May 5, 2010 -- The use of gluten-free and casein-free diets to treat autism is increasingly popular among families, but researchers who reviewed 14 published studies on the diets say science does not back them up as useful.
"The evidence that has been collected does not support the use of the diets as a treatment for autism," study researcher Austin Mulloy, a doctoral student at the University of Texas at Austin, tells WebMD.
"A number of studies have been done and they are all inconclusive about the diets' effectiveness," he says. The review is published in the summer edition of Research in Autism Spectrum Disorders.
About one in 110 children in the U.S. has autism spectrum disorder, a group of neurodevelopmental disorders that include autism as well as Asperger's syndrome and other forms that involve difficulties in social relationships and communication.
Autism diets are quite popular, Mulloy says. Studies and surveys show that 17% to 27% of parents use a special diet to help treat autism or autism spectrum disorders.
Searching for the Cause of Autism
The cause of autism remains unknown; multiple genetic defects are thought to be involved in the disorder, along with an environmental trigger.
One theory suggests that some children have insufficient enzyme activity in their gastrointestinal tracts, resulting in incomplete digestion of the proteins casein and gluten. Casein is found in milk and other dairy products. Gluten is found in wheat, barley, and other grains.
In a normal GI tract, enzyme activity breaks down proteins into peptides and then into amino acids. When the gluten and casein aren't adequately broken down, the peptides derived from them can leak into the bloodstream and eventually travel to the brain, proponents of this theory say, resulting in the symptoms.
Parents who have put their children on the gluten-free, casein-free diets often post enthusiastic success stories on web sites, sometimes describing the changes as miraculous.
Reviewing the Evidence on Autism Diets
To test evidence about the diets, which Mulloy says can be expensive and time-consuming to follow, the researchers searched medical literature for scientific studies of the effectiveness of the autism diets.
From a total of 134 studies, they narrowed the number to 15 papers involving 14 studies. They used a number of criteria, such as whether the researchers evaluated how the diet helped symptoms and involved the dietary intervention of foods that are casein-free, gluten-free, or both.
Of the 14 studies that were reviewed, one looked at just gluten-free diets, another at just casein-free, and the others looked at both gluten-free and casein-free diets.
"None of the reviewed studies were capable of providing conclusive evidence," the researchers write.
Just as importantly, Mulloy tells WebMD, ''there are several known harms that should be taken into consideration." There is the possibility of nutritional deficiencies, especially calcium, he says.
Parents may also spend much time and money on the diets, he says, and those resources could be better spent on more proven treatments.
''The final negative effect is the diet can be stigmatizing," he says. For instance, ''the child may not be able to eat birthday cake at a birthday party.''
He does see a potential role for the diets, however. "If a child is experiencing acute behavioral changes associated with diet, or if the doctor has identified allergies or food intolerance associated with gluten or casein, then it is worthwhile to consider use of the diet," he says.
''This study summarizes what a lot of the science has been saying for awhile, which is there is not a lot of good evidence to support using this diet as frequently as parents report using it," says Daniel Coury, MD, medical director of the Autism Treatment Network and chief of developmental and behavioral pediatrics at Nationwide Children's Hospital in Columbus, Ohio.
That said, Coury tells WebMD, "I think there is a role for it in some children." On that list, he says, would be children with autism who also have celiac disease, marked by problems digesting gluten. ''Children with autism could certainly have celiac disease, which responds well to the gluten-free diet," he says.
The take-away message for parents, in Coury's view, is: "If [parents] are spending a good deal of their income or time investing in this diet instead of investing in other treatments shown to be more effective, that would not be good."