Does the Gut Microbiome Affect Mental Health?

Magnifying glass inspecting bacteria in the gut

We all have trillions of microbes living in our intestines. This microbiome, which develops in infancy, plays a major role in our digestion, but there’s growing evidence that it affects more than just our digestive system.

This collection of critters weighs about 2 kg and includes bacteria, fungi, and viruses. There is no “normal” microbiome composition, but the more variability there is, the better it is for our health. What’s hanging out inside of us has a lot to do with what we eat, but it’s also affected by other factors, including stress and antibiotic usage.

The microbiome and mental health

What’s in our gut also influences what’s going on in our brain. Some gut bacteria may stimulate the vagus nerve, which connects the gut and brain. Much of our serotonin is produced in the gut, and the microbiome plays a role in that. Besides being transformed into serotonin, tryptophan can also be transformed into a neurotoxic substance, and the microbial mix may play a role in determining how much tryptophan goes to each pathway.

The microbiome appears to play a role in inflammation through a few different potential mechanisms, and depression and some other mental illnesses are thought to have an inflammatory component. Taking probiotics can help to reduce the levels of inflammatory markers in the blood.

One study found that overgrowth of a particular Candida species (a yeasty beastie) could contribute to the development of autism. Disruptions in the microbiome may also have a role in schizophrenia, mood disorders, and anxiety disorders.

How can we support gut health?

Dietary fibre is important to consume, as it provides food for certain helpful types of bacteria. Diets high in fibre have been linked to a decreased risk for depression and anxiety. Diets high in antioxidants and phytonutrients (micronutrients found in plants) help to promote greater diversity in the microbiome.

While taking probiotics may be beneficial, it’s not clear what specific composition of species or what dose would be most effective. Another option that’s being trialled is fecal microbiota transplants, something that’s currently used for treating recurrent Clostridium difficile infections. The University of Calgary is doing studies with a pill version (a pill o’ poop, if you will?), while Johns Hopkins University does it via colonoscopy for C. diff.

Interesting stuff, although I don’t imagine many people would be signing up for the pill o’ poop anytime soon. A few years ago I took probiotics regularly for maybe a year or so after I picked up a Giardia infection while travelling, which wreaked extended havoc on my gut. I don’t recall noticing any link to my mental health. I could certainly eat better than I do, but I don’t care sufficiently to do anything about it.

Do you think your gut and your brain are chatting?


36 thoughts on “Does the Gut Microbiome Affect Mental Health?”

  1. I don’t know how scientific my response is. But I do feel that my gut is an emotional center (one of many in the body) and for sure it communicates/speaks to my brain. And not just on matters of food, thirst etc. but on feelings. Great post Ashley thanks for the food for thought (ha! a pun😊)

    1. Great post! I do believe my brain talks to my gut, I don’t seem to have any control over what I eat anymore. My brain became addictive solo purposely to feed my stomach until it pops, I’m saddened that I had to admit. Good read.

  2. I don’t know. If my gut talks to my brain, it must be very quietly because I honestly do not notice any difference mentally whether I eat junk food or fresh veggies. My mood seems more affected by stress and sleep than anything else…

    1. I don’t notice changes in mood based on what I eat, either. It sounds like the mix of intestinal critters is impacted more by diet patterns over time rather than short term variation.

  3. My sis Sofi’s gut is very chatty from what I know from her, she very often says that she feels things in her gut or that her gut told her to do something, I don’t think I know anyone who has a closer and more matey relationship with her viscera than she does.
    As for me, I have a lot of gut feelings, but I think my brain and gut used to chat a lot more when I was younger. I used to have weird feelings inside as a child which I would describe as “feeling sad in my tummy”. My parents assumed it must simply mean that I’m hungry, but, although even I didn’t know what that actually meant, I’m pretty sure now that it was something more sophisticated than hunger as my brain would usually be a little blue at the same time too. What my brain and gut definitely must talk a lot about with each other is anxiety because usually the first anxiety symptom I feel when things are quite bad will be nausea, and I also eat a lot less when I’m really stressed.

  4. Stress and anxiety go straight to my stomach but I doubt it has anything to do with probiotics or whatever – that’s why people get ulcers – stress/anxiety seem to generate acid which eats big holes in your stomach – so possibly a different topic of conversation altogether?

  5. I hope my gut & brain aren’t chatting. I wouldn’t trust my gut at all, lying son of a bitch!

    I remember over my years of bowel issues pre-stoma investigating all sorts of things, and one was the gut microbiome. Good bacteria, bad bacteria, probiotics, probiotics. I’d found some stuff back then, at least 10yrs ago, that suggested the true importance of the gut bacteria balance was far underestimated and that it could impact general health as well as mental health. I think it was fairly basic though, more like an excess of bad bacteria could be linked to depression, so more common sense generalisations rather than tangible findings.

    You saying about serotonin production made me wonder though… When things like serotonin -among other things being produced or absorbed – happen in the gut, do they mean the small bowel or the large bowel? Am I all out of serotonin? That could explain a lot with my mental health. I think it’s too late to ask for my large bowel back 😂

    1. Interesting question. It looks like enterochromaffin cells are the major players, and they’re located throughout the intestinal tract but are more concentrated in the small intestine. So you’re probably okay with not asking them to hunt around and see if they’ve got your large bowel at the back of a closet somewhere. 😁

  6. As an adult we were diagnosed with a primary immune deficiency disease that is permanent. We were prescribed antibiotics twice per day for 9 months per year. We took probiotics at that time on and off. Our guy must’ve been f’ed up supremely.

    Finding out what foods were also making us sick regularly (bloated, irregular popping/diarrhea) and inflamed has helped us simply because there’s less suffering without those symptoms. For us, FODMAP seems in general to improve condition. We avoid especially onions, garlic, cherries, apples, pears, peapods, and also avoid cow milk and gluten.

    Not sure the direct link to brain but not surprised we’re f’ed up in both

      1. I don’t know if it’s genetic or a result of always consuming a lot of dairy, but luckily my gut seems to manage lactose without any difficulties.

        1. I think it’s genetic. I only became lactose intolerant at 30 and previously pretty much enjoyed regular cow’s milk with my coffee etc. Quite a big surprise for me to learn lactose intolerance is actually common. Supposedly up to 90% of Asians are but if you look practically anywhere in my country, it’s lots of cow’s milk and only limited lactose free cow’s milk or plant based milk.

  7. aguycalledbloke

    Now this is a great post Ashley, and one l have bookmarked for more depth reading later on tonight. I will come back to this.

  8. My gut and brain definitely chat. It shows up as IBS flares when I’m severely stressed. Even before that, I’d make jokes about “therapy shits” because it’s rather common due to anxiety!

    I try to eat healthy because anti-psychotics can affect cholesterol and blood glucose. The friend I live with says she’s now diabetic type 2 from both genetic predisposition and long term use of various anti-psychotics.

  9. There are several diseases which hapoen due to gut microbiome such as IBS which i turn affects mental health as well. It is viscious. Loved your content by the way. #mywordskraft

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