Nutritional factors and autism in small children

Around 60% of individuals diagnosed with ASD also report gut complaints. Does this mean that the psychological symptoms of ASD and the digestive problems have anything in common? Will understanding of the role of gut microbiota be a new avenue to answer some of the burning questions regarding the etiology of ASD?


To answer these question scientists from KIND in collaboration with Rochellys Diaz Heijtz from Deparment of Neuroscience at KI started a new study using an on-line questionnaire. They gather information from parents regarding the gastrointestinal (GI) complaints and factors which could have influenced the development of their childrens’ gut flora. The target research group includes families which have at least two children below the age of 10 and includes children with and without ASD.

GI complaints in children with ASD

Parents often inform clinicians about the GI complaints in their children suffering from ASD. Nevertheless, for a long time it was not certain whether GI symptoms are more common between ASD sufferers. A recent meta-analysis of results from articles published since the year 2000 has shown that children with ASD report more general GI complaints (e.g. belly pain, diarrhea) than children without ASD. At this stage it is, however, impossible to link any specific GI complain or organic pathology of digestive tract to ASD.

Currently, it is not possible to state whether there is a cause-effect relation between GI problems and ASD. What we know for sure is that the extreme food selectivity often observed in ASD can be both the cause and the effect of GI problems. Furthermore, some studies suggest that unreported GI problems can be manifested in sleep problems, aggression, irritability and other behavioral problems of children with ASD. Finally, the diet and the feeding pattern both have strong influence on the composition of the gut microbiota. Therefore, there is a need for studies which assess the GI complaints and nutrition from birth in children with ASD.

What is the role of bacteria in the gut?

More than 1000 strains and more than tens of trillions of organisms results in up to 2 kg of biological mass in the gut. All these bacteria together serve important functions including digestions of food, production of some vitamins etc. Each one of us possesses a unique composition of bacteria in our intestines and this may results in personal differences in digestion and metabolism. Some studies, for example, show that the gut bacteria composition may be one of the factors predisposing to obesity. Other studies show its role in the development of immunity.

How can bacteria in intestines influence brain function?

Accumulating body of evidence shows that bacteria present in the gut have an influence on the functioning of the brain. This means that disturbances in microbiota balance in our intestines may have consequences for our emotions, cognitions and behavior. The mechanisms are still not well known. There are, however, various ways in which bacteria in the gut could influence brain. For example, some studies suggest that Bifidobecteria infantis could influence tryptophan metabolism which could lead to changes in serotonin levels (one of brain neurotransmitters). Another possible route of mutual communication between gut mictobiota and the brain is the vagal nerve.

What are the factors influencing the gut flora?

Important fact to remember is that babies are sterile in womb but the gut becomes colonized by bacteria during birth. This means that all our microbiota is acquired from the mother during the delivery and from other sources during the whole life. Therefore, multiple factors, present at different time points in development have an influence on the gut microbiota. Mother’s microbiota can be influenced by mother’s diet and health problems including infections. Child’s microbiota will change depending on the way of deliver (natural, c-section etc), gestational age at birth, breast feeding pattern, infections, medication, diet etc.

Research details

Based on all these above mentioned facts, researchers from KI aim at gathering data from 300 families in which one child has ASD or both children do not have the condition. They compare the different factors present during children development and try to establish which of these factors could influence the development of autism. Special attention is put on breast feeding duration and gradual introduction of solid foods. Additional group of questions regards mother’s and child’s health problems as well as reported digestive problems.

The recruitment for the study has ended. Thanks to all the parents who participated.

Related links:

More about research on autism and nutritional factors: Arizona State University Autism /Aspergers Research Program

Learn more about gut microbiota: Gut Microbiota World Watch

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Johan Isaksson

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