Nutrition in Rheumatoid Arthritis

NUTRA population and recruitment. Approximately 120 women and men aged 18-85 years with diagnosed RA will be recruited in the Gothenburg region. Approximately 42-48 evaluable participants per randomized group provide 80% power to detect a 15% between-group difference in ApoB after three months at a two-sided α=0.05. Stable treatment and no planned changes in antirheumatic or lipid-affecting medication during the primary period limit pharmacological confounding. Recruitment follows established rheumatology pathways; detailed eligibility criteria are governed by the approved protocol.

Randomization and intervention. Participants are randomized to an immediate three-month intervention or a waiting-list control for three months before receiving the same dietary intervention. The intervention follows NNR2023 and combines food provision with structured, individualized support to facilitate sustainable change. The waiting-list design preserves a randomized comparison while ensuring that all participants are offered the intervention.

Data collection. Baseline and three-month assessments include fasting blood samples, clinical phenotype, blood pressure, joint examination, body composition by dual-energy X-ray absorptiometry, physical function and quality-of-life questionnaires, weighed dietary records and a Food Frequency Questionary (FFQ). Adherence is evaluated from dietary data and selected biomarkers. Samples are stored for metabolomics and inflammatory profiling. The simplified six-month after intervention end follow-up consists of fasting routine blood lipids only, minimizing participant burden while retaining a clinically meaningful maintenance outcome.

Outcomes and analysis. ApoB is the primary outcome. Secondary outcomes include LDL and HDL cholesterol, triglycerides, total cholesterol, disease activity measured by the Disease Activity Score in 28 joints using erythrocyte sedimentation rate (DAS28-ESR), and European Alliance of Associations for Rheumatology (EULAR) response and remission. Olink Target 96 Inflammation characterizes inflammatory profiles; metabolomics supports exploratory response and predictor analyses. The primary analysis follows intention-to-treat principles, comparing randomized groups at three months with baseline adjustment. Mixed-effects models will account for repeated measurements where appropriate. Inflammatory analyses will address multiple testing. Predictor analyses will be exploratory, with model complexity constrained by sample size and internal validation used to assess overfitting.