For example, in children with autism spectrum disorders (ASD), the expression of
intestinal disaccharidases is decreased so that the microbiota of the distal bowel receives a larger number of simple disaccharides like sucrose, lactose, and maltose (Williams et al., 2011). In addition, the increase in oxidizing conditions associated with the CDR in cells lining the intestine leads to changes in the uptake, intracellular processing, and folding of the proline and glutamine-rich, processed gliadin 33-mer peptide (Oguma et al., 2007), and to an increase in gluten sensitivity (Jacobs, 2007). These and other factors combine to alter the permeability and species composition in the gut. Among children with ASD, this commonly leads to dysbiosis and alternating bouts of constipation and diarrhea. It also leads to changes in behavior that are a result of communication abnormalities between the enteric nervous system (ENS) that monitors the health and function of the microbiome, and the central nervous system (CNS). Restoring a sick microbiome is not as simple as adding back missing or underrepresented species. Both the physical habitat of the gut and the nutrient resources delivered must be durably changed in order to produce a durable change in the complex microbial ecosystem.
