Autism and the Gut—A Need for Digestive Enzymes

Autism is a developmental disorder characterized by severe abnormalities in communication, social awareness and skills, and behavior. Before the 1980s, autism occurred in 2 to 5 of every 10,000 children. Today about 1 in every 110 children gets autism. This rapid increase cannot only be attributed to improved diagnosis, and also indicates there is more to the disorder than simply genetics. Indeed, autism is a combination of genetic predisposition with environmental factors that triggers its development.

One aspect of contributing factors, at least in a subset of children, involves gut dysfunction. Many reports describe gastrointestinal symptoms and abnormalities in up to 84% of children with autism. From constipation, diarrhea, abdominal discomfort, food sensitivities and abnormal gut flora to immune dysfunction and gut and systemic inflammation, the digestive system plays a central role in many cases of autism.

One gut abnormality—lactose intolerance—found in people with autism was recently reported in the journal Autism. Intestinal disaccharidase activity was measured in 199 individuals with autism. Disaccharidase is an enzyme that breaks larger sugars (disaccharides) like lactose, maltose and sucrose into smaller sugars like glucose. Deficiency of lactase enzyme, the enzyme that breaks milk sugar, or lactose, into galactose and fructose, was found in 58 percent of autistic children and 65 percent of autistic adults. In children, boys under 5-years-old had 1.7-fold lower lactase activity than girls of the same age, indicating the problem may be more severe in boys. The study concluded that lactase deficiency is common in autistic children and may contribute to abdominal discomfort, pain and the observed abnormal behavior seen in autism. Further, the study points out that most autistic children with lactose intolerance are not identified when doctors take a clinical history.

A decrease in activity of a variety of carbohydrate-digesting enzymes has been reported in children with autism.   Carbohydrase and disaccharidase enzyme deficiency results in the incomplete breakdown of carbohydrates in the small intestine. These partially undigested carbs move into the colon where they are greeted by a large supply of “hungry” bacteria—including potentially pathogenic bacteria. This may explain the increased presence of Candida and Clostridia species found in the guts of autistics.

Carbohydrate-digesting enzymes are not the only digestive enzymes that may cause problems in autism. Fat malabsorption is seen in some autistic children, resulting in fatty, loose, floating, foul-smelling stools, also known as steatorrhea. Further, a particular enzyme known as dipeptidyl peptidase-4 (DPP4) may be deficient in those with autism. This enzyme breaks a specific peptide bond in gluten and casein proteins. In fact, it is thought that a deficiency in this enzyme is responsible for the incomplete breakdown of casein and gluten peptides (known as gluteomorphins and casomorphins) that act as opioids in the central nervous system and are thought to contribute to autistic symptoms. Following a gluten-free and casein-free diet has been found helpful in many autistics because it eliminates exposure to these peptides, often relieving symptoms. Supplemental DPP4 can be given in cases where accidental ingestion of gluten- or casein-containing foods is suspected, but it is not recommended as a replacement for the gluten-free, casein-free diet.

In all, we see a variety of enzyme deficiencies in autism and it would be wise to supplement with a digestive enzyme formula that includes a variety of enzymes. Further, due to the many digestive abnormalities seen in autism, the HOPE Formula (High-fiber, Omega oils, Probiotics and digestive Enzymes) is a wise daily maintenance program to support gut health.


[1] Gilger MA and Redel CA, “Autism and the gut.” Pediatrics. 2009 Aug;124(2):796-8.

[2] Horvath K, et al., “Gastrointestinal abnormalities in children with autistic disorder.” J Pediatr 1999;135:559-63.

[3] Finegold SM, et al., “Gastrointestinal microflora studies in late-onset autism.” Clin Infect Dis. 2002 Sep 1;35(Suppl 1):S6-S16.

[4] Shaw W, et al., “Assessment of antifungal drug therapy in autism by measurement of suspected microbial metabolites in urine with gas chromatography—mass spectrometry. The Clinical Practice of Alternative Medicine Magazine. 2000;1:15-26.

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