Nutrition in Rheumatic Diseases

Background: Patients with inflammatory rheumatic diseases (IRD) are prone to malnutrition for several reasons. The diseases and treatment can cause reduced intake and absorption of nutrients and the inflammatory processes may cause an increased demand for nutrients, especially proteins. Studies report that nutritional status can affect disease activity. Dietary supplement of 3-4 gram omega-3 has shown beneficial effect upon disease activity in patients with IRD.

Aim: To investigate whether improved dietary intake with and without supplements of omega-3 will affect disease activity in patients with rheumatoid arthritis (RA) and spondyloarthritis (SpA).

Hypothesis 1: A systematic change of diet in line with the Norwegian dietary guidelines, which will result in increased intake of, among other nutrients, omega-3 fatty acids and complete protein, as well as reduced intake of saturated fat and sugar, will improve nutritional status and reduce disease activity.

Hypothesis 2: A systematic change of diet (as above), included a high dose of omega-3 will further improve nutritional status and reduce disease activity compared with placebo.

Design: A DB-RCT-study will be conducted. All patients will receive individualized dietary guidance by a clinical dietician for 12 weeks, before randomization to supplements of omega-3 or placebo, for 24 weeks. The supplement will be blinded for the participants, researchers and physicians.

Clinical implications: The study will investigate the effect of improved diet and nutrition on treatment offered to patients with IRD to provide more evidence-based knowledge, and thus specific dietary guidelines for patients with IRD. In addition, the study might increase the understanding of the role of omega-3 in the pathogenesis of inflammation.

The study is approved by the Regional Committee for Medical and Health Research Ethics. Participation is voluntary, and informed consent will be requested. Outpatients will be recruited by doctors at the Rheumatology Department at Haukeland University Hospital (HUH). Patients recruited will be included consecutively. The recruitment period will last up to 12 months. Anthropometrical measurements, analysis of body composition, blood tests, clinical parameters, and dietary data will be collected at baseline, and after 12, 24, 36 and 52 weeks.

Eligibility Criteria:
Inclusion Criteria:

* Patients must be diagnosed with one of the following diagnoses: rheumatoid arthritis, according to the ACR / EULAR 2010 criteria, psoriatic arthritis, according to the CASPAR criteria, axial spondylarthritis, including ankylosing spondylarthritis and non-radiographic spondylarthritis, according to the ASAS criteria
* Duration of illness ≥0.5 years
* Between 18 and 75 years
* Understand Norwegian
* The patient has given informed consent to participate
* No change in medication the last 12 weeks before inclusion

Exclusion Criteria:

Diagnoses / conditions that make it difficult to follow a dietary intervention and / or supplementation of omega-3s, including:

* Conditions or use of medications where omega-3 is contraindicated
* Pregnancy / lactation
* Allergy to soy or fish
* Severe liver disease
* Severe mental or physical illnesses, such as insulin-requiring diabetes