Children with autism spectrum disorder (ASD) exhibit a high prevalence (55%) of gastrointestinal symptoms (GISs) and gut dysbiosis. Most studies involving children with ASD have focused on behavioral symptoms but not GISs. This systematic review and meta-analysis investigated the effects of gut microbiota-modulating interventions (GMMIs) on GISs and gut microbial composition in children with ASD. Five databases were searched for relevant domestic and international articles published from database inception until July 15, 2024. The meta-analysis included human trials wherein children with ASD received prebiotics, probiotics, synbiotics, or fecal microbiota transplantation. Intervention effects were measured on the basis of α-diversity, and genus- and phylum-level data were analyzed using a random-effects model and forest plots. This study included 19 trials (n = 1154). The results indicated that GMMIs significantly ameliorated GISs (p = 0.0017), reduced six-item Gastrointestinal Symptom Index scores by 1.86 points (p = 0.0187), and significantly increased the relative abundance of Bifidobacterium spp. (p = 0.0205). Longer interventions (≥ 8 weeks) were more effective in ameliorating GISs. Limitations in this investigation include the fact that the included studies neither incorporated any dietary control groups nor collected relevant dietary data, and the relatively small sample size (19 studies) may have hindered the identification of sources of heterogeneity in the pooled results. Overall, our findings suggest that GMMIs, especially probiotics, ameliorate GISs in children with ASD by modulating gut microbial composition, particularly by increasing the relative abundance of Bifidobacterium spp. These interventions may alleviate symptoms such as constipation, diarrhea, abnormal stool consistency and smell, flatulence, and abdominal pain. Our evidence supports that treatments involving GMMIs can be considered for children with ASD.
