Adjusting the populations of bacteria that live in the human gut might provide a powerful method for treating the symptoms of autism.
That’s the finding arising from an extensive meta-analysis of more than 150 papers written since the 1960s investigating links between gut contents and Autism Spectrum Disorder (ASD), published in Frontiers in Cellular Neuroscience.
The review, led by Qinrui Li of Peking University First Hospital in Beijing, China, notes that ASD symptoms are often accompanied by intestinal disorders, such as diahorrea and bloating, and sounds a hopeful, if cautious, note.
“Many recent clinical studies have shown that treatments that regulate the gut microbiota result in improvements in ASD symptoms,” the researchers write.
“However, well-designed research studies with more participants are needed to provide more evidence that supports the effectiveness of these treatments.”
The meta-analysis confirms a two-way linkage between gut health and the operation of the central nervous system, but also identifies differences in gut function that are found primarily in people with ASD.
“A fundamental factor underlying the relationships between ASD and the gut is the increased permeability of the intestinal tract of ASD individuals, referred to as a ‘leaky gut’,” the report states.
This condition means that substances – for instance, toxins produced by Lactobacillus bacteria – can more easily pass from the digestive system in the blood supply and then into the nervous system.
Some other species found in the gut biota excrete neuroactive compounds that in people with leaky guts can pass directly into the brain and cause abnormal behaviour patterns.
Li and his colleagues also found altering gut microbe colonies to be beneficial.
“Efforts to restore the gut microbiota to that of a healthy person has been shown to be really effective,” he says.
“Our review looked at taking probiotics, prebiotics, changing the diet – for example, to gluten-free and casein-free diets, and faecal matter transplants. All had a positive impact on symptoms.”
Currently almost 15 children per 1000 develop autism symptoms. The condition brings substantial emotional and financial hardships for parents, and can result in above-average use of healthcare and hospital services.
Current treatment measures centre on intensive rehabilitation and drug regimes, and are not consistently effective.
Therefore, the prospect of dramatically reducing the symptoms of autism through either controlling diet, or manipulating the gut microbiota through interventions such as faecal transplants, is extremely attractive.
Li cautions that large-scale studies are needed before the method can be rigoruously demonstrated. However, in the paper published in the journal Frontiers and Cellular Neuroscience, he and his colleagues conclude: