Diet Therapy in the Treatment of Autism

First published in Naturopathic Doctor News and Review, January 2009

The treatment of Autism Spectrum Disorder (ASD) can be a challenging, prolonged and complicated process. It can also be extraordinarily rewarding when children begin to emerge from behind the autistic symptoms and engage in the world around them. Proper nutrition has been found to be one of the most successful interventions in the treatment arsenal. Reports based on parental and clinical observations, as well as supporting research studies have shown the benefits of numerous dietary protocols for autism. These include the gluten-free and casein-free diet, food allergy avoidance, anti-yeast diet, low oxalate diet, phenol-restricted diet and specific carbohydrate diet.


A cornerstone in autism dietary treatment has been the gluten and casein-free diet, or GFCF diet. The theory behind this approach is a hypothesized genetic-based peptidase deficiency, specifically diaminopeptidase IV or DPP-IV. The enzyme is either genetically missing or inactivated due to an autoimmune mechanism. This results in improper digestion of gluten and casein proteins and the formation of opiate-like peptides, casomorphine and gliadomorphine (Reichelt, K. and Knivsberg, A., 2003). These peptides enter the bloodstream across the “leaky gut” very commonly found in ASD kids, due to many factors including food IgG sensitivities, microbial overgrowth and gastrointestinal inflammation. Once in the circulation, the casomorphine and gliadomorphine compounds cross the inflamed blood-brain barrier, and attach to opiate receptors in the brain (Shattock, P. et al.,1990). Symptoms result such as insensitivity to pain, decreased awareness of the environment and general “spaciness”. These opioid peptides act as a drug interfering with motivation, emotions, perception, responses and brain development (McCandless, J., 2003). Gluten and casein are shown to be highly immune-reactive, with anti-casein and anti-gliadin antibodies present in children with autism (Vojdani, A., 2003).

When implementing this diet, it is suggested to discontinue dairy first for the first month, then gradually decrease gluten the following month in order to wean the child slowly from their preferred foods and decrease the likelihood of extreme withdrawal reactions. It is recommended to strictly adhere to the diet for 3 to 6 months because proteins, especially gluten, can take several months to be removed from the body. Children with this sensitivity frequently crave the dairy and gluten foods intensely, and self-restrict their diets. They often go through a withdrawal period for several months much like an addict would, with increased severity of behaviors, refusal to eat alternative foods, tantrums and insomnia.

Typical beneficial responses are that the child becomes more aware, engaged and responsive to their environment, with language improvements, decreased self-stimulatory behaviors, better eye contact and increased cognition. Often parents will report their child has come back to them and is no longer in their own world. Positive responses are seen in approximately 65% (range of 50-80%) of children put on this diet (Baker, S. and Pangborn, J., 2005). Clinically, I have found this to be the single most effective intervention and I always recommend parents try it at the start of treatment. An example is a two and a half year old boy with ASD who had dramatically improved eye contact, cessation of daily tantrums, increased responsiveness to communication, elimination of hyperactivity and decreased hand-flapping behavior after 1 month on the GFCF diet. Those who do not adhere to the diet do not respond as well to other therapeutics or make the same improvements in neurological symptoms compared to those on the GFCF diet (Knivsberg, A., et al, 2001).

A gluten and casein peptide test, which measures urinary excretion of gliadomorphine and casomorphine, helps to refine the diet by differentiating those children who may be more sensitive to either casein or gluten. Addition of specific digestive enzyme formulations containing the DPP-IV enzyme can also be of aid on a GFCF diet when dietary infractions occur, as they can alleviate or prevent flare-ups of symptoms due to gluten or casein reactions.


An important step in the ASD dietary protocol is to address problematic foods that may be causing inflammation. One method of evaluation is an IgG food allergy test, recommended at the outset of therapy to identify possible delayed food sensitivity reactions. Eliminating moderate to highly reactive foods can improve autistic symptoms especially related to digestive and behavioral problems. Studies have consistently found significantly elevated antibodies to food antigens in autistic children and higher levels of proinflammatory cytokines in food protein challenges (Jyonouchi, H. et al., 2002). More non-IgE mediated food allergies are also associated with ileal lymphoid hyperplasia found in children with autism (Wakefield, A., 2000). I treated one child who would hide under a table and growl every time he was upset, which stopped when taken off eggs that came up extremely high on his IgG food panel. Common autistic symptoms that improve with food allergy elimination diets are head-banging, self-stimulatory behaviors (aka “stimming”) such as hand flapping, sleep disturbances (frequent waking, nighttime screaming), self-injurious behaviors and aggression. Often chronic physical issues such as constipation, diarrhea, and dermatitis resolve. A trial elimination for at least 1 month, followed by a food challenge can be useful if obvious benefits are not seen initially. The most common allergens noted in children with autism are dairy, gluten, wheat, soy, eggs, corn and peanuts.


