The link between intestinal health and the brain is a popular topic in science and the media currently. Approximately 95% of the neurotransmitter serotonin is made in the gut. (1) Ongoing research is interested in how this is related to a multitude of different psychological disorders including depression, anxiety, and autism symptoms. Rates of gastrointestinal upset in the autism community can be as high as 70%. (2) This includes constipation, nausea, diarrhea, fecal incontinence, and severe abdominal pain.
Opportunistic infections in the gut are a contributing factor for abdominal symptoms. Finegold, et al. found an overgrowth of many Clostridia yeast species in stool samples of autistic children compared to controls. Canadian researcher Derrick MacFabe et al. have shown in a rat model that propionic acid (PPA), a short chain fatty acid, is a neurotoxic byproduct of Clostridia fermentation. Administration of PPA to rats can cause brief, and reversible, autism-like behaviours. It is also elevated in the stool of autistic children. The above researchers maintain that the human microbiome influences behaviour, gene expression, and neurotransmitter function in individuals with autism.
Adams J, et al. determined that those on the spectrum have higher levels of bifidobacteria species in the gut and lower levels of lactobacilli. (3) Also they found that there is a strong correlation between autism severity and degrees of gastrointestinal problems. Caregivers who administered probiotics to their children were surveyed and the outcome was a 48% decrease in diarrhea severity, and 52% decrease in constipation severity. Decreases in ASD symptoms were reported by 88% of caregivers. (6) This was after 21 days of treatment with Lactobacillus rhamnosus species.
- Camilleri M. Serotonin in the Gastrointestinal Tract. Current opinion in endocrinology, diabetes, and obesity. 2009;16(1):53-59.
- Chaidez V, Hansen RL, Hertz-Picciotto I. Gastrointestinal problems in children with autism, developmental delays or typical development. Journal of autism and developmental disorders. 2014;44(5):1117-1127. doi:10.1007/s10803-013-1973-x.
- Adams JB, Johansen LJ, Powell LD, Quig D, Rubin RA. Gastrointestinal flora and gastrointestinal status in children with autism — comparisons to typical children and correlation with autism severity. BMC Gastroenterology. 2011;11:22. doi:10.1186/1471-230X-11-22.
- Finegold SM, Molitoris D, Song Y, Liu C, et al. Gastrointestinal microflora studies in late-onset autism. Clinical Infectious Diseases. 2002;35:S6– doi: 10.1086/341914.
- Thomas RH, Meeking MM, Mepham JR, et al. The enteric bacterial metabolite propionic acid alters brain and plasma phospholipid molecular species: further development of a rodent model of autism spectrum disorders. Journal of Neuroinflammation. 2012;9:153. doi:10.1186/1742-2094-9-153.
- West R, Roberts E, Sichel LS, Sichel J. Improvements in gastrointestinal symptoms among children with autism spectrum disorder receiving the Delpro® Probiotic and immunomodulator formulation. J Prob Health. 2013;1(102):2.