Autism and Diet 1: The Casein-Gluten Free Diet

“Though it be honest, it is never good
To bring bad newes: give to a gratious Message
An host of tongues, but let ill tydings tell
Themselves, when they be felt”

Cleopatra to the Messenger in Antony and Cleopatra, William Shakespeare

The final details of the story linking diet and autism remains to be written, but an great deal is already known. Many parents of children with autism spectrum disorders believe such a link exits, varying from the firmly held conviction that vaccines together with diet caused their child’s autism, to other parents who subscribe to the idea that specific di
etary indiscretions can cause worsening of their child’s autism symptoms though they may not have caused autism. To be the bearer of the news that such a link may not exist, at least not in the sense that diet is causally related to the core symptoms of autism, may make me an unwelcome messenger. But in light of the objective scientific evidence, that conclusion seems apt. After exploring the evidence, it is worth thinking together about the reasons the idea that dietary changes may improve autism functioning is so appealing, especially to parents. That will be discussed in the second part of this report.

The idea that diet and healthy living can overcome a developmental disability isn’t new. The best known advocate of this notion was Johann Guggenbuhl, a young Swiss physician who in 1841 constructed a mountain retreat Abendberg, near Berne for children with Cretinism. Guggenbuhl claimed his diet, exercise and clear mountain air cured individuals of Cretinism (congenital hypothyroidism). Individuals born lacking sufficient thyroid hormone develop moderate to severe intellectual and physical disability, healthy diet or not. Guggenbuhl travelled all over Europe raising money for his mountain retreat, fleecing wishful parents and other donors. Eventually, however, visitors to the Abendberg discovered neglect and abuse, due in part to Guggenbühl's frequent and prolonged absences, and it was discovered that his claims of cures was false. Guggenbuhl was eventually prosecuted by Swiss authorities and the Abendberg was closed.

The Shot Heard Round the Autism World

Before 1998, parents of children with autism expressed limited concern about their children’s diet, other than noting their children tended to be very finicky eaters. Doctors seemed to have had a similar reaction to diet and autism. I did a thorough review of medical literature from 1988-98 and found only 4 scientific publications involving children with autism and diet. Two suggested diet may be related to autism behavioral symptoms and two failed to find any relation to autism. I have been unable to uncover any publication suggesting diet could cause autism before 1998, the year Karoly Horvath and his co-workers in Maryland, and Andrew Wakefield and colleagues in London, separately published articles in medical journals proposing a link between gastrointestinal functioning and autism. Following appearance of those two inflammatory articles pandemonium broke out within the autism parent community, with wild claims circulating the globe via the internet, literally within hours, about the cause of autism. Horvath’s and Wakefield’s claims suggested there was a readily preventable cause of autism, namely an immune disorder caused by Measles-Mumps-Rubella vaccination, which turned out was false. But these beliefs stick to the parent autism community wall like al dente spaghetti.

Horvath and Wakefield are gastroenterologists with no prior autism background. Horvath injected three children who he said had autism with secretin, a pancreatic hormone used in testing GI function, because the children had gastrointestinal symptoms. Five weeks after the secretin test Horvath said their autism symptoms dramatically improved. There were no standardized independent assessments of the children by an unbiased observer before or after administration of secretin. Dozens of subsequent independent studies failed to reveal any relationship between the pancreatic hormone, secretin and autism symptoms. Horvath’s results were either imagined or were a fluke.

Wakefield studied intestinal tissue and spinal fluid from children with autism who were referred to his GI clinic because they had gut symptoms. They were not referred because they had autism. On laboratory examination he found physical abnormalities in the intestinal tissue among some children with autism who had gastrointestinal symptoms. He asked the parents if their autism symptoms and diagnosis first appeared following measles-mumps-rubella vaccination, and most of the parents reported that they thought their child’s autism symptoms did arise that way. In other words, Wakefield suggested to the parents that there was a link between MMR immunization and autism, and most agreed. Wakefield hypothesized that MMR vaccine damaged the gut lining making it permeable to toxic bacteria. What he didn’t tell the parents, was that he was being paid by an anti-vaccine group to conduct the study. He was hardly an unbiased professional observer. There were numerous other methodological and ethical flaws in his study, that have been investigated by the UK General Medical Council, which, as a result, disbarred Wakefield from practicing medicine in the UK in 2010. Ten of the 13 authors of the Wakefield study article asked that their names be removed from the article. The journal Lancet withdrew the Wakefield article from its pages.

