A Cochrane review included 2 studies with a total of 35 subjects. Meta-analysis was not possible. There were only 3 significant treatment effects in favour of the diet intervention: overall autistic traits (mean difference, MD -5.60, 95% CI -9.02 to -2.18); social isolation (MD = -3.20, 95% CI -5.20 to -1.20) and overall ability to communicate and interact (MD 1.70, 95% CI 0.50 to 2.90). In addition 3 outcomes showed no significant difference between the treatment and control group and it was not possible to calculate mean differences for 10 outcomes because the data were skewed. No outcomes were reported for disbenefits including harms.
Comment: The quality of evidence is downgraded by inconsistency (variability in results across studies), by imprecise results (few patients and wide confidence intervals) and by potential reporting bias (only few small trials reported).