The Gluten-Free/Casein-Free Diet: A Double-Blind Challenge Trial in Children with Autism.

Fourteen kids with autism ate a gluten-free, casein-free diet for four weeks. Then they got snack cookies twice a week for six weeks.

Half the cookies held real gluten and casein. Half were placebo. No one knew which was which. Parents, teachers and doctors rated behavior, sleep and bowel patterns after every snack.

Kids acted the same no matter which cookie they ate. Scores for hyperactivity, irritability and language did not budge.

Stool frequency, sleep hours and a urine gut marker also stayed flat. The diet challenge showed zero effect.

Öztürk et al. (2026) pooled 17 GFCF studies and still call evidence "preliminary." Our 2016 trial is one of the few double-blind tests in their pool, so the weak signal is not surprising.

Esteban-Figuerola et al. (2019) found autistic children already eat less dairy and protein. Removing even more with GFCF could widen those gaps.

Root et al. (2017) ruled out a urine marker once used to justify the diet. Together the three papers undercut both the mechanism and the need for GFCF.

You can now tell families that a rigorous challenge found no hidden reaction to gluten or casein. Save your clinical hours for diets that show benefit and watch calcium, vitamin D and protein if parents still wish to go GFCF.