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Gluten and Casein Free Diets for Autism Spectrum Disorder
There is evidence of widespread use by parents of alternative treatments for treating and improving symptoms in children with autistic spectrum disorders (ASDs), and these are generally perceived as risk free. Among these, the most commonly used is the gluten-free, casein-free diet (GFCF). But is there an evidence base to support the use of this type of elimination diet?
The Scientific Reviews
In 2008, a Cochrane review, one of the best standard types of review, concluded there was a lack of evidence to support the use of gluten and/or casein free diets as effective treatments for persons with autism, and also a lack of research on potential harms of such diets. In this review, an extensive literature search was carried out to identify any randomised control trials of gluten and/or casein free diets as interventions to improve behaviour, cognitive and social functioning in individuals with autism. However, only 2 small scale randomised control trials were identified.
A later, less rigorous review published in 2010 also concluded that the evidence did not support use of gluten-free and/or casein-free diets in the treatment of ASDs. Interventions included both gluten– and casein-free diets given for between 4 days and 4 years (mean 10 months). Most participants were male (67%), and the age of the subjects ranged from 2- 17 years. The studies in the review were poor quality and had very small sample sizes (188 subjects for all trials together). None of the reviewed studies were assessed as providing conclusive evidence; 7 studies reported positive results (but the authors reported all studied with positive results as low quality studies), 4 reported negative results, 2 reported mixed results and in one study the effect of the intervention could not be determined.
Parents try Gluten & Casein Free Diets for ASD
Since that time, there remains reported anecdotal widespread use. In a recent UK survey, more than 80% of parents of children with ASDs reported some kind of dietary intervention for their child. Twenty nine percent had tried a gluten-free and casein-free diet of whom 20-29% reported improvements in symptoms. But this is self-reported so risk of measurement error is high.
A 2014 review from the University of Valencia looked at studies published from 1970 to 2013. The authors concluded that there are simply too few studies investigating the relationship between gluten-free and casein-free diets and improvement in ASD symptoms to be regarded as providing sound scientific evidence. Only 4 good quality randomised controlled trials were included, and even these were based on small sample sizes, reducing their validity.
Limited & Weak Evidence
The latest review published this week in Nutrition and Dietary Supplementsconsidered research published in the last 10 years from 2005-2015. One of the extraordinary findings in this paper were that the authors included 10 published reviews, yet only 5 of these were judged to be good quality randomised controlled studies. Of these (listed below), only the Whiteley study showed a significant improvement with the gluten-free and casein-free diet. Interestingly this was the only intervention undertaken for longer than 3 months.
The evidence on this topic is currently limited and weak. A number of authors have suggested that restrictive gluten-free and casein-free diets should be implemented only where a food allergy or intolerance has been diagnosed. Should a child with ASD experience acute behavioural changes seemingly associated with changes in diet, clinicians should consider testing the child for allergies and food intolerances and subsequently eliminate identified allergens from their environment as much as possible.
The science here needs to move forward so evidence-based guidance can be more clearly communicated to concerned carers looking for symptom improvement. Whilst well-controlled gluten-free and casein-free dietary trials may be difficult to conduct, they remain desperately needed in order to inform clinical treatment decisions. Until such evidence is available, it is important for carers and health professionals to recognise that a gluten-free and casein-free diet is unlikely to be a ‘cure.’
Any decision by carers to adopt this type of elimination should be treated with caution. The few studies of potential harmful effects of a GFCF diet in children with autism have been mainly related to two aspects, nutritional adequacy and physical development, with some suggestion of adverse effect. The nutritional adequacy of diets should therefore be carefully monitored. Carers considering exclusion diets should consult with a registered dietitian. Dietetic support can also be sought to provide tailored, holistic advice and support on achieving a healthy, balanced diet including the use of vitamins and minerals to supplement the diet if needed and advice on dietary approaches to gut problems.