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Benefits of the Gaps Diet for Autism

September 29, 2023

With little more than anecdotal evidence available, should parents consider the GAPS (gut and psychology syndrome) diet for their kids on the spectrum?

If you want to divide the room, any room, start talking about your child’s diet. Elimination diets, gluten-free diets and, yes, one of the most debated: the GAPS diet.

Benefits of the Gaps Diet for Autism

But what if you could help your child thrive with some (pretty dietary adjustments? What if the most challenging autism symptoms could be treated, not with medication, but with wholesome food such as hearty broths, grass-fed beef, fermented milk products and organic vegetables? It probably sounds too good to be true… and to know for sure we’ll need the kind of research no one is lining up to fund.

The GAPS research void

When you start researching the GAPS diet, most articles will contain a caveat pertaining to the lack of research and scientific evidence needed to prove that it does indeed improve symptoms related to autism. There is quite a bit of anecdotal evidence, where parents encourage other parents with kids on the spectrum to give the diet a try. This, however, is not enough proof for parents who battle snake oil sellers at every junction of their kid’s autism journey.

A randomized controlled trial could be best to convince parents of the diet’s worth. But, in addition to funding problems, would it be practical to expect autistic children to stick to the GAPS diet for the duration of a clinical trial?

Autism and picky eating

Picky eating is a characteristic often associated with autism and attention deficit hyperactivity disorder (ADHD). It could be because of sensory processing issues that most kids on the spectrum experience to some degree; or maybe the carb heavy favorites of kids on the spectrum are because of differences in their gut microbiome (the collection of bacteria that live along the gastrointestinal tract).

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Many autism parents who submit to a daily fast food drive just to get something into their kids are not convinced they’d succeed in converting them to the restrictive GAPS diet. Converting a kid who barely tolerates a chicken nugget to chicken broth does sound like quite a feat.

From the gut

Theories about autism originating in the gut are controversial, but most parents would agree that autism affects not only their child’s brain but also their gastrointestinal system. In fact, a study (Valicenti-McDermott et al., 2006) found children with autism spectrum disorder (ASD) have a higher rate of gastrointestinal symptoms than children with other developmental disabilities and typically developing children.

But what exactly causes these differences in the gut of those on the spectrum? A recent study (Wan et al., 2021) suggests that the gut microbiota of autistic children is abnormally developed, and lags in comparison to typically developing peers. These kinds of studies are leading to a school of thought suggesting that, beyond a difference in gut microbiota, the very composition of the gut of those on the spectrum may be atypical.

Studies have found high levels of short-chain fatty acids in the stools of autistic children. Propionic acid and its related short-chain fatty acids are the fermentation products of bacteria which are often found in higher concentration in autistic individuals. Propionic acid (PPA), is also frequently used as a preservative in food, and more studies are linking it (or perhaps higher than average concentrations of it) to autism and other neurodevelopmental conditions.

PPA and gut bacteria

A meta-analysis (Iglesias-Vázquez et al., 2020) found a significantly higher abundance of Bacteroides and Clostridium in children with autism. High levels of PPA were observed in autistic children with an abundance of Bacteroides and Clostridium (Finegold et al., 2010). PPA and its associated short-chain fatty acids are the fermentation products of these ASD related bacteria (Macfabe, 2012).

When rats were treated with PPA they displayed impairments in social behavior leading the authors to conclude that PPA can change behavior in rats in a way which is consistent with characteristics of human ASD (Shultz, et al., 2008).

Recent research suggests the gut-brain axis may be a culprit in autism pathogenesis. The first study (Abdelli et al., 2019) to link “PPA and ASD-microbiome by-product to gliosis, disturbed neural architecture, and increase in inflammatory response” concludes that this may result in significant brain complications like autism.

There is a need for in-depth research to establish a link between autism and PPA, but researchers seem confident that the gut microbiome may influence symptoms and severity of autism. Bacteria is not the only gastrointestinal factor linked to autism, the gut lining may also be involved in the etiology of ASD.

