The gut-brain connection

Do you remember learning about the systems of the human body? It’s pretty amazing, when you think about it – all the biological, chemical and physical processes going on so that we can move, think, and do what we do.

For instance, when our digestive system does its job, our body gets the energy and raw materials to make all these processes happen. Yup, that’s all our digestive system does … OR IS IT??

Increasingly, scientists have been researching the two-way communication between the brain and the gut. That’s right: two way. Not only does our bossy brain send signals to our intestines; what’s going on in the gut can influence what’s going on in our noggin.

“Well sure,” you might say. “When I have intestinal distress, I get cranky and worried.”

Point taken. But we’re talking about an influence extending much beyond those times of woe.

In a further surprise, many researchers are focusing not on the actual intestines, but what’s living inside them.

From what I see being reported lately, the focus is on the bacteria in our gut – something like 40 trillion of the little darlings, according to this article in Medical News Today. While 30 to 40 species of bacterial beasties typically occupy human intestines, there can be any of 1,000 varieties.

Instead of calling them out one by one (now that would be a long blog post!) let’s refer to the bacteria collectively as the microbiome. The main point is that imbalances in the composition of the microbiome have been linked to anxiety, depression, memory functioning, hyperactivity, obsessive-compulsive disorder, and autism.

(Regarding autism, here’s a quote from the Medical News Today article: “Children with autism often have abnormal and less diverse communities of bacteria in their gut.” Wow.)

Furthermore, early indications are that changing the composition of the microbiome can lessen some adverse mental traits.

The studies most often involve lab mice – depressed or anxious mice, or mice that have learned something and then have their microbiome messed with. (Laboratory mice: we salute your service!) You can read about some of the experiments here. For instance, bacteria transplanted from a daredevil mouse to a chronically anxious mouse makes the anxious mouse braver.

A mouse reading this news is bound to be fascinated or very concerned, but of course the real point of these experiments is whether we can get the same results in humans. Limited studies with people have shown promise so far.

Even so, we are probably years away from this kind of therapy being readily available. A Science News article talks about what stands in the way:

Figuring out what’s being said in this body-microbe exchange, and how to shift the tone in a way that improves mental health, won’t be easy. For starters, no one knows the exact ingredients for a healthy microbial community, and the recipe probably differs from person to person. And it’s not always simple to deliver microbes to the gut and persuade them to stay. Nor is it clear how messages travel between microbes and brain, though scientists have some ideas.

Scientists do know that certain species of gut bacteria produce neurotransmitters that influence mood and behavior, as shown in a table in the Science News article. The vagus nerve, which connects the gut and the brain, seems to play a part in the communication. The immune system could also be a player. We need to understand more before we start mucking about with widespread treatments.

You might ask, what exactly would be done to change the microbiome in a human body for the better?  One medical procedure that I’ve seen discussed is not at all pleasant to think about. Two words: fecal transplant. Yuck!

If you managed to keep reading past that last paragraph, you’ll be happy to know that the microbiome can also be changed by what we ingest. You’ve probably seen products that boast of containing probiotics, or good bacteria. These include particular types of yogurt, kefir, and supplements containing probiotics.

One of the scientists doing research in this area is Mark Lyte, at the Texas Tech University Health Sciences Center in Abilene, Texas. Read his poignant but cautionary quote from an article in the New York Times:

‘‘My main fear is the hype is running ahead of the science.’’ He knew that parents emailing him for answers meant they had exhausted every option offered by modern medicine. ‘‘It’s the Wild West out there,’’ he said. ‘‘You can go online and buy any amount of probiotics for any number of conditions now, and my paper is one of those cited. I never said go out and take probiotics.’’ He added, ‘‘We really need a lot more research done before we actually have people trying therapies out.’’

To make potentially beneficial changes to gut bacteria, one could also add more foods with prebiotic properties to the diet. Such foods encourage the growth or activity of good bacteria (probiotics). Foods that are notable sources of prebiotics include garlic, onion, asparagus, leeks, dandelion greens, and wheat bran.

Rounding out my literature review of the topic is this article from Psychology Today. The whole article is interesting, but it has a few passages that may apply in particular to our neurodiverse kiddos. See what you think:

In addition to influencing daily functioning, there is also growing evidence that there are particular “windows” during development of the nervous system when its very threshold of responsiveness is set by the diversity of bacteria that make up the microbiome. Those periods—pre- and perinatal development and again at adolescence—may be especially critical in creating susceptibility to or resilience to stress throughout the lifetime.


Antibiotic treatment of infection, consumption of a poor diet, and stress have all been shown to disrupt composition of the gut bacteria, affecting the substances such bacteria produce and the signals they send. But it may be that diet, antibiotics, and stress also change the function of the gut in ways that activate immune cells, which, by stirring inflammation in the brain, induces psychiatric symptoms.

Adolescence is a period when brain connectivity undergoes major change. It is also a time when many psychiatric disorders first appear. According to neurovirologist Robert Yolken, adolescents may be especially susceptible to the psychiatric effects of gut-bacteria shifts resulting from antibiotic use. Infection prevention and control, in fact, may be the next frontier of mental illness treatment.

What? You mean we parents shouldn’t have given our kids all those rounds of antibiotics prescribed for ear infections and the like?

Let’s all try not to sink into a puddle of guilt over possible neuropsych disruption caused by what in our house was called “pink medicine.” It’s uncertain what’s really causing all these brain-gut relationships. Is the brain in charge, or is the bacteria, or is it both sometimes, or do they ever trade? So much is still unknown.

I’m interested to see where the findings will lead. No one should be making any promises yet, but if our struggling neurodiverse kids are willing to get more probiotic or prebiotic foods in their diet, it seems like doing so may turn out to have brain benefits as well as general health benefits.



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About janet565

I've lived in the Inland Empire of Southern California since 1982. My profession involves maps and geography. I hope you find the blog useful, and wish you well....

2 responses to “The gut-brain connection”

  1. jofox2108 says :

    I suspect that on average children with autism have less diverse gut bacteria because a large number of these children eat extremely restricted diets. So the autism causes the lack of gut bacteria, rather than the other way around.


    • janet565 says :

      Yes, that’s one of the “chicken or the egg” questions in this whole line of research. Thanks for pointing that out! Even with that, it leaves the possibility that altering the gut bacteria in someone with autism may help with some of their more troublesome symptoms.

      Liked by 1 person

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