Autism – the Digestion Connection

Behaviour and health are intimately linked. Everyone is aware of how physical ill health affects mood and energy levels and how a chronic physical condition can affect personality and outlook.

The same is true for children. Not only are children beginning to experience health problems never seen before in childhood such as ulcerative colitis and obesity, but many children are starting life suffering from varying degrees of learning and behavioural issues.

One such issue is autistic spectrum disorder (ASD). When Leo Kanner published his original paper on the subject of autism in l943, it was considered to be a rare condition (1). At that time, incidence of autism was 2-4 per 10,000 children. Fifty years later this had risen to 60 per 10,000 (2). Some of this rise may be accounted for due to improved diagnosis.

What is Autism?

Autism is now known to be a spectrum of conditions ranging from Asperger’s Syndrome on the one hand, to Classical autism as described by Kanner in 1943.  It is a complex developmental disorder which can be noticeable when the child is a few months old, though is more commonly identified at 3-4 years old when different behaviour is more apparent and easier to observe. It is identified by impairments in the three areas of communication, socialisation and imagination:

  • rigidity of behaviour
  • impaired communication
  • obsessive-compulsive disorder, developmental dyspraxia, or other developmental or psychiatric conditions

According to epidemiologist Jim Gurney, ‘one person’s autism is not another person’s autism’, and diagnosis is a subjective process of observing behaviour, as there is no definitive biochemical or genetic testing available.

To understand the complexities and idiosyncratic nature of the autistic spectrum, you may wish to read ‘Autism: Explaining the Enigma‘ by Ute Frith.

Controversy arose over the issue of the MMR vaccine initiating gastrointestinal inflammation in ASD sufferers, and there certainly appears to be a crucial link between digestive disturbance and autistic symptoms. However, Japanese research concluded in 2005 that the vaccine is ‘most unlikely to be a main cause of ASD’ as the incidence of ASD rose significantly even in unvaccinated children (3).

The Importance of Digestion

A common contributing factor to the spectrum of autistic disorders is often the failure to establish healthy gut flora in early life. Many children suffer from dysbiosis due to antibiotics given at a young age and may have developed imbalanced colonies of gut bacteria due to caesarian delivery and/or formula feeding. Long term dysbiosis can cause inflammation in the gut lining and increased gut permeability.

Clinical trials have shown that gastrointestinal symptoms including inflammation and dysfunction are commonly present in autistic children. Mild to moderate inflammation was found in both upper and lower intestinal tract, as well as decreased liver sulfation, and intestinal permeability, in many children suffering from ASD (4).

Infection with Clostridium was found in some children, mainly species not found in controls, and the Cetobacterium somerae was present in the stool in some cases. Significant dysbiosis is also a widespread problem (5,6).

Other digestive problems extremely common in ADHD (Attention Deficit Hyperactivity disorder, which is closely related to ASD) are constipation and diarrhoea (7)

Food Intolerance

It has been suggested that peptides from gluten and casein may have a role in the origins of autism and that the physiology and psychology of autism might be explained by excessive opioid activity linked to these peptides. Research has reported abnormal levels of peptides in the urine and cerebrospinal fluid of persons with autism. If this is the case, diets free of gluten and /or casein should reduce the symptoms associated with autism. The authors of the Cochrane Report concluded that this is an important area of investigation and large scale, good quality randomised controlled trials are needed (8).

The Role of Probiotics

Lactobacillus acidophilus is the most widely studied of all probiotics and is known to stimulate immunity increasing levels of interleukin-1 alpha and TNF-alpha, and also promote non-specific immunity and protect against infective diarrhoea and inflammatory bowel disease (9).

Bifidobacteria have been shown to enhance gut immunity and reduce the incidence of gut infections in children by preventing the build up of intestinal endotoxin and preventing adherence of E coli. B. Bifidum can also protect the gut lining from lipid peroxidation due to notable antioxidant capacity (10).

Glutamine’s Role

Glutamine is essential for maintenance of a healthy gut lining. It’s also used as fuel by the intestinal cells for repair of the lining. Glutamine has been shown to modulate inflammation and reduce frequency of infection. In autistic children, plasma glutamine levels are often reduced and amino acid metabolism dysfunctional. Children with autism have also been found to have low levels of the glutamine dependent enzyme glutathione, which could give rise to free radical accumulation and damage to the brain (which is a feature of many other neurodegenerative conditions such as Alzheimer’s and Parkinsons).


Whilst nutritional factors may not be a direct cause of autism, they may play a role in increasing symptoms. The role of the practitioner is to investigate possible contributory factors, such as food intolerances, but dysbiosis or nutritional deficiencies, which may be contributing to mood behaviour or learning. In addition to the digestive and immune  support as outlined above which nutrition-orientated practitioners may offer, further progress may be made by using a spectrum of multi-nutrients and essential fatty acids especially omega 3.


1. Kanner L. Autistic disturbances of affective contact. Nervous Child 2, 217-250 (1943)

2. Wing and Potter. The Epidemiology of Autistic Spectrum Disorders: Is the prevalence rising? Mental Retard Dev Disabil Res Rev 2002;8(3):151-61

3. Honda H, Shimzu Y, Rutter M. No Effect of MMR Withdrawal on the Incidence of Autism: a Total Population Study. J. Cild Psychol Psychiatry 2005 Jun; 46 (6) 572-9

4. Horvarth et al. Autism and gastrointestinal symptoms. Curr Gastroenterol Rep 2002 Jun;4(3):251-8

5. Finegold et al. Gastrointestinal microflora studies in late-onset autism. Clin Infect Dis 2002 Sept 1;35 (Suppl 1): S6-S16

6. Erickson et al. Gastrointestinal Factors in Autistic Disorder: A Critical Review. J Autism Dev Disord 2005 Nov 3; 1-15

7. Martirosian G. Anaerobic Intestinal microflora in pathogenesis of autism. Peopstepy Hig Med Dosw 2004 Sep 20: 58:349-51

8. Illward C, et al. Gluten and casein-free diets for autistic spectrum disorder. Cochrane Database of Systematic Reviews 2008, Issue no. 2

9. Gionchetti P, Rizzello F, Venturi A, Campieri M.J.  Probiotics in infective diarrhoea and inflammatory bowel diseases. Gastroenterol Hepatol. 2000 May;15(5):489-93.

10. Griffiths EA, Duffy LC, Schanbacher FL, Qiao H, Dryja D, Leavens A, Rossman J, Rich G, Dirienzo D, Ogra PL. In vivo effects of bifidobacteria and lactoferrin on gut endotoxin concentration and mucosal immunity in Balb/c mice. Dig Dis Sci. 2004 Apr;49(4):579-89.