The most common medical condition associated with autism is gastrointestinal disorder. (Nikolov 2009)

MIND institute (University of California, Davis) documented that children with autism were eight times more likely to suffer from one or more chronic GI problems than other children. (Chaidez 2014)  Common GI issues include diarrhoea, constipation, painful stooling along with gaseousness and abdominal pain.  The study also linked chronic GI issues with increased severity of autism behavioural symptoms, including irritability, hyperactivity, social withdrawal and repetitive behaviours.  It also found a strong association between GI issues and autism symptoms among nonverbal persons who have difficulty in communicating pain and distress.

The microbiome

There is evidence since the late 1990s, that any unhealthy change in the intestinal tract’s normal community of digestive bacteria (microbiome) drive both behavioural and GI problems in some people with autism.  Ellen Bolte was the first person to notice the gut-brain connection. The mother of a child with autism saw a parallel between her son’s symptoms and infant botulism. (Bolte 1998) Ms. Bolte’s ideas inspired many researchers.  Sydney Finegold, an infectious disease specialist at University of California, Los Angeles showed that bacteria in the intestine produce toxins that spike and affect the brain via the vagus nerve between the digestive tract and the brain. (Finegold 2002)

Identification and treatment

The first guidelines, published in the year 2010 in the journal Pediatrics, helped healthcare providers to identify and treat GI problems in children with autism. (Buie 2012)  These guidelines emphasized that a detailed evaluation for GI distress is particularly important in those children who have an unexplained spike in behavioural problems.  The specific issues included:

  1. Chronic constipation

A survey conducted in the year between 2006 and 2010, by U S Center for Disease Control (CDC) found that children with autism were more 3.5 times more likely to suffer chronic constipation or diarrhoea than were typically developing children. (Schieve 2012) Difficulty in emptying the bowels refers to constipation which involves hard stools.  Periodic constipation is normal, but chronic constipation (lasting two weeks or more) can lead to several medical complications which include haemorrhoids, rectal fissures and prolapse of the rectum and or lower intestines.  Apart from the associated pain, passing hard stools can lead to an aversion to toileting that contributes to the problem.

It’s more challenging to recognize GI distress among many who have autism particularly the non-verbal and minimally verbal, and those with intellectual disability in communicating the pain and distress.  Tell-tale behaviour can include arching the back, pressing the belly and gritting teeth. GI pain can also prompt spikes in self-soothing repetitive behaviour as well as irritability, aggression, self-injury and other challenging behavioural issues.

Factors that contribute to chronic constipation:

  • Insufficient fiber in the diet, particularly common with gluten-free diets as well as highly restricted diets associated with sensory aversion (Miranda 2014, Graf-Myles 2013)
  • Certain behavioural medication including risperidone (De Hert 2011)
  • Behavioural issues and /or sensory issues that interfere with regular toileting (Dalrymple 1992)

Anatomic, neurological or metabolic problems and abnormal gut motility (a sluggish intestinal tract) are less common but potentially more serious contributors.

Medical and behavioural intervention are the best combination in the treatment plan.  Behavioural management includes dietary changes such as increasing the amount of fiber in the diet and to restrict or eliminate the foods that causes constipation and which helps in managing toileting behaviours, also includes making the child learn to sit on the toilet after meals.  Medication may include laxatives and / or soluble fiber.

  1. Chronic diarrhoea

Periodic bouts of diarrhoea are normal, but chronic (two weeks or more) can adversely affect the health and quality of life.  It is important to evaluate and address medical causes such as immune dysfunction, inflammatory bowel diseases (Crohns or ulcerative colitis), intestinal function, irritable bowel syndrome, celiac disease (gluten intolerance), certain food allergies, lactose intolerance or excessive consumption of certain foods or drinks

Diarrhoea in people with autism often results from severe constipation.  This happens when hard, stuck stools cause a backup of watery contents.   The watery contents spill around the hard stools to cause the sudden diarrhoea.

Evaluation, investigation is recommended to initiate the treatment depending on the cause.  Dietary changes can ease diarrhoea which may be due to excessive juice, food allergies, lactose intolerance or celiac disease.

  1. Gastroesophageal reflux disease (GERD)

The muscle between the stomach and oesophagus (food pipe) when relaxed results in gastroesophageal reflux disease (GERD).  In this condition the partially digested food and liquid mixed with stomach acid to move up out of the stomach.  GERD may cause ulceration of the oesophagus and predispose a person to oesophageal cancer.  The evaluation of the medical condition and an expert referral is recommended.

Experts/ healthcare professionals often look for symptoms such as throat discomfort and/ or feelings of heartburn, children sometimes experience GERD pain in atypical ways. The most challenging is when nonverbal or minimally verbal people have difficulty in expressing or communicating their pain and discomfort. Few signs of GERD pain include an increase in repetitive and self-injurious behaviour which may include head banging, as well as other challenging behaviour.  Tell-tale behaviour can include unusual body postures, straining the neck, pushing out the jaw or tapping the throat.  These behaviours are triggered when the person lies down, which helps professionals to identify, with additional signs or symptoms including hoarseness, chronic sore throat, cough or heartburn, dental erosions, food refusal or disturbed sleep.

One of the most important changes required is to avoid foods that tend to trigger symptoms, eating smaller meals and avoiding food near bedtime. Severe and chronic GERD warrants tests to identify acid levels and tissue damage in the oesophagus.

Casein- and gluten-free diets

Gluten is primarily found in wheat, barley rye; casein is found in milk products.  Studies have shown that a diet free of the protein gluten and casein had an improvement on behaviour of the children with autism. (Pillsbury 2016)

Studies found little evidence that casein and gluten-free diets reduce autism symptoms. (Mulloy 2010). Researchers from the university of Rochester Medical center conducted a clinical trial on children with autism, that switched to a diet that included gluten and casein, and a diet free of them. They used look alike, taste alike foods. (Hyman 2016) Neither the children, their parents nor the researchers knew who was getting which food until after two segments of the study were completed.  There was not much significant behavioural change in children with autism after the analysis of their daily diaries.  However, researchers say that it is possible that a small subset of people with autism do benefit from a gluten- and casein-free diet.


Fermented /cultured foods such as yogurt, idli, dosa, cheese, etc., contain probiotic bacteria so called “good” or healthy bacteria.  There are a few promising results with fermented foods, in studies with mice bred to display autism- like symptoms such as social avoidance and repetitive behaviours. (Hsiao 2013, Critchfiled 2011, Breece 2013)  Researchers at Ohio State University are enrolling children with autism in a clinical trial to evaluate whether a well-studied probiotic (a “good,” or health-promoting bacterium) can relieve anxiety and improve quality of life in children who have autism.



Sri Lakshmi H A  (Senior Nutritionist)