INFECTIONS AND ENVIRONMENTAL ASPECTS OF AUTOIMMUNITY: Edited by Yehuda ShoenfeldVitamin D and rheumatoid arthritis: an ongoing mysteryBragazzi, Nicola L.a,∗; Watad, Abdullab,c,d,∗; Neumann, Shana G.d; Simon, Michaeld; Brown, Stav B.d; Abu Much, Arsalanb,d; Harari, Adamd; Tiosano, Shmuelb,d; Amital, Howardb,c,d; Shoenfeld, Yehudac,dAuthor Information aSchool of Public Health, Department of Health Sciences (DISSAL), University of Genoa, Genoa, Italy bDepartment of Medicine B cZabludowicz Center for Autoimmune Diseases, Sheba Medical Center, Tel Hashomer dSackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel Correspondence to Professor Yehuda Shoenfeld, MD, FRCP, MaACR, Zabludowicz Center for Autoimmune Diseases, Sheba Medical Center (Affiliated to Tel-Aviv University), Tel-Hashomer 5265601, Israel. Tel: +972 3 535 2855; fax: +972 52 666 9020; e-mail: [email protected] Current Opinion in Rheumatology: July 2017 - Volume 29 - Issue 4 - p 378-388 doi: 10.1097/BOR.0000000000000397 Buy Metrics Abstract Purpose of review In recent years, there has been a growing interest in the value of vitamin D and its effects on autoimmunity. The aim of this review is to summarize the current knowledge on the association between vitamin D and rheumatoid arthritis (RA) in terms of prevalence, disease activity, clinical expression, serology and gene polymorphisms of vitamin D receptors. Recent findings Studies have shown contrasting findings concerning the association between vitamin D levels and RA. Vitamin D seems to have immunomodulatory properties. Therefore, low vitamin D levels could contribute to increased immune activation. However, the potential role of vitamin D supplementation in preventing RA manifestation and its beneficial role as a component of RA treatment remain controversial. The relationship between RA susceptibility and vitamin D polymorphisms is also unclear. Summary Despite advancements synthesized by some recent meta-analyses, the relationship between vitamin D and RA requires further evaluation. Further research is needed to confirm the relationship between RA susceptibility and vitamin D polymorphisms and to determine whether vitamin D plays a role in preventing the manifestation of RA. Finally, additional studies are required to determine the impact and optimal amount of vitamin D supplementation in the treatment of RA patients. Copyright © 2017 Wolters Kluwer Health, Inc. All rights reserved.