Pakistan Journal of Nutrition 11 (3): 293-300, 2012 ISSN 1680-5194 © Asian Network for Scientific Information, 2012 293 Relationship Between Vitamin D and Rheumatoid Arthritis Disease Firas Sultan Azzeh Department of Clinical Nutrition, Faculty of Applied Medical Sciences, Umm Al-Qura University, P.O. Box 7067, Makkah, Saudi Arabia Abstract: Rheumatoid arthritis is a chronic inflammatory disease in which the synovial membrane of the joint becomes inflamed, resulting in a swelling, stiffness, pain, limited range of motion, joint deformity and disability. Vitamin D is the "sunshine vitamin" which is converted in the body to a hormone 1, 25- dihydroxyvitamin D3 by the photolytic action of ultraviolet light on the skin. Vitamin D plays an important role, along with the essential minerals calcium and phosphorus, in the maintenance of healthy bones and teeth. An inverse association between vitamin D intake and rheumatoid arthritis was found in some prospective studies. Although vitamin D has been implicated in a decreased risk of autoimmune diseases such as type 1 diabetes and multiple sclerosis, its role in decreasing the risk of rheumatoid arthritis remains equivocal. This scientific review is written to illustrate the possible relationships between rheumatoid arthritis and vitamin D. Key words: Rheumatoid arthritis, vitamin D, Vitamin D Receptors (VDR) INTRODUCTION Arthritic conditions encompass more than 100 different diseases and conditions affecting the joints, the tissues surrounding the joints and the connective tissue. Arthritic conditions are among the most common diseases in the world and include osteoarthritis, Rheumatoid Arthritis (RA) and gout (Rizzo, 2005). Arthritic conditions affect nearly one in sex North Americans and are the leading cause of disability among Americans 18 years of age and older (U.S. Department of Health and Human Services, 2001) and about 22% of U.S. adults have arthritis (ACR, 2010). Common misconceptions about arthritic conditions are they only affect older persons, that they are an inevitable consequence of aging, they are diagnosed in people of all ages, including children and teens (Lee, 2007). Juvenile RA affects 70.000 to 100.000 children in US and is one of the most common chronic conditions of childhood (Rizzo, 2005). There are several factors known to increase the risk of arthritic conditions, three of which are modifiable: overweight, joint injuries and infections. Non-modifiable risk factors include female sex, age and family history (Rizzo, 2005). RA is an autoimmune disease, in which a person's immune system attacks his or her own healthy tissues (Lee, 2007). RA is the most common inflammatory arthritis across the world. Although the etiology of RA remains a mystery, a variety of studies suggest that a blend of environmental and genetic factors are responsible and both affecting the prevalence of autoimmune disease (Turhanoglu et al., 2010). Vitamin D is the "sunshine vitamin" which is converted in the body to a hormone 1, 25-dihydroxyvitamin D3 by the photolytic action of ultraviolet light on the skin. Vitamin D plays an important role, along with the essential minerals calcium and phosphorus, in the maintenance of healthy bones and teeth (Combs, 1988). Moreover vitamin D sufficiency, especially during the childhood and adolescent years, is critically important not only for bone health, but also for the prevention of many serious chronic diseases, including cancer, cardiovascular heart disease and autoimmune diseases. It has been suggested that vitamin D deficiency during infancy and childhood may imprint an increased risk of these chronic diseases for the rest of one's life (Holick, 2006). An inverse association between vitamin D intake and RA was found in the prospective cohort study done by the Iowa Women’s Health Study (Merlino et al., 2004). Vitamin D is a hormone essential for bone and mineral homeostasis and is also involved in the regulation of cells in the innate and adaptive immune system through the Vitamin D Receptor (VDR) as a suppressor of pro- inflammatory responses (Mathieu et al., 2001). Although vitamin D has been implicated in a decreased risk of autoimmune diseases such as type 1 diabetes and multiple sclerosis, its role in decreasing the risk of RA remains equivocal (Hypponen et al., 2001; Holick, 2007). The aim of this review is to summarize the currently available information for the effect of vitamin D on RA disease. Rheumatoid arthritis Introduction: The name (RA) is based on the term" rheumatic fever", an illness which includes joint pain and is derived from the Greek word rheumatos ("flowing"). The suffix-oid ("resembling") gives the translation as joint inflammation that resembles rheumatic fever. The first recognized description of rheumatoid arthritis was made in 1800 by Dr. Augustin Jacob Landré-Beauvais (1772-1840) of Paris (Landre- Beauvais, 2001).