The Autism Diet
If you can believe the many testimonials posted on the Web, a diet free of gluten and casein is a miracle treatment for autism. Parents of children suffering from the disorder, which is characterized by impaired social and communication skills, fervently describe astounding improvements that occurred as soon as they removed gluten (a mixture of plant proteins found in wheat, rye and barley) and casein (the main protein in dairy products) from their kids’ meals. Surveys indicate that as many as 40 percent of children with autism have been placed on special diets at one time or another. This enthusiasm is grounded more in hope than in science; so far researchers have no good evidence that dietary interventions can alleviate the symptoms of autism. Recently, however, investigators have launched the first rigorous tests of the diets, and the results may be available within a year.
The assumption behind the diets is that people with autism often have gastrointestinal abnormalities that allow unusual amounts of digestive by-products into the body (the so-called leaky gut syndrome). The by-products of gluten and casein, according to one hypothesis, disrupt brain function by altering opioid activity, which is involved in pain regulation and social bonding. Another theory posits that the gut leakage triggers a harmful immune response. These hypotheses are far from rock-solid; in fact, scientists have not even confirmed that people with autism have a higher-than-normal incidence of gastrointestinal problems. But the causes of autism are so poorly understood and the disorder is so variable that some investigators are willing to consider the possibility that gluten and casein may somehow exacerbate symptoms in some children, perhaps just by producing intestinal discomfort.
Unfortunately, the initial studies of diets that eliminate gluten and casein were badly flawed. Although half a dozen research groups reported improvements in behavior and cognition in autistic children after several months on the elimination diets, nearly all the studies lacked control subjects, individuals who continued to digest the suspect proteins. Because the researchers did not compare the restricted-diet children with a control group, they could not specify whether the behavioral and cognitive gains actually resulted from the diets, from the children’s maturation or from other therapies conducted at the same time.
The new studies, in contrast, involve control subjects and have a double-blind design: neither the researchers nor the parents will know whether the autistic children are consuming gluten or casein, so the evaluations of the children’s behavior will not be tainted by wishful thinking. In a study led by Robin Hansen of the University of California, Davis, all participants go on a gluten-free diet for two months; then, for the next two months, half the subjects eat daily snacks containing gluten while the other half get indistinguishable gluten-free snacks. Susan Hyman of the University of Rochester is running a similar study testing the behavioral effects of both gluten and casein. An investigation at the University of Pittsburgh Medical Center will monitor the effects of combining the gluten-free, casein-free diet with supplements of omega-3 fatty acids, another popular but unproved therapy for autism.
The researchers have run into some trouble recruiting autistic subjects. Many parents who are committed to the gluten-free, casein-free diet do not want to participate because their children may be included in a control group and receive the offending substances. “It’s a hard study to do, but it’s worth doing,” says Susan E. Levy, director of the Regional Autism Center at Children’s Hospital of Philadelphia.
--Originally published: Scientific American 296, 19-20. (April 2007)