A large number of independent studies in several countries by unrelated groups of researchers have failed to find a relation between MMR vaccination and autism prevalence. In addition, most studies by other independent researchers have failed to find a reliable immune disorder or physical gut differences in children with autism, as reported by Wakefield. Only Wakefield and his collaborators (4-5 articles) and Jyonouchy at the University of Minnesota (two artlcles), found such immune disorder relationships. Other independent researchers have failed to find such a relationship. It is true that children with autism tend to have more problems with constipation or diarrhea than typically developing comparison children, but not more than other children with developmental disabilities, but that may be due to many other causes unrelated to vaccines or autism.

Casein-Gluten Free Diet

Caseine is the main protein present in milk and (in coagulated form) in cheese. Gluten is a protein present in cereal grains that is responsible for the elastic texture of dough. A mixture of two proteins, it causes severe gastrointestinal illness in people with celiac disease, usually of genetic origin. Celiac disease affects about 1% of Americans. Celiac disease (allergy to gluten) is not more common among individuals with autism than matched control children. A specialized diet free of casein and gluten has been widely used by parents in the belief that it would counteract these alleged but unsubstantiated immune-related gut abnormalities. A considerable industry has emerged providing CGF dietary products for parents seeking them for their children, with total annual sales exceeding $1.7 billion.

CGFD: Empirical Evidence

It is possible the CGF diet could reduce behavioral symptoms associated with autism by another mechanism even if there are no physical gut abnormalities as Wakefield claimed, so perhaps it is worth evaluating. There have been several controlled studies of the CGF diet, mostly failing to find an effect of the diet, and one recent study from the UK that lacked a control comparison group, that reported improvements in some autism symptoms associated with CGFD. An American consensus panel of autism and GI specialists chaired by Timothy Buie, a gastroenterologist from Harvard University concluded, “that evidence-based recommendations are not yet available. The consensus expert opinion of the panel was that individuals with ASDs deserve the same thoroughness and standard of care in the diagnostic workup and treatment of gastrointestinal concerns as should occur for patients without ASDs.” In other words, any child with gastrointestinal symptoms should be evaluated and treated for those symptoms, but there is no indication that those symptoms are specifically related to autism.

The Cochrane Database System Review conducted an analysis of controlled CGFD studies in 2008. They found two small Randomized Clinical Trials. There were only three significant treatment effects across the two studies favoring the CGFD diet intervention: overall autistic traits, social isolation, and overall ability to communicate and interact. Three other outcomes showed no significant difference between the treatment and control group. An example is the Elder et. al. (2006) study that tested the efficacy of a gluten and casein free diet in treating symptoms of autism in a randomized, double-blind study. Over 12 weeks the sample of 15 children showed no significant symptoms differences between being on and off the diet, though several parents reported improvements regardless of diet condition. Cornish (2002) studied nutrient intakes of children who were receiving gluten and casein free diets and a comparison group of children with ASDs that was not. Half of the children in the gluten-casein free diet group were deficient for zinc and calcium. Arnold et. al. (2003) studied dietary plasma amino acid profiles of 36 children with ASDs. Ten children were on gluten-casein free diets. No consistent amino acid profile was found across children with ASDs. Children on the GCFD had more types of essential amino acid deficiencies and lower plasma levels of the essential amino acids tyrosine and trytophan, which are involved in serotonin metabolism. The role of dietary abnormalities in GI symptoms including diarrhea and constipation among children with ASDs was unclear.


1. Prior to the Horvath and Wakefield articles published in 1998 few parents of children with autism or their doctors expressed concern about diet and gastrointestinal problems. Many parents noted their children were finicky eaters, but not that they had unusual gastrointestinal problems.

2. Horvath’s and Wakefield’s claims about gut abnormalities that are specific to children with autism appear to be false. Both claims (secretin cures autism) and MMR vaccine, gut problems are associated with increased autism prevalence have not been substantiated when studied by others. While some children with autism as well as those with other developmental disabilities have intestinal problems, there is no evidence there are autism-specific gut abnormalities as claimed.

3. Celiac Disease (gluten intolerance) is about as common among children with autism as among other children. The rationale for the Casein-Gluten Free Diet based on presumed gut abnormalities, including gluten intolerance in autism lacks empirical support. Recent research has indicated that proposed internal opioid chemicals are released in the gut by gluten in the diet, and are linked to GI and autism symptos, have been found to be false.

4. There have been two controlled clinical trials with the CGFD yielding little evidence of significant improvements or gains associated with the diet. A national consensus conference held in the US in 2009 concluded there was insufficient evidence to recommend the diet. Several other studies without random assignment have failed to find autism symptom changes as a function of being on or off the CGFD.


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Autism & Diet 2: Why Autism Parents are Drawn to Special Diets