The gluten-free, casein-free diet in autism: results of a preliminary double blind clinical trial.
A gluten-free, casein-free diet does not improve autism symptoms and may thin bones in boys.
01Research in Context
What this study did
Fifteen children with autism ate a gluten-free, casein-free diet for twelve weeks. Parents and testers did not know which weeks were real diet and which were placebo food. Doctors watched autism symptoms and checked urine peptides each week.
What they found
Group scores for autism traits stayed flat. Urine peptides also showed no change. Some parents still felt their child did better, but the numbers did not back this up.
How this fits with other research
Tonnsen et al. (2016) ran the same kind of double-blind test ten years later and saw the same null result. The pattern is clear: GFCF does not help at the group level.
Matson et al. (2008) looked at bone growth in autistic boys. Kids on casein-free milk had much thinner bones. So while the diet shows no symptom benefit, it may carry a real bone risk.
Öztürk et al. (2026) pooled seventeen studies and still call the evidence “inconclusive.” Their review includes this 2006 trial, confirming its place in the “no clear benefit” pile.
Why it matters
You can stop recommending the GFCF diet for core autism traits. The science is consistent across labs and decades. If a family insists, warn about bone health and suggest calcium plus vitamin D screens. Spend your time on interventions with proven gains instead.
Want CEUs on This Topic?
The ABA Clubhouse has 60+ free CEUs — live every Wednesday. Ethics, supervision & clinical topics.
Join Free →Tell parents the diet has no group benefit and ask their pediatrician to check vitamin D and calcium if they still want to try it.
02At a glance
03Original abstract
This study tested the efficacy of a gluten-free and casein-free (GFCF) diet in treating autism using a randomized, double blind repeated measures crossover design. The sample included 15 children aged 2-16 years with autism spectrum disorder. Data on autistic symptoms and urinary peptide levels were collected in the subjects' homes over the 12 weeks that they were on the diet. Group data indicated no statistically significant findings even though several parents reported improvement in their children. Although preliminary, this study demonstrates how a controlled clinical trial of the GFCF diet can be conducted, and suggests directions for future research.
Journal of autism and developmental disorders, 2006 · doi:10.1007/s10803-006-0079-0