Can Wheat or Dairy Cause Autism?

Can gluten or casein (wheat or dairy) actually cause autism? Books and websites galore recommend that people with autism eliminate wheat and dairy from their diets. Some therapists, parents, doctors and writers swear they know a child who, as a result of this diet, has completely "recovered" from autism, and the child no longer qualifies for an autism spectrum label. Mainstream doctors and researchers, however, tend to be skeptical about claims of "cures" as a result of dietary change.
Could wheat and dairy actually be the culprits for at least some cases of autism?

Do Gluten and Cassein Cause Autism? The Opiate Theory

A popular theory follows this logic:

• Wheat gluten and cassein contain proteins which break down into molecules that resemble opium-like drugs.
• Children with autism have compromised digestive systems, including "leaky guts." Leaky gut syndrome is a somewhat controversial diagnosis; in essence, it means that a person's intestines are unusually permeable, allowing extra-large molecules (such as proteins) to leave the intestines. Thus, instead of simply excreting these large opium-like molecules, autistic children absorb the molecules into their bloodstreams.
• The molecules travel to the brain, where they induce a state similar to that of a drug-induced "high."
• When wheat and cassein are removed from the diet, the child no longer experiences the high, and his or her behaviors and abilities radically improve.

A corollary to this theory states that when a child's preferred diet is mostly items containing wheat and dairy (pizza, crackers, milk, ice cream, yogurt, sandwiches - in short, what we often think of as "kid food"), that proves that the child is addicted to the opiate-like molecules and would benefit from the GFCF diet.

Does the Opiate Theory of Autism Hold Any Water?

It's not easy to track down evidence for each element of the opiate theory. Here, however, is the information I've been able to glean so far:

• Wheat and dairy do in fact break down into peptides which, in fact, look a lot like opium-like drugs. These are called gluteomorphines and cassomorphines.
• Some children with autism (though by no means all) do have gastrointestinal issues. A subgroup of these children have leaky intestines.
• Some studies show that the peptides in question are found in unusually high amounts in the urine of autistic children - but those studies included only children with existing gastrointestinal issues. A study that included a broader group of autistic children did not show an increased level of peptides in the urine.
• There have been studies showing that the brains of rats injected with casomorphines are activated in areas affected by autism (though there are still big questions about which areas of the brain really are affected by autism, which makes me question the outcome of that particular study).
• I could not find any evidence to show that gluteomorphines and casomorphines actually cause autistic-like behaviors. Several studies have looked at the impact of Naltrexone (not approved in the U.S.) - a drug which blocks the impact of gluteomporphines and casomorphines on the brain. The researchers found that there was little support for the idea that Naltrexone is effective in treating symptoms of autism.
• Many studies have shown that a GFCF diet is effective in treating symptoms of autism, though quite a few equally credible studies seem to show otherwise.

To verify my own research, I checked in with Dr. Cynthia Molloy, M.D., Assistant Professor of Pediatrics at the Center for Epidemiology and Biostatistics Cincinnati Children's Hospital Medical Center. Here is her response:

The dietary proteins could reasonably have an impact on GI issues, but even that has not been clearly demonstrated. There is no empiric evidence to support a causative relationship between these proteins and autism. It is conjecture to draw the conclusion that a child is experiencing an opiate effect from foods because he craves them.

Weighing all of this evidence, it is my opinion that the opiate theory of autism holds very little water - though the GFCF diet itself may hold some promise.

Why Does GFCF Seem to Work?

GFCF diets are difficult and expensive to administer. They require a lot of dedication and knowlege, and most professionals suggest that the diet be implemented over at least three months. Given all of this, it's possible that parents who desperately want to see improvement could report improvement that may or may not actually be present. In addition, many children do gain new skills over the course of three months, with or without special diets.

But there's more to the story that just wishful thinking. Allergies to gluten and cassein are not uncommon, and those allergies often manifest themselves in diarrhea, constipation, bloating and other symptoms. About 19 to 20 percent of autistic children seem to have significant gastrointestinal issues.
If these issues are caused by gluten and/or cassein, then they would certainly be significantly improved by the diet. By removing a source of constant discomfort and anxiety, parents may well be opening the door to improved behaviors, better focus, and even lowered anxiety.
 
_Sources:
Christison, G.W., and K. Ivany. 2006. "Elimination diets in autism spectrum disorders: any wheat amidst the chaff?" J Dev Behav Pediatr. 27(2 Suppl):S162-S171.
Cornish, E. 2002. "Gluten and casein free diets in autism: a study of the effects on food choice and nutrition." J Hum.Nutr.Diet. 15(4):261-269.
Elchaar, G.M., et al. 2006. "Efficacy and safety of naltrexone use in pediatric patients with autistic disorder." Ann.Pharmacother. 40(6):1086-1095.
Elder, J., et al. 2006. "The Gluten-Free, Casein-Free Diet in Autism: Results of a Preliminary Double Blind Clinical Trial." Journal of Autism and Developmental Disorders 36:413-420.
Erickson, C. et al. 2005. "Gastrointestinal Factors in Autistic Disorder: A Critical Review." Behavioral Science Volume 35, Number 6 / December, 2005
[url link=http://autism.healingthresholds.com/]Healing Thresholds website
Interview with Dr. Cynthia Molloy, M.D., M.S. Assistant Professor of Pediatrics, Center for Epidemiology and Biostatistics, Cincinnati Children's Hospital Medical Center, March 13, 2007.