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Diet and autism: fresh evidence

Posted May 20 2010 12:00am

Gluten free and Casein free (GF/CF) diets have been suggested for autism for many years. A survey of parent members of the National Autistic Society in 2005 found that even though only 7.5% cited gastro-intestinal (GI) difficulties as an issue for their child around half had used special diets of one sort or another. Between 10 and 20 percent reported improvements following the diet and around 10 percent wanted more research into diets and other biomedical interventions. Although most of the GI issues were reported in children with autistic disorder parents of children with Aspergers Syndrome supported the use of special diets in comparable numbers. In line with Paul Shattock’s oft quoted remark that nobody ever died of a gluten deficiency parents have often regard the GF/CF diet as essentially benign. It may be expensive and time consuming to implement but it cannot do any harm and may help with behaviour. So where is the harm in trying it?

The most obvious source of harm is the nutritional effect of limiting the type of foods offered to a growing child. Foods that contain gluten and casein also contain essential nutrients that may not be present in the GF/CF alternatives. Two years ago the National Institutes of Health reported on problems with bone density in autistic boys

The researchers believe that boys with autism and ASD are at risk for poor bone development for a number of reasons. These factors are lack of exercise, a reluctance to eat a varied diet, lack of vitamin D, digestive problems, and diets that exclude casein, a protein found in milk and milk products. Dairy products provide a significant source of calcium and vitamin D. Casein-free diets are a controversial treatment thought by some to lessen the symptoms of autism.

A recent study due to be presented at IMFAR this year went to great lengths to ensure that children on the GF/CF diet did not miss out on essential nutrients.

The researchers took on the difficult yet crucial task of ensuring participants received needed nutrients, as children on gluten-free, casein-free diets may eat inadequate amounts of vitamin D, calcium, iron and high quality protein.

They also tried to control for the effects of different treatments and therapies that might confound the results of a dietary trial by ensuring that all the subjects received the same early intensive behavioural intervention during the trial. Twenty two children aged between thirty and sixtysix months were enrolled in the trial but only fourteen completed it. One withdrew after proving positive for celiac disease. Another had an iron deficiency and the rest were unable to adhere to all the study requirements.

The trial lasted for eighteen weeks. A month into the trial each child received a cleverly disguised snack containing either gluten, casein, a combination of both or neither and went on to receive three of each type of snack in random order at one week intervals. The snacks were disguised so that neither the researchers, the children, their parents nor their teachers could identify them. The result was that there was no difference to sleep patterns, bowel movements, language or behaviour in any of the children.

The authors acknowledge the obvious weaknesses in this study. it had a small sample size and did not include children with GI disorders. However it was very well designed and provides a model for future studies. Another study, Absence of urinary opioid peptides in children with autism (Cass et al 2008) found no evidence of increased urinary peptides i autistic children compared to non-autistic controls. This is in line with Hunter et al (2003).

All this suggests that unless your child has an obvious GI disorder you should not even consider a GF/CF diet. Even if there are GI problems it is highly unlikely that urinary peptides are to blame. And if the peptides are not there why use the diet? The commercial labs that claim to routinely detect these peptides in samples from autistic children stand in marked contrast to the university and hospital labs that have failed to detect these peptides even when using very sensitive testing procedures. The study by Cass et al found evidence that suggested the presence of peptides in 25 out of 68 samples from children with an ASD. However that was not the whole story.

By HPLC analysis alone, 25 urine samples from the autism/Asperger group were selected as showing peaks in approximately the correct locations to be opioid peptides. For all 25, MALDI-TOF MS analysis of the relevant fraction found no instances of ions of m/z corresponding to opioid peptides. These results indicate that the peaks observed on the HPLC trace were not opioid peptides.

Then we have the evidence from America. Ibrahim et al 2009 found no evidence of increased GI disease in autistic subjects. A recent review published by the American Association of Pediatrics found no evidence base for an increase in GI disorders or for the effectiveness of dietary interventions in autism.

This does not mean that there is no connection between autism and GI disorders. Ibrahim et al conclude that

As constipation and feeding issues/food selectivity often have a behavioral etiology, data suggest that a neurobehavioral rather than a primary organic gastrointestinal etiology may account for the higher incidence of these gastrointestinal symptoms in children with autism.

And the AAP review stressed that some so-called autistic behaviours may be indicative of gastro-intestinal distress and these children should not have these behavioural symptoms disregarded because they are autistic. As I wrote in my very first blog post

The first thing we have to be clear about is that the child’s symptoms are real. Some parents have had their worries dismissed because it is assumed that autistic children will have poor sleep patterns, scream a lot and be difficult to feed anyway. [...]

The second point is that some of these symptoms may be connected to a child’s autism. But we do not know how. If you are non-verbal and you have constant earache, you will head-bang. That does not mean that your earache caused your autism. Nor does it mean that alleviating your distress will cure your autism. It means you are autistic and you have an earache.

Anyone with an autism diagnosis should be given a full medical work up in case there are any other conditions that need treatment. Too often the diagnostic process stops when autism is identified. There are autistic children who have other conditions that may respond to safe, targeted biomedical interventions.

I would only add that “biomedical” in this context refers to evidence based medicine delivered by qualified professionals in a proper medical facility and not to the store front clinics of the alternative therapy business.

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