Background: 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. Research has reported abnormal levels of peptides in the urine and cerebrospinal fluid of people with autism.
Objectives: To determine the efficacy of gluten and/or casein free diets as an intervention to improve behaviour, cognitive and social functioning in individuals with autism.
Search strategy: The following electronic databases were searched: CENTRAL(The Cochrane Library Issue 2, 2007), MEDLINE (1966 to April 2007), PsycINFO (1971 to April 2007), EMBASE (1974 to April 2007), CINAHL (1982 to April 2007), ERIC (1965 to 2007), LILACS (1982 to April 2007), and the National Research register 2007 (Issue1). Review bibliographies were also examined to identify potential trials.
Selection criteria: All randomised controlled trials (RCT) involving programmes which eliminated gluten, casein or both gluten and casein from the diets of individuals diagnosed with an autistic spectrum disorder.
Data collection and analysis: Abstracts of studies identified in searches of electronic databases were assessed to determine inclusion by two independent authors The included trials did not share common outcome measures and therefore no meta-analysis was possible. Data are presented in narrative form.
Main results: Two small RCTs were identified (n = 35). No meta-analysis was possible. There were only three significant treatment effects in favour of the diet intervention: overall autistic traits, mean difference (MD) = -5.60 (95% CI -9.02 to -2.18), z = 3.21, p=0.001 (Knivsberg 2002) ; social isolation, MD = -3.20 (95% CI -5.20 to 1.20), z = 3.14, p = 0.002) and overall ability to communicate and interact, MD = 1.70 (95% CI 0.50 to 2.90), z = 2.77, p = 0.006) (Knivsberg 2003). In addition three outcomes showed no significant difference between the treatment and control group and we were unable to calculate mean differences for ten outcomes because the data were skewed. No outcomes were reported for disbenefits including harms.
Authors' conclusions: Research has shown of high rates of use of complementary and alternative therapies (CAM) for children with autism including gluten and/or casein exclusion diets. Current evidence for efficacy of these diets is poor. Large scale, good quality randomised controlled trials are needed.