According to newer medical research, children with autism seem to have less diverse gut bacteria in their microbiome compared to their neurotypical peers.

While the interaction between the microbiome, brain health, and developmental or behavioral health is complex, finding ways to diversify your child’s gut microbiome — through a healthy diet and, with guidance, dietary supplements — can potentially improve your child’s behaviors.

When your child feels better, they may have reduced feeding problems, which are often a struggle for children with autism.

What Are Gut Bacteria?

Although we often think about bacteria as bad because they cause disease, the human body actually needs bacteria in the digestive system to function.

We have about 100 trillion bacteria in our gut, comprising around 1,000 species and 5,000 distinct strains. The bacteria break down the food we eat so we can get as much nutrition as possible out of it. Our gut bacteria are often referred to as the microbiome or flora.

How Can Gut Bacteria Impact Mental & Physical Health? 

Medical research is still uncovering much of the impact the microbiome has on overall health. Your microbiome not only affects your digestion, but it has also been correlated to mood and mental health, cardiovascular health, muscle and joint health, metabolism, immune health, and even your risk of cancer.

Your age, genetics, environment, current diet, and medication history can all impact your gut microbiome. For example, if you needed a long course of antibiotics, you may suffer some digestive issues as a result.

A Potential Link Between Gut Bacteria & Autism

While the current medical research on gut bacteria and overall health is relatively new, and shows correlation more than causation, it can be a starting point for understanding how digestion and nutrition affect the brain and body.

People with autism tend to have more gastrointestinal or digestive issues compared to the general population. This could stem from feeding problems like food aversions. However, many medical studies suggest that feeding problems can develop from digestive issues that cause discomfort or pain.

People with autism, including children, are more likely to struggle with diarrhea, constipation, and indigestion compared to their neurotypical peers. This could cause children, in particular, to move away from certain foods they associate with discomfort, struggle to transition to new foods, or feel stress around mealtimes.

However, the 2013 study published in PLoS ONE did not find a correlation between the density of gut bacteria and the severity of behavioral and physical struggles in children with autism. The researchers thought that children with less diverse microbiomes would have more severe symptoms, but this was not the case. Still, the study did show that children with autism have less diverse gut microbiomes than neurotypical children.

Could Gut Bacteria Influence Behavior?

A more recent study conducted on mice, published in 2019, found a closer relationship between gut bacteria and brain health.

Per the study, when mice had their gut microbiomes replaced with fecal matter from people with autism, the change seemed to cause autism-like behaviors in the mice. The researchers were clear that this did not prove that autism is caused by gut bacteria, but that behaviors could be triggered by certain gut-related experiences which could, in turn, affect brain chemistry.

The researchers recorded how often these mice vocalized and how often they interacted with other mice, compared to microbiome-typical mice. The scientists also scattered marbles across the cage as a way to estimate repetitive behaviors seen in children and adults with autism. They counted how many marbles the test mice buried.

The mice who received replacement gut bacteria from children with autism vocalized less, interacted with other mice less, and displayed more repetitive behaviors. When researchers dissected the brains of the affected mice, they found differences compared to neurotypical mice, suggesting that gut bacteria had some involvement in brain formation, which would then influence behavior.

Modern Research on Autism & the Gut

A study examining the microbiomes of children with autism found that autistic children had fewer types of intestinal bacteria compared to their neurotypical peers. However, the study did not find that the lack of gut bacteria diversity correlated to the severity of gastrointestinal problems.

Separate research suggested that problematic types of gut bacteria, or imbalances in gut bacteria, could contribute to types of inflammation that caused discomfort or pain. This discomfort could increase maladaptive behaviors like social avoidance, poor communication, repetitive behaviors, and problems at mealtimes or with food, because the child is uncomfortable and cannot describe why.

Another study, also published in 2019, found that a gene mutation that impacts how neurons communicate in the brain also changed some gut function. The research began with an early paper, from 2003, investigating the potential genetic link to autism. The newer research found that certain genes changed how neurons communicate with each other in the brain and found some correlation with gastrointestinal dysfunction.

Supporting Good Digestive Health 

Here are some general recommendations for improving gut health:

  • Eat fermented foods. Yogurt, kefir, pickles, sauerkraut, kimchi, miso, and other foods are fermented, and you can often find “live cultures” versions in your local grocery store. Including fermented foods in your diet keeps your gut healthy by replenishing healthy bacteria and yeasts, and keeping the balance in your stomach and intestines.
  • Consume a balanced diet. Eat enough fruits, vegetables, whole grains, and lean proteins to keep your digestive system happy, and to ensure you are getting enough vitamins and minerals to support your overall health. This typically keeps your gut bacteria in check too. In some cases, you may need some additional support for your gut health.
  • Try probiotic supplements. If your child is picky about foods and the flavor or texture of fermented foods does not appeal to them, you can try a probiotic supplement instead. Supplements move through the digestive system differently than food, but your child can still benefit from the nutritional support they bring.

While dietary changes, vitamins and supplements, and other methods of supporting gut health can be vital aspects of helping your child on the autism spectrum, these methods should be used in conjunction with behavior therapy. Applied behavior analysis (ABA) is the leading approach to managing autism symptoms and promoting positive behavioral changes in children and adults who are on the spectrum.

Talk to your child’s doctor before you implement nutritional changes. If you are interested in adding dietary support to your child’s treatment plan, your child’s therapist, pediatrician, and other specialists can help you find a nutritional therapist. This professional guidance can be crucial to ensuring your child gets the balanced nutrition they need.