The Future of Vitamin D: Extraskeletal Effects

This review highlights current Russian and international scientific data on the role of vitamin D in a wide range of physiological processes, with a special emphasis on its extraskeletal functions, clinical implications, and manifestations. A search and analysis of the medical scientific data from 2004 to 2023 was undertaken using the databases eLibrary.RU, the Russian National Library, and the Fundamental Library of the S.M. Kirov Military Medical Academy, and the international search platforms PubMed and Medscape. Key scientific publications were reviewed, including outcomes from preclinical studies on laboratory animals utilizing vitamin D supplements and clinical studies involving patients with vitamin D deficiency. It examines vitamin D metabolism and its involvement in the immune function, as well as in the cardiovascular, respiratory, digestive, endocrine, nervous, reproductive, and other systems. Vitamin D deficiency is clearly reflected in the development, pathogenesis, and progression of diverse prevalent human diseases, including infectious, chronic inflammatory, allergic, systemic autoimmune, and various neoplastic conditions. The article highlights key historical milestones in the discovery of vitamin D and its metabolites, their health impacts, and the role of vitamin D deficiency in disease development. Preclinical and clinical studies have largely validated the effects of vitamin D at the cellular, tissue, and organ levels, including its role in regulating the function of various physiological systems as well as cellular proliferation and differentiation. Numerous long-term prospective studies are ongoing, linking low vitamin D levels to a wide spectrum of human diseases. This continues to generate considerable scientific interest and enthusiasm for exploring the effects of dietary vitamin D supplementation on human health, despite inconsistent results from clinical studies.