Evaluation of the relationship between dietary inflammatory index and some biochemical parameters and disease activity in patients with rheumatoid arthritis

The purpose of this study was to investigate the relationship between dietary inflammatory index (DII) calculated from daily nutrient intake and rheumatoid arthritis disease activity. The study was conducted with 63 individuals aged 22-75 years, who were diagnosed with rheumatoid arthritis (RA) before and applied to Başkent University Ankara Hospital Rheumatology Outpatient Clinic between February and April 2021. Data were collected with a questionnaire to determine the sociodemographic characteristics and general information about the disease. Anthropometric measurements were taken from the participants and biochemical parameters were evaluated. Dietary inflammatory index was calculated based on the daily nutrient intakes from the individuals' three-day food records. Dietary inflammatory index scores of individuals were divided into three groups (tertiles). Accordingly, DII scores were ≤-1.04 in the 1st tertile, -0.88 to 0.72 in the 2nd tertile and DII ≥ 0.97 in the 3rd tertile. An increase in the numerical value of tertiles means an increase in the inflammatory load of the diet. Therefore, the first tertile represents an anti-inflammatory diet, and the third tertile predicates a pro-inflammatory diet. The median DII score was -0.03 [2.8] and limit range is between -4.21 and 3.30. There was no significant differences between the age, body mass index, waist circumference, waist/hip ratio, waist/height ratio, triceps skinfold thickness, middle upper arm circumference, hand grip strength, smoking status and drug treatments of the patients across DII tertiles (p>0.05). A significant difference was found between serum 25-OH Cholecalciferol levels and DII tertiles (p<0.05). In addition, there was a statistically significant correlation between serum C-reactive protein (CRP) levels and total DII score (p<0.05). Individuals in the first tertile consume dietary fiber, polyunsaturated fatty acids and omega 3 fatty acids more than individuals in the third tertile (p<0.05). It was also determined that the group with low DII score had higher dietary intake of vitamin E, vitamin C, thiamine, niacin, vitamin B6, folate, magnesium and iron than the group with high DII score (p<0.05). No significant relationship was found between anthropometric measures and disease activity (p>0.05). However a significant correlation was found between hand grip strength and disease activity (p<0.05). Regarding DII score, there was a statistically significant difference between DII tertiles and DAS28 CRP (p<0.05). A statistically significant association was found between DII score and disease activity (p<0.05). In conclusion, it is thought that reducing the inflammatory load of the diet will contribute to maintaining low disease activity patients with rheumatoid arthritis.