Parents have been implementing special diets for years to help improve the health of and reduce symptoms in their children with autism. Given the number of cookbooks and blogs dedicated to this subject, it appears the gluten-free/casein-free (GFCF) diet was and still is the most well known diet for symptom reduction. However, there are other diets to choose from, and often, the gluten-free/casein-free diet only goes so far. How is a parent to know which diet is best for a child with autism?

Limited Research on Therapeutic Diets

Despite some parents being in the know about healing diets, peer-reviewed medical research has been decades late to the game, probably due to the fact that there is very little money to be made in this kind of study. To date, there are only a few studies about this subject, although the number is growing. The lack of research makes it harder to convince pediatricians and other physicians to recommend a therapeutic diet for their patients with autism, and parents who do have success with special diets are often dismissed as being anecdotal, one-off cases.

Jim Adams PhD of the Autism/Asperger’s Research Program at Arizona State University (ASU) has been at the forefront of studying interventions for children with autism. (We interviewed him about fecal transplants in this webinar, and you can watch the replay here.) In 2018, he and other researchers including nutritionist Julie Matthews (see our webinar interviews of her here, here and here) published the Comprehensive Nutritional and Dietary Intervention for Autism Spectrum Disorder—A Randomized, Controlled 12-Month Trial study, which showed that children with autism who ate a healthy gluten-free, casein-free, soy-free diet along with certain supplements had significantly greater improvement in autism symptoms and developmental age.

Dr. Adams was part of a team that designed a cross-sectional study, the National Survey on Treatment Effectiveness for Autism, that evaluated the effectiveness of therapeutic diets, supplements, medications, and therapies for children with autism. From this survey, Julie Matthews and Dr. Adams evaluated therapeutic diets and published their results in Ratings of the Effectiveness of 13 Therapeutic Diets for Autism Spectrum Disorder: Results of a National Survey in 2023. This study helps to answer the question: which diet is best for a child (or adult) with autism?

So Which Diet Is Best?

Before we tell you the answer, we should tell you that this study only reported the effectiveness of diets for which there were at least 20 responses. This means that some diets could be highly effective, but if there weren’t enough people participating, there’s no way to make any statistically meaningful interpretations of such limited data. Diets for which there were at least 20 responses were the following 13 diets:

• Ketogenic diet
• Corn-free diet
• Casein-free diet
• Paleo diet
• Soy-free diet
• Gluten-free diet

The Best Diet in Terms of Overall Benefit

The survey results also included diets such as the GAPS (Gut and Psychology Syndrome) diet and the low-oxalate diet, but there were not enough responses to include them in study evaluation. In addition, the Body Ecology Diet, the low-histamine diet and the low-glutamate diet – a newcomer on the scene (see our webinar interview of its developer Katie Reid PhD here), was not analyzed.

So which diet is best, overall? On a scale of 0-4 (0 = no benefit, 4 = great benefit), the answer is a healthy diet, which is defined as “a diet high in the intake of vegetables, fruit, and protein and low in junk food”. This diet had the highest net benefit (2.7) with no adverse effects. The diets with the next-best overall benefits were the Feingold diet (2.6), the food-avoidance (IgG/IgE) diet (2.6), the low-sugar diet (2.4), and the GFCF diet (2.3). However, all of the diets evaluated in the study showed significant benefit to a person with autism.

The answer to a lesser extent is: The diet that you can get your child to follow with compliance. “Positive correlations were found between how strictly diets were followed and the Overall Benefit users received from the diet.”

The Best Diet in Terms of Symptom Reduction

In terms of symptom reduction, however, the best diets were the “ketogenic diet, GFCF diet, Feingold diet, food avoidance diet based on observation, and a low sugar diet.” Because there can be some mild adverse effects associated with some of these diets, their net benefit ranked lower than a plain, old healthy diet. All of the diets evaluated in the study showed significant benefit to a person with autism.

The study showed that therapeutic diets can improve symptoms of (ranked in descending order of benefit):

• Diarrhea
• Language/communication
• Eczema/skin problems
• Stimming/perseveration/desire for sameness
• Sensory sensitivity
• Social interaction
• Understanding

When it comes to choosing the best diet for symptom reduction, it really depends which symptoms are the most pressing. For example, if your child has hyperactivity, irritability or aggression, the Feingold diet would be a good choice. Or if your child has stimming issues, the GFCF would be a logical choice.

The ketogenic diet had the highest benefit for nine symptoms: “attention (43%), cognition (37%), anxiety (33%), language/communication (29%), social interaction and understanding (29%), constipation (24%), seizures (19%), lethargy (19%), and depression (14%).” However, fewer people were following this diet, and it had the highest adverse effect (0.4) in this study. We recommend working with a knowledgeable nutritionist or doctor because it is an extreme diet.

What Happens If Symptoms Don’t Improve?

Because this study suggests that therapeutic diets are generally safe and fairly effective, it would be unusual that no symptoms improve when following any of these diets. If a diet has been followed strictly for several months and symptoms have improved but there are still remaining symptoms, we recommend looking into adding in an additional diet because there may be greater benefits when done in combination.

For example, a parent may start their child on a healthy diet and some symptoms such as constipation improved, which is a great start in improving health. However, other symptoms remain, such as hyperactivity, so the Feingold diet could be layered onto the healthy diet, and the parent removes foods containing artificial colors and flavors, preservatives, and foods with high levels of phenols and salicylates. From there, a GFCF diet could be further added in to help with attention, focus and sensory issues.

As a parent gets more well-versed in special diets and playing what Kelly Dorfman refers to as a “nutrition detective”, an elimination diet, a grain-free diet (such as the GAPS, SCD, Body Ecology Diet or paleo diet) or other special diet such as a low-glutamate, low-histamine or low-oxalate diet could be added in. Because everyone is different, different diets will have different effects, and a personalized approach works best, which is why we recommend keeping a food diary to keep track of foods eaten and any symptoms that improve or worsen over the next two to three days.

About Maria Rickert Hong CHHC

Prior to working on Wall Street, she was a marketing specialist for Halliburton in New Orleans, where she also received her MBA in Finance & Strategy from Tulane University.

She is the author of the bestselling book Almost Autism: Recovering Children from Sensory Processing Disorder and the co-author of Brain Under Attack: A Resource for Parents and Caregivers of Children with PANS, PANDAS, and Autoimmune Encephalitis. Maria is also a Certified Holistic Health Counselor. Her work can be found on EpidemicAnswers.org, DocumentingHope.com, Healing.DocumentingHope.com, Conference.DocumentingHope.com and MariaRickertHong.com

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