Research published recently from two separate studies suggests not only that gut symptoms are common in children with autism but that the severity of these gut issues is directly linked to the severity of the the behavioural aspects associated with the disorder.
In one of the studies scientists compared the gut flora of children with autism to that of neurotypical children and also looked at the relationship between severity of gastrointestinal symptoms in autistic children and their overall condition. In a second study, researchers sought to find out how common deficiencies in the enzymes that digest simple sugars, such as lactose, are among autistic children.
Many parents report that their autistic children seem to suffer more digestive upset than their peers and an increasing amount of research suggests that gut problems are indeed a common component of austim spectrum disorders (ASDs). In fact a specific form of enteropathy (disease of the intestinal tract) involving an abnormal immune response and inflammation has been identified in children with autism. These two latest studies may help to shed more light on the reasons for this.
The first study was led by researchers at Arizona State University and the results are published in the journal BMC Gastroenterology. The team assessed gut flora composition and markers of digestive health in 58 children with ASDS and 39 neurotypical children using diagnostic techniques developed by Doctors Data, a commercial lab serving physicians who practice functional or integrative medicine. Gastrointestinal symptoms of all the children were also assessed, as were the severity of autistic symptoms in those with ASDs, using a standard questionnaire (GI Severity Index) and checklist (ATEC), respectively.
The researchers report a strong associated between severity of gastrointestinal symptoms and severity of autistic symptoms. Significant findings from the stool analysis included the observation that children with autism had lower numbers of Bifidobacteria and lower levels of Lactobacillus species along with much lower levels of short-chain fatty acids (SCFAs) (e.g. acetate, proprionate, valerate) than their healthy counterparts. Whether these differences cause or exacerbate the gastrointestinal symptoms seen in the autistic children is unclear but Bifidobacteria and the SCFAs they produce are known to play an important role in the health of the gut - and as is increasingly apparent from other research - health well beyond the gut, including that of the brain.
The second study was carried out at Harvard Medical School and the results are published in the journal Autism. The study involved 199 children with autism who were all assessed for levels of the sugar-digesting enzymes lactase, sucrose, and maltase present in the tissues of their duodenum (upper part of the small intestine). Deficiency of these enzymes leads to incomplete digestion of the sugars lactose, sucrose, and maltose, which in turn frequently results in symptoms including bloating, flatulence, and diarrhoea.
The Harvard researchers found that lactase deficiency was present in 58% of the children in the study aged under 5 years and in 65% of children over 5 years. These figures are considered to be much higher than the average for children across a mixture of ethnic backgrounds. No significant findings relating to sucrase or maltase were noted.
The high incidence of lactase deficiency among autistic children is important since as the form of sugar present in milk and dairy products, lactase is often present in high amounts in a child's diet. The researchers conclude that lactase deficiency is not associated with intestinal inflammation or injury but may contribute to the adbdominal discomfort, pain, and behavioural traits seen in autistic children.
Adams JB Johansen LJ Powell LD Quiq D Rubin RA (2011) Gastrointestinal flora and gastrointestinal status in children with autism -- comparisons to neurotypical children and correlation with autism severity BMC Gastroenterology 11(1):22
Kushak RI Lauwers GY Winter HS Buie TM (2011) Intestinal disaccharidase activity in patients with autism: Effect of age, gender, and intestinal inflammation Autism [Epub ahead of print]