Kelly Barnhill, MBA, CN, CCN, discusses nutrition in autism based on recent publications. She outlines research updates on amino acid patterns, probiotics, and dietary interventions, underscoring both what we know and what we don’t know. The speaker discusses the clinical interpretation and application of this research, touching on common nutrient deficiencies before the Q&A.

In this webinar:

0:00 – Introductions
2:00 – Prospective study on amino acid patterns
5:50 – Prospective Study on Probiotic Intervention
7:40 – Systematic Review of Dietary Intervention and Gut Health
10:54 – Bibliometric Analysis of Influential Articles
13:47 – Systematic Review of Probiotics in Autism
16:06 – Nutrition Reviews Study on Mediterranean Diet
19:28 – Study on Gluten- and Casein- Free Diet
21:48 – Review on Ketogenic Diet
26:16 – Food, Nutrition, and Autism
27:57 – Systematic Review – Food as Medicine
34:40 – Clinical interpretation and application
40:30 – Micronutrients
44:10 – Q&A

Prospective Study on Amino Acid Patterns 

Dr. Barnhill outlines a 2025 study on amino acid patterns in over 1,200 children (2-8 years) with autism. Researchers found lower levels of glutamine in children with autism and significant differences in several amino acids across groups (2:00). Specifically, the study noted that those with neurological impairment were deficient in amino acids that presented with susceptibility to neurocytotoxicity and oxidative stress, while those with nutritional concerns presented with a different set of issues, pointing more toward metabolic concerns. Barnhill explains that these findings substantiate clinical observations and suggest that specific amino acid imbalances may be related to different manifestations of autism, supporting the use of nutritional therapeutic intervention to balance amino acid levels. The speaker emphasizes that this is the only amino acid study presented in a prospective way that has been published in a reputable journal in the past few years. 

Amino Acid Patterns in Children with Autistic Spectrum Disorder: A Preliminary Biochemical Evaluation (Ferraro et al., 2025)

Prospective Study on Probiotic Intervention 

The presenter outlines another recent study that speaks to the concerns of effects of probiotic support for children with autism, AD/HD, and children with both diagnoses (AuDHD) (5:50). Children were given a probiotic or a placebo for three months. Researchers saw a significant improvement in hyperactivity and impulsivity in both the autism and ADHD groups. Most notably, the “comfort score” on a quality-of-life instrument showed significant improvement for autistic children. Barnhill notes that, although this is a small study, its findings support clinical observations that probiotics can improve gastrointestinal symptoms and other related issues in children with autism, potentially impacting their quality of life.

Effect of Probiotics on the Symptomatology of Autism Spectrum Disorder and/or Attention Deficit/Hyperactivity Disorder in Children and Adolescents: Pilot Study (Rojo-Marticella et al., 2025)

Systematic Review of Dietary Intervention and Gut Health 

Barnhill examines a systematic narrative review of all articles published between 2000 and 2024 related to autism, dietary interventions, probiotics, and the microbiome. (25-year review) (7:40). The review validated that dietary intervention can improve GI symptoms and gut health for children with autism, which in turn improves their quality of life. Researchers also identified a cycle where sensory processing issues lead to food avoidance (ARFID), which decreases microbiome diversity and increases harmful microbial species, leading to a neuroinflammatory process that affects behavior (9:12). The speaker asserts that this review provides a strong rationale for addressing GI and microbiome concerns as part of a comprehensive care plan for individuals with autism.

Unraveling the Connections: Eating Issues, Microbiome, and Gastrointestinal Symptoms in Autism Spectrum Disorder (Tomaszek et al., 2025)

Bibliometric Analysis of Influential Articles 

The speaker highlights another 25-year study that reviewed all publications on microbiome treatment in autism since 2000 to identify the most impactful and cited articles (10:54). This is one of the first in a series of bibliometric analyses. The study identified two landmark publications: a 2013 mouse model study that established the link between the gut microbiome and ASD, and a very early, relatively small study from 25 years ago that showed improvements in both GI symptoms and behavior in a small group of autistic children treated with an oral antibiotic. These two studies, along with many more, laid the groundwork for the growing field of gut-brain research in autism and further validated the clinical utility of targeting gut health.

Influential articles in autism and gut microbiota: bibliometric profile and research trends (Ying et al., 2025)

Systematic Review of Probiotics in Autism 

Barnhill discusses a systematic review that analyzed 10 completed and published clinical studies, as well as 18 ongoing clinical trials, on the use of probiotics in autism. (13:47). Reviewers found that probiotics can improve social behaviors, drastically improve GI symptoms, and positively alter the gut microbiome when used appropriately. The presenter emphasizes this paper as a valuable and easily accessible resource for clinicians and parents, as it provides research backing for the use of probiotics in addressing a range of symptoms beyond just GI issues – essentially describing what we’ve learned and why it’s important.

Probiotics in autism spectrum disorders: a systematic review of clinical studies and future directions  (Barba-Vila et al., 2025)

Nutrition Reviews Study on Mediterranean Diet

Barnhill notes that we are seeing more and more solid research emerging about how dietary intervention benefits individuals across the board, highlighting that there is no one-size-fits-all approach for any of us and what that means for clinical applications. She outlines a 2025 evaluation of all studies on children (6-16 years) with autism and ADHD, examining responses to nutritional interventions (16:06). The paper concluded that 70% of individuals who followed a Mediterranean diet showed significant improvement in ADHD symptoms. It also noted significant improvements in depression (80%) and anxiety (50%). The speaker states that these results suggest that focusing on a whole, unprocessed Mediterranean-style diet can be a profound and effective intervention for improving neurological and mental health symptoms. 