Leaky gut

Researchers are interested in the implications of the atypical gut biome (of those with ASD) and its effect on the lining of the gut. More permeability of the gut or leaky gut means bacterial metabolites can cross the gut barrier—potentially neuroactive metabolites that don’t usually cross this barrier (Fowlie et al., 2018).

Studies do suggest that those on the spectrum have a higher prevalence of atypical intestinal permeability. One such study found that autistic patients who were on a gluten and casein free diet had significantly lower intestinal permeability values than patients on an unrestricted diet (de Magistris et al., 2010).

There are other studies with conflicting evidence and some researchers are simply not convinced that the gut plays a major role in ASD. But parents dealing with their children’s gastrointestinal issues on a daily basis may find the scientific reasoning linking ASD and gut health interesting. A parent who’s witnessed an increase of challenging symptoms after consumption of specific food may be especially interested in how a dietary overhaul may influence their child’s neurodevelopmental condition.

Does research pertaining to possible differences in the autistic child’s gut mean it’s time to rethink your child’s entire diet and adopt a strict regimen? Proponents of the GAPS diet seem to think so.

The doctor behind the diet

Dr. Natasha Campbell-McBride designed the GAPS diet, a natural approach to help treat behavioral and mood disorders. She coined the term Gut and Psychology Syndrome (GAP Syndrome or GAPS) which is described on her website as: “a condition establishing a connection between the functions of the digestive system and the brain.”

Dr. Campbell-McBride, a medical doctor with postgraduate degrees in nutrition and neurology, designed the diet as her own son had a learning disability. She believes a leaky gut and poor nutrition is involved in many neurological and behavioral conditions.

It’s easy to imagine how a gut with an abundance of ASD-associated bacteria and a leaky intestines may affect the rest of the body and brain. The obvious solution must be to solve the gut problems so the brain is not negatively influenced by toxins that were never supposed to cross the gut barrier. The GAPS diet was designed to heal digestion naturally. The diet promotes a healthy immune system which requires a healthy gut microbiome.

The diet reduces inflammation, it may help restore a leaky gut, and it encourages a diverse and healthy gut microbiome—at least that’s some of the claims made by those who swear by it.

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What is the GAPS diet?

The protocol

The GAPS diet website mentions the protocol consists of three parts and it was created to:

  1. Help with healing and sealing of the gut lining
  2. Restoration of the ecosystem of bacteria in the gastrointestinal tract
  3. Restore balance of the immune system

The website also mentions that the protocol consists of three parts: Diet, supplementation, and detoxification.


This is probably the most intriguing and complicated part of the protocol. No grains, processed carbohydrates, and refined sugar are permitted. Commercial dairy is out too, but it seems hard cheese and milk products fermented at home for longer than 24 hours is allowed. Starchy vegetables are not allowed either, and there is a warning to go slow on fruit and baked goods (which are only permitted when made with nut and seed flours).

The protocol encourages a diet rich in nutrient dense food that is easily digestible. The following are some of the foods allowed on the gaps diet, (depending on the relevant stage/phase):

  • Homemade meat stocks
  • Bone broth
  • Fermented food and drinks
  • Organic venison, beef, chicken, pork, duck, and turkey
  • Specific types of fish and fresh shellfish
  • Organic eggs
  • Organic vegetables, and (limited) fruit
  • Nuts and seeds

The diet starts off with severe restrictions at stage one of the introduction phase. As the individual progresses through the various stages and moves on to the “full GAPS diet” more food types are added. The diet is not meant to be followed permanently; rather it is a therapeutic diet which is typically followed for about two years until digestion or digestive issues are healed.

The GAPS diet is a detailed protocol, to achieve healing an individual should follow all the stages and phases. The first stage for example, is all about reducing gastrointestinal symptoms like diarrhea and bloating. During this initial stage foods like: homemade chicken stock, vegetable based probiotic food, and ginger tea to soothe an inflamed, angry gut are encouraged.

With each progressive stage more foods are added, these are all grain-free, nutrient dense choices with an emphasis on fermented foods. After stage six the individual is ready to embark on the full GAPS diet.

