Background:The role of dietary salt consumption in the etiopathogenesis of Rheumatoid Arthritis (RA), and autoimmune disease in general, has received renewed interest. This has been fueled by the increased prevalence of autoimmune disease worldwide correlating with western diets and heightened consumption of salt rich foods and also studies at the cellular level demonstrating induction of IL 17 producing T helper cells (Th17) by dietary salt.Objectives:To conduct a narrative review of observational studies and clinical trials on the role of dietary salt as an environmental risk factor for the onset and development of RA.Methods:A comprehensive search was done of the literature from 2010 to 2021, using the search terms dietary salt and RA; the native interfaces EBSCO and Ovid were used. Databases searched included Pubmed, Embase, EMCare, Medline and CINAHL using a Population, Exposure and Outcome framework; the MESH terms RA, risk factors, nutrition and salt were used. Data was extracted by an independent reviewer.Results:Out of the 72 studies initially identified, 50 were included in this review. Studies in murine models have demonstrated that high concentrations of sodium chloride promote the differentiation of T helper lymphocytes, via the serum- and glucocorticoid- inducible kinase 1 (SGK1) mediator towards the proinflammatory Th17 driven immune response. Six studies were carried out in human subjects. Study design ranged from cross sectional observational to nested case control studies. Sodium intake amongst participants characterized as having high intake, or being placed in the higher quartiles, ranged from 4.5-5grams per day. 5 out of 6 studies demonstrated that increased dietary salt consumption is associated with earlier onset RA. One study suggested an association between high salt intake and erosive disease at diagnosis and the development of anti-citrullinated protein antibodies (ACPA), although evidence was weak and from a single study only. Another study found that increased consumption of salt was only associated with risk of RA in smokers, highlighting the need to explore confounding variables further.Conclusion:This narrative review of the literature provides some evidence that supports a role of excess dietary salt consumption as a risk factor for the onset and severity of RA.Disclosure of Interests:None declared
Effect of methotrexate on circulating T-helper subsets in rheumatoid arthritis