Mediterranean Diet and Mental Health in Children and Adolescents: A Systematic Review (Camprodon-Boadas et al., 2025)

Study on Gluten- and Casein-Free Diet

The speaker outlines another 2025 study that evaluated a 12-week trial involving 80 children (4-10 years), using a strict, prescribed gluten- and casein-free diet in combination with and separate and distinct from a neurodevelopmental physical therapy program (19:28). Barnhill notes that families prepared meals on their own, meaning there was no technical control group. Researchers saw significant gains in gross motor skills and cognitive function only when the diet was combined with the therapy program. The dietary group alone showed no significant changes. This study suggests that a multidisciplinary, holistic approach is key, and that dietary interventions may be more effective when combined with other therapies.

Effect of Therapeutic Diet Along with Special Physiotherapy Program on Gross Motor Development and Cognitive Function in Autistic Children: A Randomized Controlled Trial (Alsayegh et al., 2025)

Review on Ketogenic Diet

A review of all published papers on the ketogenic diet for individuals with autism found that the diet is not appropriate for everyone due to the high heterogeneity of autism. However, Barnhill continues, it does hold great potential for some individuals by reducing bacterial dysbiosis, decreasing pro-inflammatory cytokines, enhancing gut health, and providing a neuroprotective effect via ketone bodies (21:48). Barnhill underscores that while the ketogenic diet can be effective for the right patient, it should only be implemented with professional guidance due to its complexity and potential dangers when applied inappropriately. More research is needed.

Exploring the potential of the ketogenic diet in autism spectrum disorder: metabolic, genetic, and therapeutic insights (Schrickel et al., 2025)

Food, Nutrition, and Autism

The presenter provides a summary article describing our current understanding of nutrition and autism from a societal and cultural perspective. The paper tangentially addresses all the issues that people in the US should be aware of and attuned to, including environmental and food exposures from prenatal to childhood. Barnhill asserts this study is foundational for building an appropriate dietary approach and understanding what barriers might exist (26:16). 

Food, nutrition, and autism: from soil to fork (Shepard et al., 2024) 

Systematic Review – Food as Medicine

The speaker notes a recent systematic review that addresses the use of dietary intervention and therapeutic nutritional support across various diagnoses (27:57). The authors highlight several publications that support the idea that food can be considered a form of medicine and is increasingly understood as a pharmaceutical component in health and medical diagnoses. Barnhill emphasizes the importance of not viewing food choices and dietary recommendations for autism as “other” to the general population’s nutritional understanding. Culturally, we continue to recognize that our diets are integral to health and need to be taken seriously. She states that “we need to hold autism research and interventions to the same standards.” This study ultimately resolidifies the interconnectedness of the gut and brain by highlighting the impact of microbiome health in the GI system on both the vagal nerve and cognition (31:00). 

Nutraceuticals in Psychiatric Disorders: A Systematic Review (Bozzatello et al., 2024)

Clinical interpretation and application

According to the presented information, Barnhill asserts that clinicians should assume that diet matters and that a nutritionist or dietary specialist should be included in care counseling and planning for children and adults with autism (34:40). She underscores the importance of avoiding packaged food products, ensuring fiber and water intake are sufficient, and addressing feeding concerns with care and compassion. She also suggests incorporating family and community into diet changes, meal preparation, and eating habits. The speaker also suggests working with a professional to outline any specialized diets (37:40). 

Micronutrients & Therapeutic Support

Barnhill lists common micronutrient deficiencies, including B vitamins, fat-soluble A and D, and Omega-3 fatty acids. She notes that addressing gaps with supplemental support is reasonable and appropriate to meet the minimal needs in the case that someone doesn’t have access to those nutrients via diet (40:30). She cautions viewers about the supplement market, noting that it is not regulated; and suggests consulting with someone well-versed in what’s needed and the efficacy of different brands before the Q&A (44:10). 

Francesca Solmi, Ph.D., discusses the intricate link between autism and eating disorders. She outlines common eating disorders, noting their overlapping symptoms and similarities to autism traits. The speaker explores potential mechanisms for the connection between eating disorders and autism, including communication difficulties, sensory sensitivities, and emotion regulation. Solmi emphasizes Avoidant/Restrictive Food Intake Disorder (ARFID) and its relevance to autism, underscoring the need for more research and services for this often overlooked condition. The presenter considers future research directions before the Q&A.  

Handouts are online HERE

In this webinar:

1:30 – Common eating disorders
8:00 – Autism and eating disorders
11:00 – Trajectories of autistic traits and eating disorders
20:00 – Potential linking mechanisms
28:00 – Emotion regulation
34:50 – Avoidant/Restrictive Food Intake Disorder (ARFID) and Autism
40:00 – Future research
42:00 – Q&A

Overview of Eating Disorders 

Solmi defines eating disorders as severe psychiatric conditions that typically emerge in early to mid-adolescence. She describes common eating conditions, including Anorexia Nervosa, Bulimia Nervosa, Binge Eating Disorder, and OSFED (Other Specified Feeding or Eating Disorder), highlighting the significant symptom overlaps across conditions (1:35).

• Anorexia Nervosa – frequently the youngest age of onset. Characterized by an intense fear of weight gain, extreme dietary restriction, and often low body weight. Some individuals may also engage in bingeing and purging.
• Bulimia Nervosa – slightly later onset and involves episodes of binging followed by compensatory behaviors like self-induced vomiting or excessive exercise.
• Binge Eating Disorder – the most recently recognized diagnosis. It involves bingeing without compensatory behaviors, often accompanied by feelings of shame or guilt.
• OSFED (Other Specified Feeding and Eating Disorder) is a residual category for individuals whose symptoms don’t fully meet the criteria for other diagnoses. 

