Written by Tatjana Djakovic, Staff Writer. In a study of 58 autistic children, an imbalance of beneficial bacteria was found and the researchers believe that digestive problems contribute to autistic behavior problems.
Autism is a developmental disorder that is associated with impairments in social interaction, communication and restricted repetitive patterns of interests and activities (1). Autistic behaviors include poor eye contact, difficulty in understanding and relaying social gestures, trouble in interpreting facial expressions and poorly developed empathy. There has been an increase in the prevalence of autism from 1 in 2500 in the 1980’s to 1 in 150 in the past decade (2).
Gastrointestinal problems are common in autism, as evidenced by a study of 137 autistic children, 25% had a history of at least one gastrointestinal symptom, particularly diarrhea (3). It has been hypothesized that gut inflammation makes the intestines more permeable, which may allow digestive products to enter the blood. Gastrointestinal problems in children may contribute to severity of the disorder due to abdominal pain, constipation, and diarrhea which cause frustration and decreased ability to concentrate on tasks, behavioral problems and aggression.
The current study was conducted in order to investigate the association between gastrointestinal problems in autistic versus healthy children. The study consisted of 58 autistic children aged 6.9 years and 39 healthy children aged 7.7 years. Prior to the start of the study, the autistic children had a higher incidence of gastrointestinal symptoms compared to healthy children (4).
In order to assess the severity of autism, the researchers used the Autism Treatment Evaluation Checklist (ATEC) that is composed of four subscales including: communication, sociability, sensory/cognitive awareness and health/physical behavior. Gastrointestinal symptoms were assessed using a modified version of Gastrointestinal Severity index that analyzed constipation, diarrhea, stool consistency, stool smell, flatulence and abdominal pain.
To investigate the impact of gastrointestinal disorder on the severity of autism groups, researchers divided the children into two groups, based on the amount of gastrointestinal problems. Interestingly, the severity of autism was 66% higher in the group that had the most gastrointestinal problems. In addition, all of the subscales were also higher in the group with the most gastrointestinal problems.
| Autism Low GI Problem Group | Autism-High–GI-Problem group | % difference | P value | |
| ATEC-total score | 49.0 | 81.5 | +66% | 0.00002 |
| ATEC Subscales Score | ||||
| Speech/Language/Communication | 6.7 | 13.7 | +103% | 0.0005 |
| Sociability | 11.5 | 17.6 | +53% | 0.002 |
| Sensory/Cognitive Awareness | 12.6 | 17.6 | +40% | 0.01 |
| Health/Physical Behavior | 18.7 | 32.6 | +74% | 0.00003 |
The strong correlation of gastrointestinal symptoms and severity of autistic symptoms suggests that gastrointestinal problems may significantly contribute to autistic symptoms in children. This evidence is further supported by a study that determined that antibiotics can temporarily reduce autistic symptoms, which suggests that autism and gut bacteria are related (5).
The researchers also studied the strains of beneficial bacteria in the gut of autistic and healthy children and determined that there was an imbalance of beneficial bacteria. Researchers reported high levels of Lactobacillus in the autism group and lower amounts of Bifidobacteria.
Possible markers of inflammation were investigated, including an enzyme, lysozyme, that is naturally capable of destroying cell walls of certain bacteria. The autism group had a 27% lower level of lysozyme compared to the healthy children (p=0.03). The beneficial bacteria were improved through the use of probiotics and fish oil supplementation. Probiotics did not have a significant effect on most of the bacteria, however, there was an increase of 30% in the level of “friendly bacteria,” Lactobacillus (p=0.08).
In addition, in the group of autistic children that consumed fish oil supplementation, there was 76.3% higher levels of Lactobacillus compared to the group that consumed seafood (p=0.0009).
The researchers also measured short-chain fatty acids which are molecules that are found in the colon and are produced as a result of bacterial fermentation, and in one study have been found to worsen the symptoms of autism. (6) The group of autistic children that took probiotics had a 44% lower level of short chain fatty acids than the control p=0.0000002, but no probiotic group also had 19% lower levels than the controls (p=0.006).
The authors suggest that the explanation for this occurrence is that there were lower amounts of beneficial bacteria to produce short chain fatty acids. Another possible suggestion is that there is higher absorption of short chain fatty acids through the bloodstream, which lead to lower levels in the stool (4). The link between autism and gut bacteria investigated in this study warrants further research as its implications are quite significant for the population.
Source: Adams, James B., et al. “Gastrointestinal flora and gastrointestinal status in children with autism–comparisons to typical children and correlation with autism severity.” BMC gastroenterology 11.1 (2011): 22.
© 2011 Adams et al; licensee BioMed Central Ltd. Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0)
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Posted July 22, 2013.
References:
- American Psychiatric Association. Diagnostic and statistical manual of mental disorders. 4th edition. Arlington (VA): American Psychiatric Association; 2000. p. 84.
- Steinhausen HC, Gobel D, Breinlinger M, et al. A community survey of infantile autism. J Am Acad Child Psychiatry 1986;25(2):186–9.
- Molloy Ca. et al., Prevalence of chronic gastrointestinal symptoms in children with autism and autistic spectrum disorders. Autism 2003, 7(2):165:171.
- Adams, James B., et al. “Gastrointestinal flora and gastrointestinal status in children with autism–comparisons to typical children and correlation with autism severity.” BMC gastroenterology 11.1 (2011): 22.
- Sandler RH. et al., Short-term benefit from oral vancomycin treatment of regressive-onset autism. Journal of Child Neurology 2000. 15(7):429-435.
- MacFabe DF. et al., Neurobiological effects of intraventricular propionic acid in rats: Possible role of short cahin fatty acids on the pathogenesis and characteristics of autism spectrum disorders. Behav Brain Res 2007, 176 (1): 149-169.
