RT Journal Article SR Electronic T1 Vitamin D – what is normal according to latest research and how should we deal with it? JF Clinical Medicine JO Clin Med FD Royal College of Physicians SP 171 OP 174 DO 10.7861/clinmedicine.16-2-171 VO 16 IS 2 A1 Neil JL Gittoes YR 2016 UL http://www.rcpjournals.org/content/16/2/171.abstract AB Vitamin D deficiency is a public health concern. Mediated by classical endocrine effects, vitamin D deficiency is causally linked with bone and calcium disorders. Non-endocrine actions of vitamin D are also widely recognised and these effects are mediated by local tissue activation of vitamin D bringing about intracrine effects in non-classical sites. Supported by large volumes of observational studies linking low circulating vitamin D with negative outcomes for many common disease states, there is growing interest that vitamin D may be central to the pathology and outcomes of many common diseases, including cardiovascular, cancer and autoimmune conditions. This article explores the quality of evidence linking vitamin D and various disease outcomes, and furthermore describes some of the cellular and molecular mechanisms of vitamin D action that may help explain some of the incongruity of data observed in observational versus interventional studies of vitamin D supplementation.