The speaker emphasizes the severity of these conditions, noting their association with higher mortality rates (5:00). Despite this, eating disorders are often under-researched compared to other mental health disorders. She also notes their high prevalence in girls and women, suggesting underdiagnosis in men (6:30).  

The Link Between Autism and Eating Disorders 

Solmi discusses the connection between autism and eating disorders. A study by Westwood and colleagues revealed elevated autistic traits in people with anorexia nervosa. Similarly, people with autism and anorexia nervosa mentioned rigidity or rules, intense interests, difficulties recognizing hunger, and social difficulties (8:00). A significant challenge in this research, the presenter explains, is distinguishing between pre-existing autistic traits and those that may be mimicked by severe malnutrition in anorexia nervosa. 

Autism Spectrum Disorder in Anorexia Nervosa: An Updated Literature Review (Westwood et al., 2016)

Research on Autistic Traits and Disordered Eating Trajectories

Solmi presents findings from a study investigating whether autistic traits were present before the onset of disordered eating behaviors (11:00). Researchers found that children who later developed disordered eating behaviors exhibited higher levels of autistic traits at age seven, and these differences persisted throughout adolescence. The speaker asserts that these findings suggest autistic traits may precede the onset of disordered eating (17:00). The study also revealed that more severe eating disorder symptoms correlated with higher autistic trait scores from age seven onwards, indicating a strong association with more severe presentations of eating disorders.

Trajectories of autistic social traits in childhood and adolescence and disordered eating behaviours at age 14 years: A UK general population cohort study (Solmi et al., 2020)

Potential Mechanisms Linking Autism and Eating Disorders 

The presenter explores several mechanisms as potential links between autism and eating disorders. For example, as friendships become more important in adolescence, struggles with social interaction can exacerbate mental health difficulties, with eating disorders potentially serving as a coping mechanism. Children with social communication difficulties may also be more susceptible to bullying, which can lead to internalized weight-stigmatizing thoughts and behaviors like dieting (20:00). Young people with autism often exhibit more sedentary behaviors compared to their peers, which can increase BMI and vulnerability to weight-based stigmas (23:00). 

Emotion regulation difficulties are also common in both autism and eating disorders. Solmi outlines a recent study showing that individuals who later developed anorexia nervosa symptoms exhibited less improvement in emotion regulation skills from early to mid-childhood compared to their peers, where differences emerged around age five (30:00). Further, in girls, social cognition explained around half of the association between emotion regulation difficulties and disordered eating. The association in boys was less clear, likely due to smaller sample sizes (35:00).

The presenter notes that sensory sensitivities, a core aspect of avoidant/restrictive food intake disorder (ARFID), are frequently reported by people with anorexia nervosa. For example, in a qualitative study on autism and anorexia in women, emerging themes included difficulty with sensory sensitivities, social interactions and relationships, and challenges with emotions (33:00). 

A mixed-methods approach to conceptualizing friendships in anorexia nervosa (Datta et al., 2021)

Autism Spectrum Disorder and Obesity in Children: A Systematic Review and Meta-Analysis (Sammels et al., 2022)

Emotional dysregulation in childhood and disordered eating and self-harm in adolescence: prospective associations and mediating pathways (Warne et al., 2022)

“For Me, the Anorexia is Just a Symptom, and the Cause is the Autism”: Investigating Restrictive Eating Disorders in Autistic Women (Brede et al., 2020)

Avoidant/Restrictive Food Intake Disorder (ARFID) and Autism

Solmi discusses ARFID, a disorder now included in the eating and feeding disorder family, noting its relevance to autism. Its three main aspects include limited interest in food, sensory sensitivities (e.g., avoiding specific foods due to texture), and concerns about adverse consequences from eating (34:50). The speaker emphasizes the limited epidemiological research on ARFID, the lack of services (especially for people who are not severely underweight), and the need for more studies to understand its prevalence, risk factors, and effective treatments (37:00).

Future Research Directions 

According to the presenter, future research should aim to understand the complex links between autism and eating disorders more comprehensively. Key areas of investigation include the connections between sensory sensitivities and ARFID, gender differences in the association of autistic traits and eating disorders, links between other autistic traits and different eating disorder presentations, physiological factors like the gut-brain response, and age of autism diagnosis in those with and without eating disorders. These avenues of research, Solmi asserts, will improve diagnostic tools and help to develop better prevention and care strategies (40:00). The speaker summarizes main points before the Q&A (42:20). 

Mojdeh Mostafavi, MD, describes gastrointestinal conditions commonly seen in individuals with autism, including gastroesophageal reflux disease (GERD), inflammatory bowel disease (IBD), Eosinophilic GI disease (EGID), avoidant/restrictive food intake disorder (ARFID), disorders of the gut-brain interaction (DGBI), and constipation. She outlines recent research on the prevalence of these conditions in people with autism, emphasizing the complexities of symptom presentation, drivers, and care. The speaker provides a free social story for endoscopies and considers the relationship between pain expression and GI conditions. Mostafavi discusses the difficulties of transitioning from pediatric to adult healthcare in autism. She summarizes the presentation before the Q&A.

