Safety and efficacy of a novel fecal microbiota transplantation method using hydrogen nanobubble water without antibiotics or bowel cleansing in children with autism spectrum disorder: an open-label, single-arm study demonstrating improvements in core and comorbidity symptoms.

Background: Autism spectrum disorder (ASD) is rising in prevalence, but effective treatments for its core symptoms remain limited. Fecal microbiota transplantation (FMT) has shown promise; however, conventional methods often require antibiotics and bowel cleansing, raising concerns regarding safety and sustainability. We developed a novel FMT method using hydrogen nanobubble water and investigated its efficacy and safety. Methods: This prospective, single-arm, before-and-after comparative study enrolled 30 children aged 5-12 years with ASD, selected according to inclusion and exclusion criteria. SHIN-1, a Good Manufacturing Practice (GMP)-grade prepared fecal microbial solution from a healthy screened donor, was suspended in hydrogen nanobubble water and administered via enema. Primary outcome was the Social Responsiveness Scale-2 (SRS-2), with objectivity confirmed using Gazefinder as an eye-tracking system. Secondary outcomes included sensory profile [Short Sensory Profile (SSP)], gastrointestinal symptoms [Gastrointestinal Symptom Rating Scale [GSRS], Bristol Stool Form Scale [BSFS]] and Patient Health Questionnaire-4 items (PHQ-4). Statistical analyses employed paired t-tests or Wilcoxon signed-rank tests ( Results: At 30 weeks, fecal microbiota reconstitution was observed, with increases in short-chain fatty acid-producing and typically taxa abundant in developing children. SRS-2 scores decreased 29% ( Conclusion: This novel hydrogen nanobubble water-based FMT method was safe and effective, reducing both core and peripheral symptoms of ASD and suggesting broad benefits via the gut microbiota-brain axis.