesting benefits but human trials showing inconsistent results. In terms of diabetes and obesity, vitamin D is implicated in insulin secretion and adipogenesis, but clinical trials have not conclusively supported its use in treatment or prevention. The document also notes vitamin D's importance in muscle function and fall prevention, with mixed outcomes from supplementation trials. For skin health, vitamin D is involved in keratinocyte proliferation and differentiation, with therapeutic uses in psoriasis but less conclusive results for other skin diseases. The review highlights vitamin D's complex role in modulating both adaptive and innate immunity, with potential benefits for autoimmune diseases and organ transplant rejection, but mixed effects on allergic diseases and infections. Despite the promising preclinical findings, the document acknowledges the challenges in translating these into successful clinical outcomes and the need for further research, particularly large randomized controlled trials, to fully understand the efficacy of vitamin D supplementation in these areas.