Handouts are available HERE

Recommendations for evaluation and treatment of common gastrointestinal problems in children with ASDs – PubMed (article discussed during the talk)
Understanding and Treating Self-Injury Book (book mentioned during the talk)

In this webinar:

1:10 – Introduction, disclosures, language preferences
2:35 – Autism and gastrointestinal conditions
10:20 – Gastroesophageal Reflux Disease (GERD)
14:10 – Inflammatory bowel disease
18:00 – Eosinophilic GI disease (EGID)
22:10 – Avoidant/restrictive food intake disorder (ARFID)
27:15 – Disorders of the gut brain interaction (DGBI)
33:00 – ASD and constipation
37:00 – Resources and tips
46:20 – Conclusion
48:00 – Q&A

Autism and GI conditions

Mostafavi defines autism and lists common co-occurring conditions, including seizures, psychiatric disorders, and gastrointestinal (GI) conditions (2:35). She notes that between ~40% – 70% of children with autism have GI symptoms with a significantly higher lifetime prevalence and that measurement tools don’t capture all GI symptoms (5:30). The most common GI complaints reported by autistic people are constipation, abdominal pain, feeding difficulties, encopresis, and weight loss/failure to thrive (8:40). The speaker underscores the importance of defining these conditions in autism and discusses some of the most common co-occurring GI conditions. 

• The Prevalence of Gastrointestinal Problems in Children Across the United States With Autism Spectrum Disorders From Families With Multiple Affected Members (Wang et al., 2011)
• Gastrointestinal Symptoms in Autism Spectrum Disorder: A Meta-analysis (McElhanon, 2014)
• Gastrointestinal Symptoms in Children with an Autism Spectrum Disorder and Language Regression (Valicenti-McDermott et al., 2008)
• Characterization of Initial Gastrointestinal Evaluation of Children with Autism Spectrum Disorder: A Descriptive Study (Mostafavi et al., 2024)

Gastroesophageal Reflux Disease (GERD)

Gastroesophageal Reflux Disease (GERD) occurs when stomach acid refluxes into the esophagus. This is one of the better-understood GI conditions in autism. Mostafavi outlines a recent study that found that people with autism have a higher risk of developing erosive esophagitis and esophageal ulcers compared to non-autistic groups (10:20). She remarks that acid-blocking medications can mitigate some risk and describes the BRAVO wireless and nasal probe tests for GERD (10:20). 

• Evaluation of Gastroesophageal Reflux Disease in Children on the Autism Spectrum: A Study Evaluating the Tolerance and Utility of the BRAVO Wireless pH Monitoring (Rodriguez et al., 2022)

Inflammatory bowel disease

Inflammatory bowel disease (IBD) is broadly characterized by Crohn’s disease and ulcerative colitis, which are caused by inflammation of the GI tract. A recent systematic review and meta-analysis (6 studies, 11 million participants) found an association between autism and the later development of IBD. Mostafavi notes that children with autism often have more potent treatments (second-tier biologics) for GI conditions compared to non-autistic children with GI issues, underscoring their severity in autism (14:10). 

• Association of Autism Spectrum Disorders and Inflammatory Bowel Disease (Lee et al., 2018)

Eosinophilic GI disease (EGID)

Eosinophilic GI disease (EGID) looks at the entire GI tract and is associated with an imbalance in the immune system potentially related to food sensitivities. Over time, complications can include fibrosis and eosinophilic esophagitis (EOE). The speaker outlines a recent systematic review and meta-analysis (6 studies, +700,000 participants), which revealed an association between autism and EGID, where the prevalence of autism in the EGID population is 21.59% (18:00). 

Avoidant/restrictive food intake disorder (ARFID) 

Avoidant/restrictive food intake disorder (ARFID) is related to at least one of the following:

• Fear of consequences (symptoms that the food triggers)
• Sensory aversion
• Lack of interest/awareness of appetite cues 

Unlike other eating disorders, ARFID is not related to body appearance. Mostafavi notes inadequate caloric intake and deficiencies in micronutrients and vitamins as concerns associated with ARFID. Recent research shows a significant relationship between autism and ARFID, and sensory issues are the most commonly described driver (22:10). The presenter suggests trying treatments like oral desensitization and pairing foods and asserts that applying what works in other intervention spheres to ARFID may be possible (25:20). 

• The Co-Occurrence of Autism and Avoidant/Restrictive Food Intake Disorder (ARFID): A Prevalence-Based Meta-Analysis (Sader et al., 2024)
• Avoidant/restrictive food intake disorder and severe food selectivity in children and young people with autism: A scoping review (Bourne et al., 2021)

Disorders of the gut brain interaction (DGBI)

The gut-brain access involves both nervous systems; many neurotransmitters are produced in our guts. Mostagavi asserts that just because labs come back negative does not mean that GI symptoms are not real because there is no specific test for DGBI (27:15). A retrospective study found that nearly one-third of participants seen through an autism-specific clinic experienced functional GI conditions. The speaker underscores how difficult pain localization can be for people with autism due to complications with interoception (31:00). 

• Functional Gastrointestinal Disease in Autism Spectrum Disorder: A Retrospective Descriptive Study in a Clinical Sample (Penzol et al., 2019)
• Characterization of Initial Gastrointestinal Evaluation of Children with Autism Spectrum Disorder: A Descriptive Study (Mostafavi et al., 2024)

Autism and constipation

Constipation is one of the most reported GI symptoms associated with autism. However, chronic constipation does not seem to be associated with a higher rate of abnormal colonic motility in autism. Mostafavi outlines research showing that children with autism are more likely to visit the ER and be admitted to the hospital for constipation-related issues compared to children with other or no chronic conditions. This significantly increases healthcare costs and utilization, increasing the chances of poor quality or lack of treatment (33:00). 

• Evaluation of Chronic Constipation in Children With Autism Spectrum Disorder (Coe et al., 2023)

Resources and tips

The presenter notes a 2010 article published in Pediatrics as a good reference for GI issues in autism. The article talks about constipation, guidelines for evaluation in patients with high-risk, mitochondrial conditions, and medication (37:00). Mostafavi suggests using a joint provider who can obtain information on health history, blood and stool work, imaging studies, etc., to compile a complete picture of drivers and symptoms (38:15). Endoscopies can be particularly helpful in assessing GI disturbances in autism and Mostafavi provides a free endoscopy social story available in English, Spanish, Brazilian Portuguese, Arabic, and Haitian Creole (40:00). 