A person suffering from severe constipation, poor fat digestion, histamine issues and various other complications, may need a tailored version of the GAPS diet. There are also many detailed instructions concerning the intake of dairy; lactose should be avoided— therefore dairy is fermented at home.The devil is in the details (or in this case the diet) and that is why reading the book is recommended before starting out.

For parents with extremely picky eaters the idea of a diet based on soup, fermented food and organic vegetables may serve as enough of a scare to quit before trying. No bread, no nuggets, no fish sticks? Perhaps these parents will find it encouraging to note that some children put up a ferocious fight only to accept the protocol once they start feeling better. Or as some believe, when the craving for starchy, sugary foods disappears as the bad bacteria responsible for the cravings are eliminated.

The diet is divided in two parts or phases: the introduction diet and the full GAPS diet. There is even mention of an additional stage to provide guidance when coming off the GAPS diet. The introduction diet is divided in six stages and it can take anywhere from three to six weeks to complete (some people complete it in as little as two weeks). After completing all six stages the individual moves on to the full GAPS diet—which needs to be followed for around two years.

The website gives more details but should only be used as a complement to Dr. Campbell-McBride’s book (Gut And Psychology Syndrome. Natural Treatment Of Autism, ADHD, Dyslexia, Dyspraxia, Depression And Schizophrenia) which contains all relevant information needed to embark on the diet.


This part of the protocol may need input from a doctor or therapist to help identify the additional support required, every individual’s needs and deficiencies are unique and supplementation will need to be adjusted accordingly. Probiotics play a major part in healing, and for this reason the GAPS diet specifies therapeutic strength probiotics. Other supplements like fatty acids, vitamins, minerals, and digestive enzymes may be needed to support healing of the digestive system.


The protocol may even require you to chuck out some of your cleaning products, cosmetics and any other chemicals in your home. The aim is to reduce the toxic load in your home environment.

Does it work?

Many testimonials are positive and promise all the sacrifice and difficulty are worth it as the most challenging symptoms of autism become less pronounced, and sometimes disappear. Reading about the diet and the experience of parents who embark on it with their kids makes it abundantly clear that the GAPS diet is not a quick fix—it does require substantial effort, planning and adjustment from the entire family.

For parents worried about their child’s cravings and behavior due to deprivation of “comfort foods” there may be hope after a few weeks on the diet. Parents speak of cravings disappearing once some of the abundance of ASD-associated bacteria is reduced. They also mention how much calmer their children and their entire home becomes. Parents who convert to the GAPS way of eating for their kids sake, share how their allergies, sinus infections, and other ailments disappear.

Cost may be a worry for parents thinking about adopting the diet. As no grains are allowed, baking requires nut or seed flour which may be more expensive than wheat and maize flour. The advice seems to be to stick to soups, roast meats and organic veg as staples, these are affordable and nutrient dense choices. Many mothers say the cost of the diet is offset by how much less medical intervention their children require as their gut starts healing.

Video testimonials like the one I found on a website called Cheese Slave (and the comments provided by other families) are the kind of encouragement parents crave to take the dive. As encouraging as the results are, there is unfortunately no way to verify such progress scientifically. Because autism is a spectrum condition, with heterogeneous symptoms presented by each individual, the success or improvement of the GAPS diet will depend on the individual, and their unique digestive and behavioral issues.

Consult your doctor and dietician

It is important to note that there are medical professionals who view the GAPS diet negatively. The lack of scientific proof, the restrictiveness, lack of fibre due to elimination of all grains, and the long term duration of the diet are some of their most pressing concerns.

A very restrictive diet may lead to deficiencies especially in growing children. Parents who feel the GAPS diet may help their autistic child thrive should proceed with caution. Getting the help of a nutritionist to ensure your child is getting optimum nutrition could be helpful, and necessary, as the diet does eliminate many food types. Consult your child’s doctor, especially if he or she has ever identified deficiencies and allergies in your child. A doctor familiar with your child’s medical history will provide appropriate medical guidance concerning your child’s unique nutritional needs.

