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Brain, Gut and Behavior: Bacteria Matter

Cell structure of a bacterium, one of the two ...

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Mind and Body: New Evidence About Gut Bacteria and Brain Function

The science is there folks: gut physiology, gut bugs, healthy gut bugs make a difference in human behavior. Check out these several points:


There are between 2-4 pounds of bacteria in one’s [adult] intestinal tract. Scientists estimate that there are more bacterial cells in your gastrointestinal tract than the entire number of cells in the rest of your body.

There are two types of bacteria in our intestinal tracts:
there is beneficial bacteria and pathogenic or harmful bacteria. The ratio of beneficial to harmful bacteria is perhaps the most crucial element in our health today. Researchers estimate that the average intestinal tract of a healthy individual should be approximately 85% beneficial and 15% pathogenic. While that 15% pathogenic is still in your body, it is benign when it is in the presence of the 85% beneficial bacteria. The real problem here is that the average individual, consuming the standard American diet, has the exact opposite ratio, which is 15% beneficial and 85% pathogenic.”

From Crohn’ under Bacteria

Findings from Science Daily

ScienceDaily (May 17, 2011) — For the first time, researchers at McMaster University have conclusive evidence that bacteria residing in the gut influence brain chemistry and behaviour.

The findings are important because several common types of gastrointestinal disease, including irritable bowel syndrome, are frequently associated with anxiety or depression. In addition there has been speculation that some psychiatric disorders, such as late onset autism, may be associated with an abnormal bacterial content in the gut.

The research appears in the online edition of the journal Gastroenterology. – Working with healthy adult mice, the researchers showed that disrupting [decreasing] the normal bacterial content of the gut with antibiotics produced changes in behaviour; the mice became less cautious or anxious. This change was accompanied by an increase in brain-derived neurotrophic factor (BDNF – nerve growth factor), which has been linked to depression and anxiety. When oral antibiotics were discontinued, bacteria in the gut returned to normal. “This was accompanied by restoration of normal behaviour and brain chemistry,” Collins said.

Another Noteworthy Reference – Stress, Gut, Immune Dysfunction

ScienceDaily (Mar. 22, 2011) — Stress can change the balance of bacteria that naturally live in the gut, according to research published this month in the journal Brain, Behavior, and Immunity.

Exposure to stress led to changes in composition, diversity and number of gut microorganisms, according to scientists from The Ohio State University. The bacterial communities in the intestine became less diverse, and had greater numbers of potentially harmful bacteria, such as Clostridium.

“These changes can have profound implications for physiological function,” explained Dr Bailey. “When we reduced the number of bacteria in the intestines using antibiotics, we found that some of the effects of stress on the immune system were prevented,” he added. “This suggests that not only does stress change the bacteria levels in the gut, but that these alterations can, in turn, impact our immunity.”

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Just a few notes to keep you tracking on the bigger CorePsych picture ;-) Have a great week! – And do leave a comment it these findings impact your own life.

  1. I can absolutely attest to this theory, and especially the GI Repair system.

    During my initial treatment with Dr Parker, the period in which everything changed was once I started the GI Repair. Not exactly cheap, but it made a huge difference. Unfortunately an unexpected stressful situation reared it’s head and knocked me back on my bottom.

    Dr Parker – I suppose heavy stress would dramatically hinder gut functioning, maybe a second “repair” wouldn’t hurt?

    • Josh,
      You got it. Stress is one of the most important variables in gut physiology and healthy gut function. I don’t remember the details, but food allergies were also a problem, as they so often are, then that diet thing needs steady attention as well.

      Hope all is well, thanks for your feedback! At least you guys missed Sandy!

  2. It was back in the 80’s when I discovered, first hand, the brain gut connection observing my five year old eat milk products and then, depending on the setting and circumstances, turn into either a brazen hussy or possessed demon. It was Doris Rapp, MD and Lendon Smith, MD who helped with needed understanding and information regarding this behavior. One can view some outdated, yet still pertinent, videos re: children and food reactions on this website –-

    I had a wonderful vitamin cocktail, now long forgotten, recommended by Lendon Smith, that I would give my daughter before going to birthday parties. I exaggerate. It wasn’t a cocktail. I think it was vitamin B-6, Calcium and MG that worked like MAGIC to avert her swirling into the crazies. I mean…it was magic.

  3. For layers of peer reviewed evidence on behaviors and diet do take a look at and just for starters. You will have significant results if you simply look at the literature on just this antigen alone – If Columbia University is writing about it, if Johns Hopkins is concerned about these issues, just drive on over and look at those sites.

  4. Where do we stand in terms of peer reviewed, statistically meaningful studies in terms of 1) baseline behaivors and diet. 2) Wheat and milk elimination and measurable impacts versus comparisons to baseline and standards, and 3) probiotic treatments and measurable improvement in mood, behaivor, and cognitive abilities (reading, math, focus on tasks).  Thanks

  5. Kb,
    First find any challenges with IgG levels, as food immunity issues are quite simply the most common challenges that effect the proliferation of bad gut bacteria, and interfere with the growth of healthy gut bacteria.

    Specific probiotic interventions make a remarkable difference once the offending immunity issues are addressed. We have found considerable positive response with this probiotic system available at the CoreBrain Store:

    And if a person wants to only address less pervasive problems this smaller, less complicated probiotic intervention often proves helpful:


  6. Awesome information, thank you! My question would be what steps can we take to correct the imbalance? 

  7. fascinating to know that “gut feeling” may be actually reliable. :)

    Connie Myers

    • Yes, Connie, but that feeling part is almost always associated with IgE reactions rather than the chronic and stealthy IgG which often don’t produce palpable sensory responses.

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