Access Google Drive with social story documents – https://bit.ly/endoscopysocialstory

The speaker highlights that many behavior issues in autism are associated with pain, like irritability, oppositional behavior, meltdowns, and more. She notes the Understanding and Treating Challenging Behaviors in Autism book and how it describes causes of aggression and self-injurious behavior (SIB) in autism as having both physiological and social/behavioral causes. She lists pain behaviors that are often misinterpreted, highlighting that people can demonstrate one or many forms of behavior across different contexts (41:55). Mostafavi touches on the transition from pediatric to adult care and how difficult it can be for autistic people to acquire the necessary care and support (44:00). 

Summary

The speaker summarizes the presentation, highlighting that the majority of people with autism have associated GI-related symptoms or conditions, the most common of which are DCBI, GERD, IBD, EGID, and ARFID. She emphasizes the importance of comprehensive evaluation with guidance from a gastroenterologist where necessary. Mostafavi reminds viewers that children with autism become autistic adults with similar care needs (46:20). She notes the ongoing complexities of discourse around the association between GI issues and autism before the Q&A (48:00). 

Originally published on March 4, 2025.

Dr. Bradley Ferguson, PhD, a 2024 research grant recipient, discusses emerging research on the interaction of GI symptoms and stress in autism. He outlines recent investigations highlighting the connection between GI issues, cortisol levels, and internal and external behaviors. The speaker discusses electrodermal activity (sweat) as a way to measure and predict problem behaviors and considers the potential for treating stress to alleviate GI symptoms. Ferguson underscores the importance of real-world data and outlines ongoing work funded by ARI, which uses smartwatches to monitor physical and social indicators of stress behavior over three weeks. He describes current hypotheses and potential implications for this work before the Q&A.

In this webinar:

1:30 – Stress and the gut
6:30 – Stress and communication
13:13 – Electrodermal activity
17:20 – Treating the stress response
25:30 – Ongoing work
31:47 – “CORE Autism” smartwatch app
37:45 – Implications
39:35 – Summary
42:00 – Q&A

The gut and stress

The prevalence of co-occurring gastrointestinal (GI) issues in autism ranges from 9 to 91%, with constipation being the most common (1:30). Research shows that many autistic people have a heightened stress response which activates the sympathetic nervous system – fight or flight mode – and inhibits stomach function. Ferguson and his team look at GI issues through a stress lens, suggesting that activation of the sympathetic nervous system is related to a lot of GI issues (3:00). He outlines past work that shows a positive relationship between levels of cortisol, a stress marker, and constipation (4:30). Similar work shows that having co-occurring anxiety significantly altered parasympathetic nervous system activity in the lower GI tract, meaning that anxiety is related to GI symptoms in autism (5:40). 

In a 2019 study, Ferguson and colleagues used caregiver questionnaires for 340 autistic children and adolescents to assess correlations between GI conditions and behavior issues (6:30). Results showed that across all ages, 65% experienced constipation, 50% experienced stomach aches, 29% experienced diarrhea, and 23% experienced nausea, where 53% were taking medications for other conditions (ADHD, seizures), and 93% were not taking any GI meds (9:30). In children between the ages of 1 and 5, nausea significantly predicted aggression. Ferguson says that this correlation is likely to do with the children’s inability to communicate their nausea, which leads them to act out. In participants between 6 and 18 years old, anxiety, withdrawn behavior, and somatic complaints were 11% more likely to experience aggression, stomachaches, and nausea, respectively, and less likely to experience certain other GI symptoms (10:55).

The speaker summarizes research findings to date, highlighting that non-verbal young children may use aggression to communicate somatic complaints and that older children have more internalizing behaviors associated with GI symptoms. 

Associations between cytokines, endocrine stress response, and gastrointestinal symptoms in autism spectrum disorder (Ferguson et al., 2016)

Psychophysiological Associations with Gastrointestinal Symptomatology in Autism Spectrum Disorder (Ferguson et al., 2016)

The Relationship Among Gastrointestinal Symptoms, Problem Behaviors, and Internalizing Symptoms in Children and Adolescents With Autism Spectrum Disorder (Ferguson et al., 2019)

Electrodermal activity and problem behavior

Electrodermal activity, or skin sweat, is part of the stress response triggered by the sympathetic nervous system. Using a smartwatch, researchers were able to track skin conductance (sweat) from baseline to post-behavior levels (13:13). Results showed a rise in sweat about 60% of the time prior to a problem behavior occurring and a return to baseline afterward about 45% of the time. The average rise in skin conductance before a behavior was around 10 minutes (15:15). 

Examining the Association Between Electrodermal Activity and Problem Behavior in Severe Autism Spectrum Disorder: A Feasibility Study (Ferguson et al., 2019)

Treating the stress response

Ferguson and his team assessed a trial of propranolol, a beta blocker (blocks stress response), in children and youth with autism. Results showed a significant reduction in anxiety for the propranolol group compared to controls (17:20). He outlines an fMRI study on the relationship between GI issues and amygdalar activity. The study revealed that participants taking propranolol (which crosses the blood-brain barrier) showed a neutral relationship between GI symptoms and amygdala activity. In contrast, those taking nadolol (which does not cross the blood-brain barrier) or a placebo showed a positive correlation. Ferguson explains that these findings indicate that propranolol is blocking the stress response, which may be related to GI issues (19:25). Future research will include transcutaneous vagus nerve stimulation (tVNS) to test the effect of parasympathetic nervous system (rest and digest) activation on GI symptoms (23:45). 

