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Two different connections between diet and autism

The hypothesis that gluten and milk affect autism has existed for several decades, but has never received any proper attention. There is also a comorbidity between epilepsy and autism. For epilepsy, a strict low carbohydrate diet has been proven to have an effect, but no large studies have ever examined whether this kind of diet might also help in autism. The Dietary Science Foundation wants to evaluate both of these connections between diet and autism.

The theory that the cereal protein gluten and milk protein casein might affect autism has a long history. The scientific literature is full of small studies that examine the connections, but results point in different directions. The theory recognizes the fact that children with autism relatively often have gastrointestinal problems. This seems to apply to a subgroup of children. In a survey from 2013, parents of thousands of children with an autism spectrum diagnosis answered questions about constipation, diarrhea and flatulence. Gastrointestinal problems were found to be eight times more common in children with autism compared with children who developed normally. In 2012, in a study of 14,000 children with an autism spectrum diagnosis, medical records showed gastrointestinal problems to be 2.6 times more common. Several more studies have indicated that around 40 percent of all children with autism have trouble with their bowels. There are also a great number of studies that show that the children’s intestinal flora is disturbed.

Some researchers believe that a disturbed bowel leads the intestines to leak, allowing pieces of milk and gluten proteins to enter the bloodstream. When they reach the brain, they can, according to this theory, serve as opium-like substances (opioids) that interfere with signals between nerve cells.

Can food that is free from gluten and milk protein help a subgroup?

This theory is controversial in the scientific community. But new research shows that people with autism are more likely to have an immune system that reacts to gluten. A Swedish study from 2013 showed that gluten-related antibodies in the blood were four times as common. Two similar studies were published the same year with the same results. In one study, milk protein antibodies were also seen to be more common in people with autism.

When researchers have previously studied whether a gluten and dairy-free diet can help in autism, all the children with autism were put in the same group. In these studies, it seemed like some children were helped by the diet, while others noticed no effect at all. There is a need for high-quality studies in which only children carrying antibodies to gluten and milk proteins are included.

Can a diet that helps with epilepsy help with autism?

Another question that needs an answer is whether the diet that helps a subgroup of children with epilepsy can also help with autism. Children with epilepsy are often helped by an extremely strict form of low-carbohydrate diet called a ketogenic diet. Around one-third of all children with autism also have epilepsy ( The more severe the autism a child has, the greater the risk that epilepsy will also develop. When researchers look for genetic changes that are associated with severe epilepsy, they also find a large overlap with the autism spectrum. Just as with epilepsy, the cellular power plants, the mitochondria, are often dysfunctional in autism. This does not apply to all autistic children, but to many of them. The more debilitated the mitochondria are, the greater the degree of autism that may develop. Just as with epilepsy, there are high levels of free radicals inside the cells, and levels of a protective substance called glutathione is low.

Because there are so many similarities between the two diseases, Greek researchers tested a ketogenic diet as a treatment for autism early in the 2000s. On the island of Crete, an unusually high number of children are diagnosed with autism. Thirty children tried a strict low-carbohydrate high-fat diet and twenty-three of them managed to stick to it. Five of the twenty-three saw no effect and stopped the diet after a short time. Of the eighteen remaining children, all were improved. Two boys were so much better that they could start attending a regular school, eight of the children had a moderate improvement, and eight more saw a small improvement. In total, a quarter of the children made a large enough improvement that it was worth it to follow the strict diet; among other things it became easier for them to concentrate and learn.

When the results were published, the Greek researchers wrote that the topic required further exploration. But so far no similar studies have been conducted. In 2013, researchers reported that a ketogenic diet works for autism-like behaviors in mice. There is a need for scientific studies that evaluate whether a subgroup of children with autism can be helped by a strict low-carbohydrate diet. Autism is a disability that is on the increase among children and it’s important to find effective treatments.

Other facts: Several connections between gluten and the brain

There is a rare form of celiac disease called gluten ataxia where patients have gluten-related antibodies in their blood. People with ataxia lose their motor skills. Some are no longer able to walk and need wheelchairs. The reason is that the immune system attacks and destroys part of the cerebellum.

A large registry study from Sweden shows an association between celiac disease and epilepsy; epilepsy is 40 percent more common among people who have gluten intolerance. Nobody knows yet why these connections exist.


Autism on the increase among children:

Prevalence of autism in a US metropolitan area (2003)

Prevalence of autism spectrum disorders–Autism and Developmental Disabilities Monitoring Network, 14 sites, United States, 2008 (2012)

The prevalence of autism spectrum disorders in toddlers: a population study of 2-year-old Swedish children (2012)

Studies about how a gluten and dairy-free diet affects children with autism:

Gluten- and casein-free dietary intervention for autism spectrum conditions (2012)

Gluten- and casein-free diets for autistic spectrum disorder (2008).

The ScanBrit randomised, controlled, single-blind study of a gluten- and casein-free dietary intervention for children with autism spectrum disorders (2010).

Children with autism commonly have problems with their bowels and intestinal flora:

Gastrointestinal Problems in Children with Autism, Developmental Delays or Typical Development (2013).

Parent-reported gastro-intestinal symptoms in children with autism spectrum disorders (2013)

The prevalence of gastrointestinal problems in children across the United States with autism spectrum disorders from families with multiple affected members (2011)

Reduced incidence of Prevotella and other fermenters in intestinal microflora of autistic children (2013).

Impaired carbohydrate digestion and transport and mucosal dysbiosis in the intestines of children with autism and gastrointestinal disturbances (2011)

Gastrointestinal microflora studies in late-onset autism (2002) 

People with autism have gluten-related antibodies in their blood:

Increased risk of epilepsy in biopsy-verified celiac disease: a population-based cohort study (2012).

A nationwide study of the association between celiac disease and the risk of autistic spectrum disorders (2013)

Antibodies against food antigens in patients with autistic spectrum disorders (2013)

Markers of Celiac Disease and Gluten Sensitivity in Children with Autism (2013)

Studies that show that intestinal flora can influence behavior:

Microbiota modulate behavioral and physiological abnormalities associated with neurodevelopmental disorders (2013)

Toward effective probiotics for autism and other neurodevelopmental disorders (2013)

Normal gut microbiota modulates brain development and behavior (2011)

About a ketogenic diet and epilepsy:

Ketogenic diet for the treatment of refractory epilepsy in children: A systematic review of efficacy (2000)

A decade of the modified Atkins diet (2003-2013): Results, insights, and future directions (2013)

Neuroprotective and disease-modifying effects of the ketogenic diet (2006).

About dysfunctional mitochondria in epilepsy and autism:

Mitochondrial dysfunction in epilepsy (2013).

The ketogenic diet increases mitochondrial glutathione levels (2008).

Mitochondrial reactive oxygen species regulate the strength of inhibitory GABA-mediated synaptic transmission (2014)

Mitochondrial dysfunction in autism spectrum disorders: a systematic review and meta-analysis (2012).

Mitochondrial dysfunction in autism (2010).

About the connections between epilepsy and autism:

Epilepsy beyond seizure: a population-based study of comorbidities (2014)

The co-morbidity burden of children and young adults with autism spectrum disorders (2012).

De novo mutations in epileptic encephalopathies (2013).

Studies about a ketogenic diet and autism:

Application of a ketogenic diet in children with autistic behavior: pilot study (2003)

Ketogenic diet improves core symptoms of autism in BTBR mice (2013)

A Review of Traditional and Novel Treatments for Seizures in Autism Spectrum Disorder: Findings from a Systematic Review and Expert Panel (2013)