Associations Between Dietary Composition and Gastrointestinal Symptoms in Autism Spectrum Disorder

Background:  Many individuals with autism spectrum disorder (ASD) have significant gastrointestinal (GI) symptoms, but the etiology is currently unknown. A previous study from our team found relationships between measures of autonomic nervous system (ANS) functioning and GI symptoms in ASD, especially for constipation. However, many individuals with ASD have altered diets which may affect GI functioning, and some may alter dietary composition in response to GI symptoms. Thus, it is important to examine dietary composition within the same sample of individuals from the aforementioned study to determine the possibility of diet interacting with the findings in this sample.

Objectives:  In order to assess for an association between diet and GI functioning in ASD, we examined dietary composition and GI symptoms in a subset of individuals from a previous study in which our team had found relationships between measures of ANS functioning and GI symptoms, particularly for constipation.

Methods:  A total of 80 individuals with ASD aged 6-18 who are enrolled in the Autism Speaks Autism Treatment Network (ATN) as well as general clinic patients at the University of Missouri Thompson Center for Autism and Neurodevelopmental Disorders participated in the study. A food frequency questionnaire assessing the child’s dietary composition over the previous month was completed by the child’s caregiver. The USDA Food Composition Database was utilized to provide comprehensive nutritional information for each food listed on the questionnaire, and the micronutrients and macronutrients contained in each food serving consumed over the past month were summed for each nutritional item (e.g., vitamins, minerals) for each participant. The child’s upper and lower GI tract symptomatology over the past two months was assessed by administering the Questionnaire on Pediatric Gastrointestinal Symptoms, Rome III to this child’s caregiver, and quantitative scores for upper and lower GI tract symptoms were created using a scoring rubric previously described by our research team.

Results:  Although initial analysis found that upper GI tract symptoms were associated with total dietary fiber (p=0.042) and vitamin B6 intake (p=0.003), neither was statistically significantly associated with upper GI tract symptoms after adjusting for the 32 nutrients examined. There was no evidence for an association between lower GI tract symptoms and any nutrient.

Conclusions:  These data suggest that nutritional composition is not associated with GI symptomatology in this sample of individuals with ASD. Therefore, variations in diet did not likely contribute to our previous findings of associations between GI symptomatology and ANS functioning as well as stress reactivity. Better understanding of other contributory factors will be needed to guide future research on the development of specialized treatments for those with ASD and co-occurring GI disorders.