Children diagnosed with autism spectrum disorder (ASD) are at an increased risk of experiencing gastrointestinal (GI) discomfort, which has been linked to dysfunctions in the microbiome–gut–brain axis. The bidirectional communication between gut and brain plays a crucial role in the overall health of individuals, and alterations in the gut microbiome can contribute to immune activation and gut–brain dysfunction in ASD. Despite the limited and controversial results of pre-/probiotic applications in ASD, this review comprehensively maps the association between ASD clinical symptoms and specific bacterial taxa and evaluates the efficacy of pre-/probiotics in modulating microbiota composition, reducing inflammatory biomarkers, alleviating difficulties in GI distress, sleep problems, core and other ASD-associated symptoms, as well as relieving parental concerns, separately, in individuals with ASD. Beyond simply targeting core ASD symptoms, this review highlights the potential of pre-/probiotic supplementations as a strategy to modulate gut homeostasis and immune response, and to delineate the potential mechanisms by which its direct or mediating effects can alleviate gut–brain dysfunction and poor nutritional status in ASD management. Further well-designed randomized controlled trials are needed to strengthen the existing evidence and establish optimal protocols for the use of pre-/probiotics in the context of ASD.

Autism spectrum disorder (ASD) frequently co-occurs with malnutrition and gut dysbiosis, yet the underlying mechanisms remain poorly understood. Herein, this cross-sectional study first profiles dietary intake differences using dietary records from 210,874 participants (ASD = 232; non-ASD = 210,642; median age = 56.18) from the UK Biobank (UKB). Second, a bi-directional Mendelian Randomization (MR) approach serves to dissect relationships between ASD genetic susceptibility and dietary preferences by leveraging genome-wide association metadata from the iPSYCH-PGC (ASD) and UKB (dietary intake/food-liking traits). The same strategy is implemented to identify ASD-associated gut microbial species. Mediation analyses further assess the role of gut microbiota in the association between ASD and dietary preferences. Subjects with ASD exhibit higher consumption of cheese, processed meat, and oily fish, alongside lower intake of fruits, and demonstrate a preference for high-fat/salt and energy-dense foods. Additionally, the depletion of Turicibacter, Streptococcus, and Lachnospiraceae NK4A136 was causally related with ASD (all false discovery rate < 0.05; β = −0.15, β = −0.10, β = −0.093, respectively), which significantly mediates the ASD-associated elevated preference for high-fat/salt foods. In conclusion, ASD is associated with specific dietary preferences, likely mediated via gut microbiota, highlighting the future potential of gut microbiome-based therapeutics to modify eating disorders for ASD.