The anti-yeast or Candida diet is often necessary in ASD children due to intestinal yeast overgrowth, as noted on urine organic acid testing, stool analysis, or clinical history and symptoms. Restrictions of sugars, yeast, fermented and mold products, along with supplemental probiotics and anti-fungals are necessary to treat this often chronic issue. Children on the autism spectrum with yeast typically exhibit telltale behaviors: excessive stimming (both vocal and physical), cravings for high sugar foods, giddiness, inappropriate laughing, spaciness, or “drunk” behavior with loss of balance. Accompanying physical signs may also be present including excessive gas, bloating, constipation or diarrhea, and rashes. Introduction of this diet typically occurs with or just following GFCF diet implementation when fungal dysbiosis is evident in the autistic child. A three year old boy in my practice with ASD and seizure disorder responded remarkably to dietary intervention. At the outset of treatment he was non-verbal and experienced 10 seizures per day on average despite anti-convulsant medications. After one month on the GFCF diet, he was down to 3-4 seizures a day, and with subsequent anti-yeast therapy for 3 months, he became seizure free and began speaking.


The low oxalate diet was developed after discovering that a significant number of autistic children have excessive urine oxalate levels, with possible accumulations of oxalates in various body organs including the gastrointestinal tract, brain, blood-brain barrier, skin, heart, tendons, kidney, bone and eyes (Shaw, W., 2007). In addition, oxalates are known to bind with heavy metals forming complexes that are deposited in body tissues. Pockets of oxalate crystals can damage tissue, cause oxidation and lead to diverse signs such as digestive pain, toe-walking, eye poking, white skin lesions, discomfort on urination, excessive urinary frequency, enuresis, cloudy urine, genital discomfort and rubbing, and “sandy” stools. Restrictions of high oxalate foods such as spinach, soy, peanuts, chocolate, and berries have been found to be beneficial in these cases. Limiting total dietary oxalate intake to less than 50 mg per day is recommended. Reducing vitamin C foods or supplements is not necessary in the presence of high urinary oxalic acid, unless there is increased free copper or iron to act as oxidative catalysts for the formation of oxalate via ascorbate (Shaw, W., 2007). High urinary oxalic acid levels are often found in conjunction with elevated yeast, as the Candida can induce oxalate formation, therefore an anti-yeast protocol is suggested when oxalate values are raised. In addition, supplementation with taurine and calcium citrate helps to reduce oxalate absorption in the digestive tract.


Impaired sulfation capacity is documented in autism, with some children displaying sensitivity to phenolic amines in foods due to deficient function of the phenylsulphotransferase (PST) enzyme (Waring, R., 2000). For this subset, restriction of high phenol foods may be beneficial which includes bananas, chocolate, cheese, apples, grapes, and tomatoes. The phenol-sensitive ASD child will exhibit abnormal behaviors such as hyperactivity, red face and ears after consuming these foods. The PST enzyme is also responsible for metabolism of amine neurotransmitters like dopamine and epinephrine, which are often dysfunctional in autism. As with the previous dietary interventions, a trial of elimination then re-challenge of the suspected offending foods can aid in determining whether it may be a beneficial therapy. Addition of an enzyme supplement containing xylanase specific for phenol digestion can reduce symptoms in addition to the dietary recommendations.


The newest diet is the Specific Carbohydrate Diet (SCD), originally proposed as a therapeutic diet for inflammatory bowel disease. By restricting foods contributing to intestinal dysbiosis, the goal of this intervention is to starve pathogenic microorganisms and reduce inflammation in the gastrointestinal tract. The SCD limits complex carbohydrates particularly disaccharides, relying on protein, fats and simple carbohydrates to heal the gut. Abnormal carbohydrate digestive enzyme activity has been found in almost 60% of ASD children studied (Horvath, K. et al, 1999). Partially digested sugars or starches cause inflammation, dysbiosis, excessive mucus production, and promote leaky gut syndrome.

Many children who do not respond well to previous diet protocols often benefit from the SCD, especially those ASD children with significant chronic digestive problems, or “gut kids”. I treated three siblings with autism who previously tried the GFCF and food allergy avoidance diets with limited success, all responded remarkably to the SCD. Their chronic diarrhea resolved, and behavior changes were significant, including improved communication, decreased tantrums, more emotional regulation, better sleep, less hand flapping, and improved eye contact. On average 69% of the children improved on the Specific Carbohydrate Diet, according to a parent-report survey, more than with any other autism dietary protocol. (Baker, S. and Pangborn, J., 2005)


It is important for the health and healing of children with autism to implement specific dietary changes determined by individual needs and responses. Nutritional therapy has the capacity to make significant, long-lasting changes in the abnormal biochemistry, as well as the physical and behavioral expression of ASD. Addressing dietary factors must be a key component of any treatment plan for a child on the autism spectrum.


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