Diet, not gut bacteria, drives autism risk, Study suggests

Scientists have long debated whether gut microbiome differences could drive autism, but new evidence points to behavior and diet as key factors instead. In a recent study published in Nutrients, researchers found that children with autism spectrum disorder (AUTISM SPECTRUM DISORDER) exhibited strikingly different eating patterns from their non-AUTISM SPECTRUM DISORDER family members, yet their gut microbiome diversity was virtually identical. This finding suggests that, at least within families, selective eating in AUTISM SPECTRUM DISORDER may shape the microbiome more than the other way around.

Autism is a rising neurodevelopmental condition characterized by social and behavioral challenges, often accompanied by gastrointestinal issues and pronounced food selectivity. With past research hinting at links between microbiome composition and AUTISM SPECTRUM DISORDER symptoms, this study set out to disentangle the complex relationship between microbial communities, diet, and behavior in affected children versus their siblings and parents.

Researchers recruited 17 AUTISM SPECTRUM DISORDER children, 9 non-AUTISM SPECTRUM DISORDER siblings, and 27 parents from Italian families, extending dietary analysis to 79 individuals in total. Fecal samples were collected and analyzed using advanced DNA sequencing to assess both bacterial and fungal components of the microbiota. Seven-day food diaries and food-frequency questionnaires provided a detailed snapshot of dietary intake, categorized into eight food groups. Microbial diversity and community structure were evaluated using robust statistical approaches, with dietary and microbiome data integrated using linear mixed-effects models that controlled for shared genetics and environment within families.

Gut microbiome analysis showed no significant differences in bacterial or fungal diversity between children with AUTISM SPECTRUM DISORDER and their family members, contradicting some previous reports of microbiome “dysbiosis” in autism. However, dietary profiles differed markedly: AUTISM SPECTRUM DISORDER children ate more sugary foods and fewer vegetables than both siblings and parents, and these group-level dietary distinctions were statistically significant. Smaller differences in fruit and processed food intake mainly distinguished children from adults, rather than AUTISM SPECTRUM DISORDER from non-AUTISM SPECTRUM DISORDER.

The study’s strengths include its within-family design, which controls for genetics and environment, and its integration of both microbiome and dietary data. However, the small sample size and cross-sectional nature limit the ability to draw causal conclusions. Notably, some associations faded on more complex modeling, highlighting the need for larger studies.

Lead author Dr. Valentina Pontrelli notes that these results support a model in which dietary habits, influenced by AUTISM SPECTRUM DISORDER behaviors, may be the primary drivers of microbiome differences within families. Larger, multi-omic studies will be necessary to clarify whether subtle microbiome effects emerge when genetic and dietary variables are rigorously controlled, and to optimize dietary interventions for children with AUTISM SPECTRUM DISORDER.

REFERENCE: Di Benedetto, G., Sorge, G., Sarchiapone, M., & Di Martino, L. (2025). Dietary Patterns, Not Gut Microbiome Composition, Are Associated with Behavioral Challenges in Children with Autism: An Observational Study. Nutrients 17(21): 3476. DOI: 10.3390/nu17213476, https://www.mdpi.com/2072-6643/17/21/3476