Overview
Fecal microbiota transplant (FMT) for ASD aims to replace the dysbiotic gut community with a diverse donor microbiome. Open-label results show improvements in both GI symptoms and behavioral measures, but benefits are lost within weeks after cessation.
Mechanism
- Introduces missing beneficial taxa (Bifidobacterium, Prevotella) that are consistently depleted in ASD
- Restores SCFA production and tryptophan metabolism via gut-brain axis
- Displaces Clostridium species associated with propionic acid overproduction
Clinical Evidence
Open-label study (n=40):
- GI symptoms decreased by 35%
- ABC scores improved across multiple subscales
- Microbiota composition shifted measurably toward typically developing (TD) profiles
- Critical limitation: Benefits were lost within weeks after FMT cessation, suggesting ongoing maintenance may be required
Clinical Considerations
- Not yet FDA-approved for ASD; available only in research settings
- Donor screening and preparation protocols vary significantly across studies
- The transient nature of benefits suggests the underlying ecological pressures (diet, metal burden, immune state) must also be addressed
- May be most effective when combined with dietary and environmental interventions that sustain the transplanted community