Comparing effects of low glycemic index/high-fat, high-calorie diet and high-fat, high-calorie diet on cytokine levels of patients with cystic fibrosis: A randomized controlled clinical trial.

The importance of the host inflammatory response, as a central pathological feature of cystic fibrosis, is well recognized. Additionally, hyperglycemia can induce an immune response and consecutively may exacerbate symptoms of this disease. Hence, adherence to a low glycemic index diet, through normalizing blood glucose levels, may reduce inflammation in patients with this disease. This study aimed to compare effects of a low glycemic index/high-fat, high-calorie diet and routine high-fat, high-calorie diet on inflammatory biomarkers in patients with cystic fibrosis. In this randomized clinical trial, 44 children and adolescents with cystic fibrosis were randomly assigned to receive for three months either a high-fat, high-calorie diet (n = 22) or a low glycemic index/high-fat, high-calorie diet (n = 22) with similar calorie and macronutrients composition to the control diet. Patients in first arm were allowed to use all sources of carbohydrates with different glycemic indices, whereas those in another arm consumed carbohydrates from low glycemic index sources. Serum levels of the pro-inflammatory cytokines IL-6, IL-17A, and IFNγ, and the anti-inflammatory cytokine IL-10 were measured at baseline and after the end of the trial. There were significant differences between groups for IL-6 (P = 0.02) and IL-17 (P = 0.01), in favor of the low glycemic diet, but no between-group differences were detected in IL-10 and IFN-γ. Although serum levels of IL-17 were reduced in both the groups as compared with the baseline values, this reduction was only significant in the group assigned to the low glycemic diet (P= 0.007), In addition, IL-6 serum levels decreased and those of IL-10 increased significantly as compared with the baseline values in the low glycemic diet (P= 0.01). It seems that adherence to a low glycemic index/high-fat, high-calorie diet for three months can improve some inflammatory biomarkers in children and adolescents with cystic fibrosis compared with the high-fat, high-calorie diet.