Believe it or not, you’ve got two brains. One sits between your ears inside your skull and the other? It’s in your gut and they have quite a good relationship. You may have heard it referred to as the gut-brain connection. But, how are they connected?
If you have ever experienced anything such as nausea and that raw “butterfly” feeling in your stomach, that’s actually your gut-brain connection in action. It happens because your gastrointestinal (GI) tract sensitive to emotions ranging from joy to anger, calmness to stress, and everything in between.
Basically, in the same way an unhealthy brain will shoot your stomach signals when it’s distressed, a distressed stomach will send signals to your brain. Depending on how affected either brain is and for how long, numerous health problems can arise.
Evidence of Poor Gut Health on the Brain
According to the National Institutes of Health, each individual’s “gut microbiota consists of tens of trillions of microorganisms and can weigh up to six pounds. We acquire much of this bacteria as infants when we pass through the birth canal during delivery, but other factors, such as antibiotic use or birth by Cesarean section, can influence bacterial levels.”
Numbers like those are hard to wrap your head around, but it goes to show how significant the gut is to overall health and well-being. A September 2017 study published in the journal Clinical Practice explored the gut microbiota’s effect on mental health.
Researchers reviewed the growing body of evidence suggesting that poor or insufficient microbiota can not only lead to GI tract diseases, but also mental illnesses including anxiety, depression, schizophrenia, and autism.
In a March 2017 Current Obesity Reports study, researchers tried to answer whether gut microbiota was linked to obesity and central nervous system disorders. After reviewing much of the leading edge experimental and epidemiological evidence, they concluded that the state of one’s gut is intimately related to their increased risk of developing obesity and mental illnesses. Gut health of individuals with autism spectrum disorder (ASD) was of particular interest:
“[ASD] patients suffer from gastrointestinal dysfunction, including deficiencies in GI motility and enhanced intestinal permeability. There is an increased prevalence in IBD among ASD young individuals when compared to controls.”
The Link Between Gastrointestinal Issues and Individuals with ASD
Scientists are fully aware that most children with autism suffer from some form of gut-related health problem. To date, however, the reason why has remained unclear. Now, professor in the Department of Medical Microbiology and Immunology, Paul Ashwood, and graduate student Destanie Rose believe they have some answers!
In the journal Brain, Behavior, and Immunity, Ashwood and Rose studied 103 children between 3-and-12-years-old and split them into four groups:
- Children with ASD with gastrointestinal symptoms
- Children with ASD without gastrointestinal symptoms
- Typically developing children with gastrointestinal symptoms
- Typically developing children without gastrointestinal symptoms
The researchers from the UC Davis MIND Institute took blood and stool samples from each group and analyzed two things: immune response and microbial makeup.
Compared to the other three groups, it was the children with both ASD and gastrointestinal symptoms who showed the most distinctions. Ashwood and Rose highlighted four in particular:
- Higher levels of inflammatory cytokines
- Higher levels of a protein (i.e., zonulin) found in the gastrointestinal tract that heavily influences gut permeability
- Lower levels of a protein (i.e., TGFβ1) responsible for regulating immune response
- An overall difference and shift in gut microbiota
“Some children with ASD have this decrease in regulatory cytokines, which leaves them more prone to inflammation,” said Rose. “This increased inflammation may manifest as GI symptoms, allergies, asthma or some other form.”
What Does This Mean for Autism Treatments Moving Forward
Perhaps the most significant aspect of this study relates to the gastrointestinal symptoms. It suggests that gut health might be (and probably is) at the root of autism spectrum disorder. In an era where treatments are few and far between, and usually involved drugs, this study should give families and organizations hope for more holistic ASD treatments!
“It’s significant that the regulatory aspect of the immune system is decreased, which puts them at risk for inflammation,” said Rose. “Many studies point to different types of inflammation, and I think this one kind of summarizes why all those other findings can be true at the same time.”
While Ashwood acknowledges the road ahead is long, he is hopeful in that “[it’s] a step toward understanding co-morbidities that are present in at least half of children with ASD and working out which of these children may respond well to certain types of therapies. Although it’s still early, this work suggests we need to find ways to ease inflammation to help these children.”
ASD Affects Older Women, Too, So Keep Reading: Why So Many Women are Living with Autism and Don’t Even Know It
 Harvard Health Publishing. (n.d.). The gut-brain connection. Retrieved from https://www.health.harvard.edu/diseases-and-conditions/the-gut-brain-connection
 4 Fast Facts about the Gut-Brain Connection. (2017, September 24). Retrieved from https://nccih.nih.gov/news/events/IMlectures/gut-brain
 Clapp, M., Aurora, N., Herrera, L., Bhatia, M., Wilen, E., & Wakefield, S. (2017, September 15). Gut microbiota’s effect on mental health: The gut-brain axis. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5641835/
 Ochoa-Repáraz, J., & Kasper, L. H. (2016, March). The Second Brain: Is the Gut Microbiota a Link Between Obesity and Central Nervous System Disorders? Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4798912/
 Differential immune responses and microbiota profiles in children with autism spectrum disorders and co-morbid gastrointestinal symptoms. (2018, March 20). Retrieved from https://www.sciencedirect.com/science/article/pii/S0889159118300783
 UC Davis Health System, & Public Affairs and Marketing. (n.d.). Immune system and gastrointestinal deregulation linked with autism. Retrieved from http://www.ucdmc.ucdavis.edu/publish/news/mindinstitute/12807