Autism spectrum disorder

Autism is described as a lifelong condition affecting social, cognitive and imaginative abilities (1). There is a great deal of controversy over the choice of treatment, with complementary and alternative treatments often being self-prescribed. Gluten-free and casein-free diets are one such treatment.

Treatment with gluten-free and casein-free diets centres on the opioid-excess theory of autism; the principle of which is that autism is the result of a metabolic disorder. Foods that contain gluten and casein are high in peptides with opioid activity. These peptides are able to pass through the intestinal membrane which is thought to be abnormally permeable (2) and enter the central nervous system. This has an effect on neurotransmission and can produce other physiological symptoms associated with autism. Abnormal levels of urinary peptides have also been reported in people with autism (3). This had lead to the theory that removal of casein and gluten from the diet should reduce the symptoms associated with autism.

The majority of research in this area is anecdotal, and studies have been done on a very small scale (4). There is therefore very little evidence to support using such a restrictive diet in the treatment of people with autism.

One area that needs careful consideration before implementing a gluten-free casein-free diet is the impact that the diet will have on food choice and nutrition. Children with autism often have selective eating and therefore self-limiting diets. One small research project found that nearly 90% of autistic children studied followed repetitive patterns of food choice (5). Research has looked at the nutritional intake of children with autism and considered how this can be affected by restrictive diets such as gluten-free casein-free (5,6). The study by Cornish (2002)(5) did not find any statistical difference between the dietary intakes of children on exclusion diets and those on a normal diet. Arnold et al (2003)(6) found that children with autism spectrum disorder had more essential amino acid deficiencies (consistent with poor protein nutrition) than a group of control children and the children on restricted diets had an increased level of deficiency compared to children with ASD on a normal diet. Both these studies were very small scale, and the inconsistency in the findings suggests that larger scale studies are required.

Should gluten-free casein-free diets be recommended for children with ASD?

For many children with autism the foods they will accept are gluten/casein containing foods; so this must be considered before such a restrictive diet is commenced.

As there is a great deal of anecdotal evidence to support the use of the gluten-free casein-free diet for ASD, it may help certain individuals, so the use of this diet needs to be considered on an individual basis. Suggested good practice guidelines form the British Dietetic Association (7) suggests:

• Informing the parent about the lack of evidence, the potential harm and benefits.
• Considering the current dietary intake needs and the impact of a restricted diet.
• Supporting the person still wishing to try the diet. A dietitian should advise on and check the nutritional adequacy of the diet.
• An MDT approach is strongly recommended.
  It is wise to refer the patient to an experienced paediatric dietitian before the diet is commenced. 

References

1 American Psychiatric Association 1994

2 Furlano RI et al. Colonic CD8 and T-cell Infiltration with Epithelial Damage in Children with Autism. The Journal of Paediatrics 2001;138(3):366-372.

3 Shattock P et al. Role of Neuropeptides in Autism and their relationships with classical Neurotramsmitters. Brain Dysfunction 1990;3:328-345.

4 Knivsberg AM et al.  A randomised, controlled study of dietary intervention in autistic syndromes. Nutritional Neuroscience 2002;5(4):251-61

5 Cornish E. Gluten and casein free diets in autism: a study of the effects on food choice and nutrition. Journal of Human Nutrition & Dietetics 2002;15(4):261-9

6 Arnold GL et al. Plasma amino acids profiles in children with autism: potential risk of nutritional deficiencies. Journal of Autism & Developmental Disorders 2003;33(4):449-54

7 Isherwood E, Thomas K. Professional Consensus Statement. Dietary Management of Autism Spectrum Disorder. Dietitians working in Autism Spectrum Disorder supported by The British Dietetic Association Specialist Mental Health group. September 2002