Summary:
Autism spectrum disorder (ASD) involves social communication difficulties and repetitive behaviours, and many affected children also experience anxiety, gastrointestinal problems, immune differences and selective eating. The prevalence of ASD has increased, making early identification and investigation of contributing factors an important public health issue. A growing body of research has examined links between gut microbes, diet and neurodevelopment, however it remains unclear whether microbiome differences are a cause of ASD or a consequence of dietary habits commonly seen in this group. This study, a cross-sectional comparison, investigated whether diet or gut microbiome features are more strongly associated with ASD. Seventeen children with ASD were compared with non-ASD siblings and parents. Seven-day food diaries were collected, and gut bacterial and fungal composition was profiled. The gut microbiome did not differ meaningfully between groups, and microbial diversity was similar across all participants. In contrast, dietary patterns showed clear differences. Children with ASD consumed more sugary foods, fewer vegetables and had reduced dietary variety. Statistical analyses showed that diet, rather than microbiome composition, explained group differences. Overall, this study suggests that eating patterns typically seen in ASD may shape the gut microbiome, rather than microbiome changes driving behavioural characteristics. The findings highlight the importance of including dietary factors in microbiome research and suggest that nutritional approaches may be a useful area for further investigation in ASD.
Abstract:
Background/Objectives: Autism Spectrum Disorder (ASD) is a complex neurodevelopmental condition characterized by persistent social communication difficulties and restricted, repetitive behaviors, with prevalence estimates continuing to rise worldwide. The gut–brain axis has been proposed as a potential contributor to ASD, yet human studies yield inconsistent findings, partly due to confounding effects of diet and behavior. Methods: Here, we investigated the gut bacteriome and mycobiome of children with ASD (n = 17) compared with their non-ASD siblings (n = 9) and parents without ASD (n = 27), alongside detailed assessment of dietary intake (n = 79) using 7-day food diaries. Results: Multi-kingdom microbiome profiling revealed no significant differences in α- or β- diversity across ASD, sibling, and parental groups, with only minor taxonomic variation observed. Similarly, fungal community composition showed negligible group-level differences. By contrast, dietary patterns strongly differentiated ASD from non-ASD participants: children with ASD consumed higher levels of sweets and sugary foods, lower portions of vegetables, and exhibited reduced overall dietary diversity. Statistical analyses confirmed that dietary factors, rather than microbial composition, explained variation in ASD diagnosis. Conclusions: These findings suggest that selective and repetitive eating behaviors are characteristic of ASD shape dietary intake, which in turn influences gut microbial diversity. Thus, in humans, the directionality may run primarily from behavior to diet to microbiome, rather than from microbiome to behavior. Our results underscore the importance of incorporating dietary variables into microbiome research and highlight the need for targeted nutritional interventions to improve health outcomes in individuals with ASD.
Article Publication Date: 4/11/2025
DOI: 10.3390/nu17213476
