The Gut-Brain Connection: Why Healing the Microbiome Can Transform Neurodevelopmental Health
In 2010, Laura de Magistris and colleagues published a study in the Journal of Pediatric Gastroenterology and Nutrition that compared intestinal permeability in children with autism, their first-degree relatives, and healthy controls. They found significantly elevated intestinal permeability in 36.7 percent of children with autism, compared to 4.8 percent of controls. This is the phenomenon often called “leaky gut”: tight junctions between intestinal epithelial cells become loose, allowing larger molecules (partially digested food proteins, bacterial endotoxins, microbial fragments) to pass through into the bloodstream where they trigger immune responses. When this happens, several cascades unfold. Lipopolysaccharide (LPS), an endotoxin shed by gram-negative bacteria, enters circulation and triggers systemic inflammatory cytokines that can cross the blood-brain barrier and activate microglia, the brain’s resident immune cells. Food peptides that should have been digested into amino acids reach the bloodstream and provoke immune memory and food sensitivities. Mast cells, distributed throughout the gut, lung, and brain, become primed and start releasing histamine, tryptase, and inflammatory mediators in response to ordinary stimuli. The gut-immune-brain axis is one continuous loop, and dysfunction at any node propagates throughout the system. Digestive Enzyme Insufficiency A separate but related problem has emerged from endoscopic biopsy studies in children with autism: many of them simply cannot digest sugars and carbohydrates properly. In 1999, Karoly Horvath and colleagues evaluated 90 children with autism undergoing endoscopy and found that 49 percent had at least one deficient disaccharidase enzyme (lactase, maltase, sucrase, palatinase, or glucoamylase), and 20 percent had deficiencies in two or more. Lactase deficiency was the most common. A 2011 study by Williams and colleagues, published in PLoS ONE, confirmed and extended these findings, also documenting altered intestinal microbiota associated with the carbohydrate digestion impairment.