Parents who are still on the fence should research the diet and reach out to parents whose kids have tried it. Not only the kids who thrived on the diet, also kids who quit and those who saw little difference. Parental instinct, a lot of research and the expert opinion of therapists and your child’s doctor should help you decide if the GAPS diet could be helpful for your child on the spectrum.

Most importantly the diet should be approached as something with potential to help your child thrive, not to “cure” them. Autism is a spectrum condition and as your child grows their symptoms may change and their needs will evolve. Ensuring they receive the best nutrition, supplementation and necessary dietary adjustments will help them become the best version of themselves.


Abdelli, Latifa & Samsam, Aseela & Naser, Saleh. (2019). Propionic Acid Induces Gliosis and Neuro-inflammation through Modulation of PTEN/AKT Pathway in Autism Spectrum Disorder. Scientific Reports. 9. 10.1038/s41598-019-45348-z.

de Magistris, L., Familiari, V., Pascotto, A., Sapone, A., Frolli, A., Iardino, P., Carteni, M., De Rosa, M., Francavilla, R., Riegler, G., Militerni, R., & Bravaccio, C. (2010). Alterations of the intestinal barrier in patients with autism spectrum disorders and in their first-degree relatives. Journal of pediatric gastroenterology and nutrition, 51(4), 418–424. https://doi.org/10.1097/MPG.0b013e3181dcc4a5.

Finegold, S. M., Dowd, S. E., Gontcharova, V., Liu, C., Henley, K. E., Wolcott, R. D., Youn, E., Summanen, P. H., Granpeesheh, D., Dixon, D., Liu, M., Molitoris, D. R., & Green, J. A., 3rd (2010). Pyrosequencing study of fecal microflora of autistic and control children. Anaerobe, 16(4), 444–453. https://doi.org/10.1016/j.anaerobe.2010.06.008.

Fowlie, G., Cohen, N., & Ming, X. (2018). The Perturbance of Microbiome and Gut-Brain Axis in Autism Spectrum Disorders. International journal of molecular sciences, 19(8), 2251. https://doi.org/10.3390/ijms19082251

Iglesias-Vázquez, L., Van Ginkel Riba, G., Arija, V., & Canals, J. (2020). Composition of Gut Microbiota in Children with Autism Spectrum Disorder: A Systematic Review and Meta-Analysis. Nutrients, 12(3), 792. https://doi.org/10.3390/nu12030792.

Macfabe D. F. (2012). Short-chain fatty acid fermentation products of the gut microbiome: implications in autism spectrum disorders. Microbial ecology in health and disease, 23, 10.3402/mehd.v23i0.19260. https://doi.org/10.3402/mehd.v23i0.19260.

Shultz, S. R., MacFabe, D. F., Ossenkopp, K. P., Scratch, S., Whelan, J., Taylor, R., & Cain, D. P. (2008). Intracerebroventricular injection of propionic acid, an enteric bacterial metabolic end-product, impairs social behavior in the rat: implications for an animal model of autism. Neuropharmacology, 54(6), 901–911. https://doi.org/10.1016/j.neuropharm.2008.01.013.

Valicenti-McDermott, M., McVicar, K., Rapin, I., Wershil, B. K., Cohen, H., & Shinnar, S. (2006). Frequency of gastrointestinal symptoms in children with autistic spectrum disorders and association with family history of autoimmune disease. Journal of developmental and behavioral pediatrics : JDBP, 27(2 Suppl), S128–S136. https://doi.org/10.1097/00004703-200604002-00011.

Wan, Y., Zuo, T., Xu, Z., Zhang, F., Zhan, H., Chan, D., Leung, T. F., Yeoh, Y. K., Chan, F., Chan, R., & Ng, S. C. (2021). Underdevelopment of the gut microbiota and bacteria species as non-invasive markers of prediction in children with autism spectrum disorder. Gut, gutjnl-2020-324015. Advance online publication. https://doi.org/10.1136/gutjnl-2020-324015.

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