The Role of the Gastrointestinal Tract
The microbiota–gut-brain axis is the biochemical signaling that takes place between the GI tract and the CNS, meaning that there is an association between the processes in the microbiota, gut, and brain and that they provoke alterations in each other.
About 70% of all children with ASD have GI problems, which is 6 to 8 times more frequently than healthy children. It has been shown that some specific symptoms of ASD, such as anxiety and sensory sensitivity correlate with these GI problems.
Gut-brain relationship can be circular: oxidative stress from inflammation shifts the balance of colonic bacteria composition, and at the same time pathogenic gut bacteria causes oxidative stress. Additionally, gene alterations were shown to be the result of inflammation caused by infection may negatively affect the gastrointestinal repair processes.
Viral infections causing inflammation, brain and genes alterations also might induce intestinal neuromuscular dysfunction, which suggests the role of viral infection in gut-brain damage.
Moreover, there is an connection between the gut-brain axis and the immune system. The gut-brain axis regulates such functions of the immune system as the proliferation of regulatory T-cells, neutrophil activation and migration of the monocytes and macrophages and is mainly responsible for the immune system functioning. The disrupted immune system, in turn, loses the ability to control existing infections.
So, we see that the gastrointestinal tract plays an important role in autism, but not as the initial cause, but rather as a side effect of the existing factors such as infections and inflammation.
That is why diets, colon cleanses and probiotics alone will not help to solve the problems, but will in some cases help with such problems as anxiety and hyperactivity.