Association between diet and treatment results in patients with rheumatoid arthritis and systemic lupus erythematosus

Abstract: Rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) are chronic autoimmune inflammatory diseases. The causes of these diseases are unknown and evidence indicates that a combination of both genetic and environmental factors contribute to their etiology. Several studies have reported dietary benefits for patients with RA as well as SLE. Nevertheless, many of these studies have mainly focused on the dietary impact on the disease status, and the affect on treatment has not often been considered. The majority of patients with RA and SLE are dependent on treatment. Therefore, the dietary aspects in regards to treatment need to be explored further. Thus, the aim of this thesis was to examine the association between diet and treatment results in patients with RA and SLE. This thesis included five papers (Papers I-V) and was based on data of participants from three registers; Epidemiological Investigation of Rheumatoid Arthritis (EIRA), SLE Vascular Impact Cohort (SLEVIC) and Swedish Mammography Cohort (SMC). All participants from EIRA, SLEVIC and SMC were asked to complete food frequency questionnaires (FFQ) regarding their dietary habits. Dietary data from completed FFQ were linked with clinical data obtained from either Swedish Rheumatology Quality register (SRQ) or medical records. The associations between diet and clinical outcomes were analyzed with logistic regression and prospective dietary changes were analyzed with mixed models and cluster analysis. The main results of this thesis showed that 1) vitamin D and omega-3 fatty acids (FA) were associated with better response to treatment in RA patients, 2) beta-carotene (antioxidant), linoleic acid (omega-6 FA) and vitamin B6 were inversely associated with increased doses of glucocorticoids in SLE patients, 3) women who have been diagnosed with RA did not remarkably change their diet due to their disease, 4) omega 3 FA was inversely associated with non-inflammatory pain after anti-rheumatic treatment in RA patients and 5) riboflavin, phosphorus, selenium and thiamin were inversely associated with carotid plaque in SLE patients. Results from this thesis presented several associations between specific dietary nutrients and clinical outcomes of RA and SLE, in particular concerning treatment results. In summary, diet may play a role in response to anti-rheumatic treatment in patients with RA and SLE.