Diet for chronic inflammatory diseases
Short description
Many patients with chronic inflammatory diseases such as rheumatoid arthritis (RA) have persistent disease activity despite drug treatment. Therefore, it is not uncommon for those affected by rheumatism to try to improve their situation themselves, for example through diet and exercise. Unfortunately, knowledge about specific diets for people with rheumatism is very limited and therefore general dietary advice is referred. Through a number of intervention studies, we have investigated the effect the diet can have on this patient group. Our research aims to increase knowledge about specific diets for people with rheumatism.
PIRA – Postprandial Inflammation in Rheumatoid Arthritis
The primary purpose of PIRA (Postprandial Inflammation in Rheumatoid Arthritis) was to study what happens in the body during the hours following a meal with different food compositions in patients with rheumatoid arthritis (RA).
In the study, we compared a meal with red meat (beef and pork) to a meal with fatty fish (salmon) and a vegan meal (soy protein). Each participant consumed all three meals as their first meal of the day, with one week between each, thus being compared to themselves in a crossover design. Additionally, the study compared individuals with RA to those without RA to see if there is a difference in their reactions to a meal with red meat.
The study was conducted in two rounds (due to COVID-19) during 2020 and 2021. A total of 25 women with RA and 29 women without RA participated in the study.
The primary outcome of the study was the inflammatory marker IL-6, which increases after meal intake, but there was no difference in the magnitude of the increase after the three different meals. However, there was a difference in how blood lipids were affected. After the meal with fatty fish, compared to both red meat and soy protein, the number of very low density lipoprotein (VLDL) particles and the fat content in VLDL-4 particles increased.
Metabolites in the blood measured with Nuclear Magnetic Resonance (NMR) showed no differences in concentrations between women with or without RA. However, one metabolite, phenylalanine, was higher in both fasting and postprandial samples among women with RA. The cause of this is unknown.
Further from the study, we will examine whether the meals have different impacts on which genes are expressed immediately after a meal, i.e., which potential inflammatory or cardiovascular-related molecules are affected.
ADIRA – Anti-inflammatory Diet In Rheumatoid Arthritis
The main purpose of the ADIRA study was to try to reduce disease activity in patients with RA through a proposed anti-inflammatory diet, containing lots of fruits, vegetables, whole grains, fish, probiotics, and healthy fats.
The ADIRA study, like the MIRA study, used a crossover design, meaning each individual consumed both the intervention and control diets and was therefore compared to themselves. The study was conducted during 2017-2018. A total of 50 RA patients were randomized to start with either the intervention or control diet for 10 weeks. After a four-month washout period, they switched diets. Participants received food corresponding to about 50% of their daily energy needs delivered via meal kits and were encouraged to consume the same type of food otherwise. Patients continued their current medication treatment throughout the study.
The primary outcome in ADIRA was disease activity measured as the Disease Activity Score 28 (DAS28). Secondary outcomes included inflammatory markers, lipoprotein profile, and questionnaires capturing quality of life and health. In the main analysis, a linear mixed ANCOVA model of DAS28 for the 47 patients who completed at least one full diet period, there was no significant difference between the diets. However, disease activity significantly decreased during the period with the anti-inflammatory diet, which it did not during the control diet period. In analyses including those who completed the entire study, differences between the diets were significant for DAS28. Among participants with high adherence and no medication changes, erythrocyte sedimentation rate (ESR), and inflammatory markers C-X-C motif ligand 1 (CXCL1), CXCL5, CXCL6, and tumor necrosis factor ligand superfamily member 14 (TNFSF14) were lower after the intervention diet compared to the control diet.
Additionally, the intervention diet positively affected blood lipids, where triglycerides and HDL improved after the intervention compared to the control. Moreover, the profile of triglycerides, cholesterol esters, and phosphatidylcholine, among other lipids, improved. However, we could not demonstrate any significant effect on health-related quality of life in the study.