A growing body of research indicates that intervention, excluding foods containing the proteins, gluten and casein, from the diet of children diagnosed with an autism spectrum disorder may have a positive effect on behaviour and cognition.

In this single-blinded, randomised, matched-pair trial, we introduce a gluten- and casein-free diet to a group of pre-pubescent children diagnosed with an autism spectrum disorder who also present with an abnormal urinary profile. Following random allocation to a diet or non- diet group, the intervention group will follow the diet for eight months. The non-diet control group will at the same time continue with a normal diet.

At eight months an interim evaluation using standardised autism evaluation methods is used to ascertain whether predetermined thresholds for improvement in any of the assessment measures are met or surpassed by the diet group, compared with initial baseline measures.

If such thresholds are surpassed, the non-diet control group will also start on dietary intervention, with both groups following the diet for a further eight months. In the event such thresholds are not achieved, the intervention group will remain on diet for an additional four months, at which time a secondary interim analysis will be conducted.

After eight plus four months, if the threshold for improvement has been surpassed by the intervention group, the control group will then enter on dietary intervention, and all participants will follow the diet for another twelve months. In the event that no significant improvement has been found in the intervention group at eight plus four months compared to baseline measures, the study will be halted, and both groups will revert back to a normal diet.