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Objectives: This study aimed to assess the relationship between dietary intake and disease outcomes in patients with radiographic axial spondyloarthritis (r-axSpA), focusing on inflammation and disease activity, while also evaluating other health outcomes, and to compare dietary intake between patients and controls.

Method: In a cross-sectional analysis, we studied 295 patients with r-axSpA (modified New York criteria for ankylosing spondylitis) in northern and south-western Sweden. Of these, 155 were of similar age to controls (50–64 years) from the Swedish CArdioPulmonary bioImage Study (SCAPIS) and were matched on sex, age, and geographical location to 604 controls. Dietary intake was evaluated using the MiniMealQ food frequency questionnaire. Differences in dietary intake between patients and controls were assessed in conditional logistic regression models. Nutrients with significant group differences were examined in patients (n = 295) by regression models for the outcomes Ankylosing Spondylitis Disease Activity Score with C-reactive protein (CRP) (ASDAS) and CRP.

Results: Patients had a lower dietary fibre density, as well as lower intake of marine omega-3 fatty acids, calcium, folate, iodine, phosphorus, potassium, selenium, vitamins A, C, and K, β-carotene, and alcohol. Low intake of marine omega-3 fatty acids was associated with a higher ASDAS, and a lower dietary fibre density was associated with elevated CRP.

Conclusions: Patients with r-axSpA report lower dietary quality compared with controls. Dietary intake is related to disease activity and inflammation. Further exploration of metabolic biomarkers and disease outcomes is warranted, and the impact of a health-promoting dietary intervention should be assessed.