Ongoing work

The research outlined to this point has been strictly lab-based, and the speaker highlights the need for real-world “ecological” monitoring of stress behavior. Lab studies are often stressful in and of themselves, so they may not reflect real-world functioning. Ferguson’s ongoing study, funded by ARI, aims to examine differences in verbal social communication data from 30 autistic people with GI symptoms and 30 without over a three-week period. Data will be collected using smartwatches that track pulse-rate variability, or the time variation between heartbeats, measured with photoplethysmography (PPG). Researchers will also examine differences in autonomic nervous system functioning in relation to GI symptoms (25:30). 

Verbal and social activity will be recorded on a smartwatch app that Ferguson and his team developed called “CORE Autism (31:47).” The app measures the total time spoken by a participant. It has reached 90% agreement between what researchers hear and what the algorithm hears (35:35). The speaker underscores the importance of real-world data and how much we miss with typical laboratory-based questionnaires. Researchers hypothesize that pulse rate variability will be significantly lower for the group with GI issues, indicating a higher stress response. They also hypothesize that there is less social communication among the GI group, possibly due to increased stress (36:48).

Ferguson emphasizes that findings from this study will provide real-world evidence of stress and sociability, allowing a potentially different take on the connection between GI issues and stress for autistic people. For example, if stress is heightened in the GI group, implications for treatment could be huge. The presenter notes that more research could be done to address what happens to GI symptoms when stress is addressed and vice versa (37:45). This study will be finished in 2026. 

Summary

Ferguson reviews the presentation, highlighting that GI symptoms like constipation are prevalent in autism and often associated with stress response and internalizing behaviors, which may differ by age. The stress response may also precede problem behaviors in autism, providing treatment options based on stress reduction via pharmacological, vagal, and behavioral avenues. While preliminary data are exciting, more research is needed in these areas (39:35). Ferguson provides thanks and acknowledgments before the Q&A, where he discusses enteroception, SSRIs, nutrition, smartwatch usage, and more (42:00). 

Originally published November 19, 2024

This is a joint presentation by ARI and the World Autism Organisation.

Professor Carmelo Rizzo, MD, discusses adverse reactions to food and the critical role of intestinal microbiota in autism. He outlines the history of clinical nutrition and highlights the role of chronic inflammation in disease pathology. The presenter considers the interplay of inflammation, altered gut absorption, and food intolerances, underscoring the high occurrence of GI issues in autism and their correlation to behavioral characteristics. Rizzo discusses implications for clinical practice before the Q&A. 

This is a joint presentation by ARI and the World Autism Organisation.

Handouts are available HERE

In this webinar: 

0:00 – WOA & ARI introduction
6:10 – Speaker background and introduction
9:30 – Total load effect
12:30 – Clinical nutrition
15:44 – Food adverse reactions & inflammation
19:45 – Stress response theory
23:00 – Food intolerance vs. food allergy
24:50 – Altered gut absorption
29:00 – Food intolerances
31:30 – The gut microbiome
34:50 – Microbiota and autism
40:28 – Clinical implications
41:45 – Q&A

Introduction

Rizzo explains the total load effect as the idea that our overall health depends on numerous factors, including genetics, emotional and physical environments, inhalants, electromagnetic fields, and nutrition, to name a few (9:30). He highlights nutrition as a critical aspect of prevention and care for many conditions, citing research on the connection between food allergies, behavior, and diet from the early 20th century. Basic principles of clinical nutrition emphasize removing the toxin or chemical and repairing any chronic damage/inflammation, particularly to sensitive organs (12:30). The presenter notes pioneering researchers in ecology and how their work has impacted how contemporary researchers and practitioners understand complex neurological conditions (13:25). 

• Neuropathic manifestations in infants and children as a result of anaphylactic reaction to foods contained in their dietary (Shannon, 1922)
• Elimination Diets and Patient’s Allergies. A Handbook of Allergy (Rowe, 1944)

Food adverse reactions & inflammation

Food adverse reactions include allergies, pseudoallergies, hypersensitivity, toxic reactions, and food intolerances, all of which can lead to inflammation  (15:44). Rizzo describes how inflammation keeps us alive by destroying bacteria and viruses but how it can cause intense injury to organs and tissues if not addressed. Inflammation occurs differently in each person and can manifest in multiple ways simultaneously. Common external presentations of inflammation include osteoarthritis, sore throat, eczema, rhinitis, migraines, and multiple sclerosis (17:30). The presenter notes the connection between inflammation and depression, cancer, obesity, Alzheimer’s, and heart disease, underscoring the importance of correctly identifying and addressing chronic inflammation (18:40). 

Rizzo defines stress as a non-specific response of the body to harmful stimuli (19:45). To illustrate immune system function under the stress theory, he uses the analogy of a barrel holding water (functioning). At first, it holds well based on its build (genetics) and age, but the barrel can only hold a certain amount of water (adapt to a certain point). If the water flow (environmental stressor) doesn’t stop, water begins to spill out of the barrel (physical manifestation/symptom). Those with a full barrel develop food or chemical imbalances that present as conditions or symptoms (20:40). The speaker describes complementary science, underscoring the ability to identify what substances should be added or removed from the body based on specific indications (22:00). 

Altered gut absorption

The speaker highlights the importance of intestinal microbiota in the creation and absorption of crucial vitamins and nutrients, noting the specific balances required for proper immune function (24:50). He details the layers of the intestinal barrier and underscores the role of the mucosal immune system within the gut (26:25). Alterations to the intestinal barrier cause gut permeability, allowing macromolecules into the body where they may be recognized as foreign and activate the body’s defense mechanism. Anything from genetics to emotional stress can cause changes in the gut microbiome (27:45).

