Autism, or autism spectrum disorder (ASD), is a complex developmental condition that affects communication, behavior and social interaction. It is often marked by repetitive behaviors and highly focused interests. While the exact causes of autism remain unclear, what we do know is that its prevalence is rising. One out of every 31 eight-year-olds in the U.S. has been diagnosed with ASD.

Autism can shape daily life in unexpected ways. Children with autism are about five times more likely to be selective—or “picky”—eaters. They may avoid certain foods because of their texture, taste or smell. These restricted diets can make mealtimes stressful for families, can influence the type of bacteria that live in the digestive system and may affect overall health .

The gut-brain axis plays a key role in ASD. Studies have shown that gut bacteria may play a role in some behaviors and brain functions linked to ASD.  The gut-brain axis refers to the complex way that the gastrointestinal (GI) tract and the brain communicate with each other. In many children with ASD, the gut microbiome shows a decreased abundance of beneficial bacteria, alongside an increase in potentially harmful bacteria.

Some studies suggest that ASD may be linked to changes in gut microbiome chemicals, known as metabolites. The gut microbiome produces up to 40% of the body’s circulating chemicals, which help the gut and brain communicate. When these chemicals are altered, this gut-brain connection can be disrupted. In one study of children with ASD, researchers found lower levels of key metabolites, including one that helps produce brain messengers like serotonin. Serotonin is involved in a variety of bodily functions, including mood regulation, sleep and digestion.

Children with ASD are also more likely to experience gastrointestinal issues such as constipation, diarrhea, stomach pain and general digestive discomfort. Whether the GI problems or dietary habits come first is not clear. Repetitive eating patterns, where children prefer the same processed foods over and over again and often stick to rigid mealtimes, are common. Some researchers suggest that restrictive diets may worsen GI symptoms, while others believe that underlying stomach problems could contribute to selective eating. Restrictive diets combined with picky eating can also increase the risk of nutrient deficiencies, which can complicate health even more- leading to weaker bones and delayed growth.

Occupational therapy, sometimes combined with behavioral therapy, can help some children with ASD gradually eat more different types of foods. Although this is a promising approach, research in this area continues to uncover the complexities of autism. These studies bring us closer to creating strategies that can support both the gut and overall wellbeing in children with ASD.