Effect of Dietary Fiber Intake on Chronic Low-Grade Inflammation in Children and Adolescents: A Systematic Review and Meta-analysis of Randomized Controlled Trials.

Previous research suggests that dietary fiber (DF) intake may help reduce chronic low-grade inflammation (CLGI), a condition linked to the early development of cardiometabolic risk factors. Childhood and adolescence represent critical periods for preventing noncommunicable diseases, when adopting healthy eating habits, including adequate fiber consumption, could effectively control CLGI. However, the evidence on DF's impact on CLGI in the pediatric population remains inconsistent and has not been comprehensively reviewed in a single article. Therefore, we aimed to conduct a systematic review and meta-analysis to assess the effect of DF intake on CLGI in children and adolescents. A systematic search was performed in 4 databases up to January 2025. Two reviewers screened 2030 studies based on inclusion criteria: randomized controlled trials involving participants ≤18 y, interventions (Is) with any type of DF (supplementation, fiber-rich foods, or fiber intake advice) and reporting serum CLGI markers, including C-reactive protein (CRP), interleukin (IL)-6 and TNF-α, among others. Twenty-five randomized controlled trials were included in the systematic review, which showed that DF may have beneficial effects on CRP, IL-10, adiponectin, IL-1β, and IL-6 concentrations; though findings were inconsistent, with some studies reporting no significant changes. Meta-analysis was conducted for CRP, IL-6, and TNF-α. Meta-analysis for CRP concentrations included 10 studies and revealed a significant decrease following DF Is compared to controls (mean difference: -0.640; 95% CI: -1.075, -0.204). Meta-regression revealed that Is based on fiber supplementation resulted in significantly greater CRP reductions compared to those involving fiber-rich foods. Meta-analysis for IL-6 and TNF-α concentrations showed no significant effect after DF I. In conclusion, this review provides evidence that fiber Is may have a beneficial impact on certain markers of CLGI in children and adolescents, particularly by reducing serum CRP concentrations. However, the findings also reveal inconsistencies in the effects of fiber intake on other inflammatory markers. This trial was registered at PROSPERO as CRD42024516794.