Food intolerances

Food intolerances are characterized by an inability to absorb or metabolize certain nutrients, causing an abnormal reaction to specific foods (23:00). Rizzo provides examples of biological food families and highlights their importance in addressing food intolerances. If ingestion of foods within the same family continues, he explains, the body won’t properly detox, and intolerance will persist (29:00). Food intolerances can manifest in any organ, and the reaction window is 72 hours, so what feels like a direct reaction to one food could be a buildup of inflammation in the body (30:10). Symptoms related to food intolerances occur in the central nervous system (headache, depression), genital-urinary systems (vaginal irritation, cyclic cysts), respiratory systems (nasal congestion, rhinitis), skeletal muscle (muscular cramps, articular cogency), gastrointestinal tract (nausea, IBS, Crohn’s disease), and skin (eczema, rash, facial paleness) (31:15).

The gut microbiome

The intestinal microbiota is composed of billions of cells and is one of the largest, most complex bacterial ecosystems on the planet (31:30). Rizzo discusses the development paths and general functions of the gut microbiota for infants, children, adults, and the elderly (32:30). The microbiome’s metabolic functions, such as vitamin production and amino acid synthesis, make it a critical factor in disease prevention and care (34:00).

Microbiota and autism

Individuals with autism have unique intestinal bacterial populations correlated with various autism traits. The presenter outlines a 2005 study on autism-related behaviors and GI experiences with more than 900 participants (34:50). The most common GI disturbances reported were constipation (48%), diarrhea (28%), abdominal pain (55%), and gastroesophageal reflux (10%), with an inflammatory index of 40% (37:20). Histological (tissue and cell structure) findings showed esophagitis, chronic gastritis, colitis, and eosinophilic gastritis (38:08). Participants were prescribed pharmacological and dietary interventions. 

At a twelve-month follow-up, 150 participants reported improvements in GI pain (64%), bowel complaints (84%), reflux (41%), muscle mass (40%), hyperactivity/aggression (65%), attention (34%), and sleep-wake rhythm (22.1%). Rizzo asserts that these findings indicate that anxiety, sensory-responsivity, and GI issues are interrelated phenomena for people with autism (38:50).

• Anxiety, Sensory Over-Responsivity, and Gastrointestinal Problems in Children with Autism Spectrum Disorders (Mazurek et al., 2013)

Implications for clinical practice

Outside of autism, the gut microbiome is central to the prevention and care of type two diabetes, cardiovascular diseases, liver disease, hyperlipidemia, and many other conditions (34:50). Understanding the integral role of the gut microbiome in systems across the body must be a priority for clinical research and practice (40:28). Rizzo concludes that the development of the microbiota field must involve cardiologists, allergists, psychiatrists, and other specialists concerned with pathological conditions (40:43). He provides thanks before the Q&A session where he discusses chronic inflammation, biological food groups, and much more (41:45)

Dr. Calliope Holingue, MPH, Ph.D., provides an overview of the intersection between the gut, autism, and well-being. She outlines recent studies on the GI needs and experiences of autistic individuals and discusses the complex pathways of connection between the gut and autism. The presenter summarizes GI-autism research to date, highlighting the need for screening tools specific to autistic GI experiences. Diet change and Fecal Matter Transplant are outlined as microbial interventions in autism. Holingue provides tips for recognizing GI distress and discusses future directions for research and interventions before the Q&A. 

In this webinar:

1:00 – Outline
1:50 – Autism and gastrointestinal issues
4:15 – Common GI symptoms
6:20 – Study: Qualitative study of families with autistic children with GI issues
12:00 – Study: GI experiences and needs of autistic adults
16:20 – Linking GI symptoms and autism
21:04 – Intersection of autism and GI research
25:55 – Microbiome interventions in autism
32:10 – Fecal matter transplant (FMT)
34:00 – Study: Autism and microbiota transfer therapy
39:55 – Recognizing GI distress in autism
43:05 – Quotes from parents
44:24 – Gastrointestinal and related behaviors inventory (GIRBI)
45:50 – Future directions
47:45 – Q&A

Autism and gastrointestinal issues

Holingue outlines common clinical characteristics of autism and explains how co-occurring medical conditions affect autism heterogeneity (1:50). People with autism often have complex healthcare needs but consistently experience a lower quality of care and assistance across their lifetime (3:05). The speaker explains that gastrointestinal (GI) issues like constipation, diarrhea, and abdominal pain are incredibly common in autism, occurring in 47% of autistic participants in a recent meta-analysis (4:15). She notes that GI distress has been linked to co-occurring conditions like seizures, sleep disorders, and functional behavior difficulties (5:30). 

Study: Qualitative assessment of GI issues in autistic children and their families

The speaker outlines her 2022 publication in Autism, assessing the experiences of autistic children with GI issues and their families. Researchers derived four main themes from 12 parent interviews (6:20). First, autistic children often have difficulty verbally communicating the presence of GI symptoms, and second, GI issues impact a child’s overall well-being and ability to fully engage in activities like school or social gatherings (7:40).

The third theme to emerge was how GI issues impact the family’s well-being due to parental frustrations, financial stressors, and limitations on family activities (9:00). Finally, theme four highlights the challenges parents experience with finding accessible quality care for their children. Many noted lengthy, complicated processes, medical offices not conducive to autism, and a lack of education and experience in healthcare providers (10:12). 

Study: GI experiences and needs for adults with autism

Holingue outlines a study exploring the GI experiences of autistic adults (in preparation for publication). The study aims to investigate the needs and priorities of autistic adults and develop recommendations for research and support (12:00). Similar to the first study, participants said that GI symptoms profoundly impact their ability to create relationships, work, and live comfortably (overall well-being). They also described common triggers for GI issues, including stress, sensory overwhelm, and changes in routine, and highlighted frustrating and unhelpful experiences with the healthcare systems (13:15). To improve GI health in autistic adults, the researchers recommend more training around interoception, anxiety, and advocacy for adults with autism. Similarly, they assert the need for increased healthcare provider training on assessing and treating complex health issues and autism accommodations (15:15). 

