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.
An extensive literature search was carried out to identify any randomised control trials of gluten and/or casein free diet as an intervention to improve behaviour, cognitive and social functioning in individuals with autism. Only three papers reporting on two randomised control trial were identified, two small scale trials the first with ten participants in each arm of the trial and the second with fifteen participants recruited into the trial. The results for the first study indicated that a combined gluten and casein free diet reduced autistic traits and the second study showed no significant difference in outcome measures between the diet group and the control group. This is an important area of investigation and large scale, good quality randomised control trials are needed. None of the studies reported on adverse outcomes or potential disbenefits.
There is evidence of widespread use by parents of complementary and alternative therapies (CAM) including exclusion diets for their children with autism. Despite this, there is a lack of evidence to support the use of gluten and/or casein free diet as an effective intervention for persons with autism and also a lack of research on potential harms and disbenefits of such diets. Despite the problems of maintaining the integrity of such diets in the community it is possible to carry out randomised control trials to address these questions and more and adequately powered trials are needed in this area.