The effects of synbiotics surpass prebiotics in improving inflammatory biomarkers in children and adults: A systematic review, meta-analysis, and meta-evidence of data from 5207 participants in 90 randomized controlled trials

Several trials have revealed the beneficial effects of synbiotics on inflammatory biomarkers. Nevertheless, the findings drawn from extant trials remain contentious. This meta-analysis evaluated the effects of synbiotics and prebiotics on inflammatory and anti-inflammatory biomarkers in children and adults. We searched PubMed, Embase, Cochrane, Scopus, and Web of Science until February 2024 for randomized controlled trials (RCTs) regarding synbiotic supplementation for inflammation biomarkers. The GRADE approach was applied to assess the quality of evidence, and the Cochrane risk-of-bias (RoB) tool was used to evaluate study quality. Ninety RCTs with 5207 participants were included in the meta-analysis. Finding revealed that biotic supplementation could significantly improve CRP (Synbiotics; SMD = -0.51; 95 % CI: -1.00, -0.03, P = 0.036, and prebiotics; SMD = -0.81; 95 % CI: -1.51, -0.10, P = 0.026), hs-CRP (Synbiotics; SMD = -0.66; 95 % CI: -0.96, -0.37; P < 0.001, and prebiotics; SMD = -0.50; 95 % CI: -0.86, -0.15; P = 0.006), TNF-α (Synbiotics; SMD = -0.70, 95 % CI: -1.16, -0.23; P = 0.003, and prebiotics; SMD = -0.57, 95 % CI: -0.93, -0.21; P = 0.002), IL-1β (Synbiotics; SMD = -1.35; 95 % CI: -2.44, -0.27, P = 0.014, and prebiotics; SMD = -0.44; 95 % CI: -0.76, -0.12, P = 0.006), and IL-6 (Synbiotics; SMD = -2.02, 95 % CI: -2.86, -1.18; P < 0.001, and prebiotics; SMD = -0.41, 95 % CI: -0.80, -0.03; P = 0.036) in adults. In contrast, synbiotics failed to show beneficial effects in children. However, in adults, prebiotics illustrated a significant reducing effect on IL-8 (SMD = -1.47, 95 % CI: -2.68, -0.26; P = 0.011). Overall, supplementation with synbiotics and prebiotics beneficially improved adult inflammatory biomarkers. However, based on subgroup analysis, our results revealed a significant reduction in inflammatory biomarkers following synbiotics administration in short-term supplementation (<10 weeks) among adults.