The intersection of autism and GI issues

Pathways of connection

Holingue claims that pathways linking autism and GI issues are complex. For example, common co-occurring conditions, like anxiety, sleep problems, and restrictive diets, drastically alter the gut microbiome (16:20). Similarly, GI symptoms can exacerbate irritability, anxiety, and other behaviors related to pain or discomfort (19:00). The presenter touches on biological pathways that interact with GI health including the microbiome, vagus nerve, immune system modulation, gut permeability, and serotonin production (20:14). She explains that maternal microbiomes interact with fetal immune systems and how early life exposures shape the development of the microbiome (i.e., delivery mode, diet/breastfeeding) (29:00). 

History of GI-autism research

The speaker outlines autism-GI research starting from the early 2000s. She briefly summarizes initial observations (21:04), the discovery of the gut-brain axis (22:15), how microbiome diversity can inform behavior and treatment (22:40), and the beginning of intervention studies (23:35). Contemporary research, Holingue continues, focuses on understanding the mechanisms by which the gut microbiome influences the brain and how the environment influences the composition of the gut microbiome (24:30). 

Microbiome interventions in autism

Microbial interventions hold promise in autism because they are modifiable for individuals across heterogeneities. The speaker notes that most studies to date are strictly pediatric (25:55). Findings across the field are divergent and inconclusive due to small cohorts, different comparison groups, and autism heterogeneity (26:30). The presenter asserts that failure to control for potential confounders, or other things that could impact the microbiome (i.e., diet, antibiotics, medications, etc.) is a major limiting factor across studies. 

Diet change is a common intervention that affects gut microbial composition (30:50). Holingue describes fecal matter transplant (FMT), where a healthy donor provides feces (after extensive screening and safety measures), which contains microbiota needed by someone with a specific health condition. The cleaned microbiota is delivered to the recipient via pill, drink, or endoscopy (32:10). She discusses the difference between intestinal mucosa (fecal matter) and the microbiome, noting the safety and ethical nuances associated with FMT (28:00). 

Study: Autism and microbiota transfer therapy

Holingue outlines an FMT study by Kange et al. (2019) in which parents collected stool samples and recorded symptoms during treatment (35:12). Microbiome results showed that autism gut bacteria were less diverse at baseline but increased throughout the treatment, ending with a similar composition to controls. Some long-term effects were recorded (35:20). There was a significant correlation between changes in GI composition and autism behaviors, meaning that as GI symptoms improved, associated behaviors decreased. The treatment was generally well tolerated, with few temporary adverse effects (36:16). The speaker discusses study limitations, including a lack of a placebo group and randomization (37:20). She considers the difficulty and importance of disentangling treatment effects from other drivers and notes the small sample size in this study (38:10). 

Recognizing and treating GI issues in autism

The presenter briefly discusses symptoms and signs of GI distress in autism (39:55). She underscores that children, in general, have difficulty communicating pain and that this is often exacerbated in children with neurodevelopmental conditions (41:00). Holingue discusses a recent analysis that found that symptom estimates vary according to how they are measured (i.e., parents/practitioners/complex data) and that existing measurements were not developed for the autistic population (41:44). 

Parents are often relied on to detect GI problems in their children. The presenter lists some tell-tale signs of GI distress in autistic children and asserts the need for assessment tools specific to GI experiences in autism (42:35). She outlines the Gastrointestinal and Related Behaviors Inventory (GIRBI), which assesses symptoms, bowel movements, and other behaviors potentially related to GI issues (44:24).  Results from the pilot GIRBI questionnaire show high convergent validity, high sensitivity in predicting parent-report diagnosis, and a 7-factor solution to recognizing GI issues in autism (45:40). 

Future directions

The speaker asserts that future work on GI measurements should include multiple versions of the GIRBI, with specific attention given to adults and older adults with autism. Future assessments should also incorporate biospecimens with report measures and include self-reports, caregiver reports, and more clinical evaluations (45:50). Holingue provides thanks and acknowledgments (47:12) before the Q&A, where she discusses food allergies, gluten vs. celiac, recommended diets, advocacy in medical settings, and how modes of delivery impact an infant’s gut (47:45).

In this brief overview, neurologist Margaret Bauman, MD summarizes symptoms and signs of medical comorbidities that frequently occur, but may go unrecognized, in patients diagnosed with ASD. While the underlying cause of autism spectrum disorder (ASD) is generally unknown, scientists suspect that it is a multifactorial condition affecting multiple body systems.

Margaret Bauman, MD, discusses medical comorbidities associated with autism and how they affect behavior and quality of life. She outlines some common physical comorbidities, including seizure (1:41), sleep (2:18), hormonal (2:47), urinary (3:00), and gastrointestinal (3:33) disorders, and details how these issues present differently in autistic individuals (1:30). Bauman describes our understanding of challenging behaviors in autism as a form of communication (1:00) and highlights the importance of knowing the signs (6:50).

Individuals with communication difficulties may not be able to describe what hurts or where (4:00). Similarly, sensory issues make it difficult for individuals to determine what is happening in their bodies (5:18). Therefore, Bauman recommends, “… individuals on the spectrum who demonstrate behavioral problems absolutely merit a good physical [and] medical workup (6:41)…. [and] gastrointestinal disorders… need to be one of the first areas of investigation (4:45).” She also suggests that providers who have experience working with individuals with autism be recruited to help create necessary interventions and best outcomes (7:46).