How Are Your Brain and Gut Connected?

by Alejandra "Alex" Ruani — Get free science updates here.

New discoveries show that the trillions of bacteria in your gut have a powerful influence on your behaviour, your memory, and even your decision making.

But how exactly do gut microbes shape our brains and our behaviours?

Grab “How are your brain and gut connected?” below:


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Conveniently download this 35-page science report. Contains links to extra reading materials and scientific references.

Topics covered in this report:

  1. That gut feeling
  2. What’s the gut microbiome?
  3. The gut-brain link
  4. Your gut and the stress response
  5. Response to stressors
  6. But how is this linked to the brain?
  7. When reckless mice attract predators
  8. Gut microbes and brain development
  9. What are the biological mechanisms?
  10. LPS, peptidoglycans and cytokines
  11. Cytokines, cortisol and inflammation
  12. Low mood, anxiety and bad memory
  13. Neurological conditions
  14. Graphic: The gut-brain axis
  15. Production of neurotoxins
  16. The D-lactate hypothesis
  17. Neuroendocrine mechanisms
  18. Probiotics and better mood
  19. Emotion, behaviour, appetite and more
  20. Your key takeaways
  21. Learn more
  22. References and resources


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If you want to get the latest science and our tips, make sure you sign up to our Thursday emails HERE.

And I'd love to hear from you in the comments below:

  1. What's your number one discovery from this report?
  2. What does it mean to you and those you help?
  3. Are there any action steps you would take, or things you would change as a result of this report?

Share your own insights with me and your fellow readers!

Alex Ruani leads the research division at The Health Sciences Academy, where she and her team make sense of complex scientific literature and translate it into easy-to-understand practical concepts for students. She is a Harvard-trained scientific researcher who specialises in cravings and appetite neurobiology, nutrition biochemistry, and nutrigenomics. Besides investigating and teaching the latest advances in health and nutrition science, Alex makes it easier to be smarter with her free Science Catch-ups every other Thursday.
Connect with Alex via email.

Every other Thursday we share our research and actionable advice to help you and those you care about. If you enjoyed this, join our FREE updates.


  • Susan, nutrition coach

    Reply Reply March 19, 2015

    I love getting these emails with the attachments, they are always a great read. I have a lot of clients with digestive issues and this is really helpful
    keep um coming :0)

    • Alex

      Reply Reply March 19, 2015

      Susan – thanks for your lovely feedback! Our ultimate goal is helping you help others with your new insights :-)

  • Sam Metson

    Reply Reply March 19, 2015

    I really enjoy reading the Thursday morning reports. Wouldn’t it be great if they landed in every doctor’s inbox on a Thursday too! This would help slash the national drugs bill and of course these drugs are a main cause of gut microbe disruption. Is there an affordable test that identifies the main types and balance of your microbes and if you have leaky gut? I believe I read in Datis Kharrazian’s excellent book “Why Isn’t My Brain Working” that the gut/blood barrier and blood/brain barrier are very similar in structure and so when one is damaged, so might the other be. If the brain barrier is damaged, it sets off microglia cells in a frenzy of autoimmune attack. This is bound to effect mental processes and behaviour at some point, as microglia cells destroy neurones, which they out-number by a factor of 10 times. Your nutrition, your intestinal barrier health and your microbes are the foundation of good health or the cause of ill health, depending upon your choices and exposures Gut function assessment should be the starting point for virtually any chronic disease. Even children’s learning and emotional problems are heavily influenced by gut health and yet this message is hardly been spread at all.

    Anyway, Alex, thanks again for another stimulating report.

    • Alex

      Reply Reply March 19, 2015

      You’re so welcome, Sam!

  • Sally Thompson

    Reply Reply March 19, 2015

    Amazing report, Alex and team!

    Are my decisions really mine … or are they “theirs” (microbes)? It makes you wonder, doesn’t it? Their survival is dependent on ours. I like the erratic mice example.

    It gives me goose-pans to think about it, that my body is like an ecosystem with different species cohabiting it and interacting with each other and (OMG) with my brain!

    Thanks for opening my mind to these fascinating discoveries!!!!


    • Alex

      Reply Reply March 19, 2015

      Sally – indeed, lots to think about! Some say that Darwin got it all wrong when he proposed “the survival of the fittest” theory – microbial interaction examples show us that in the end it could well be the survival of the “most cooperative”

      • Eli

        Reply Reply March 20, 2015

        1) I like the part that talks about the gut as the second brain, that’s something totally new to me.. and how many neurons it has, with the microbes transmitting messages to the brain.. incredible!

        2) I’ll be looking at incorporating more probiotics in my diet, at the moment I don’t think I’m doing a good job with that to be honest!

        3) I’ll be telling my sister about this report, she’ll enjoy the brain development bit because of my little niece!

        Thank you for the Thursday reports, they are awesome!!!

        • Alex

          Reply Reply March 20, 2015

          Eli – nice summary of your takeaways, I’m all about you taking action for yourself and your loved ones! And yes, those microbial messages travelling to your brain are very powerful indeed :-)

  • Diana C

    Reply Reply March 20, 2015

    Hi Alex

    I love reading these reports, very informative and right on topic as well as timely.

    I have moved to Paleo and see such a connection with mind and gut issues due to how we eat and what we eat. I moderate a large Facebook group that is grain, sugar and dairy free and this information is so needed.

    Thank you.

    • Alex

      Reply Reply March 20, 2015

      Diana – thanks for your lovely feedback! My goal is for you to get smarter about these things whilst keeping an open mind :-)

  • David

    Reply Reply March 20, 2015

    So Alex, do you recommend pro-biotic supplements or fermented foods like Kimchi and sauerkraut? Any suggestions on repairing leaky gut such as glutamine or cabbage juice? Thanks for the great report. It confirms information in a fifteen year old book “The Second Brain” by Michael Gershon M.D.

    • Alex

      Reply Reply March 20, 2015

      David – you’re so welcome! Because the term ‘leaky gut’ is somehow controversial and interpreted in different ways by different people who associate it with different symptoms or view it as a condition on its own (which is not, as we’ve seen here:, I prefer to use the concept of ‘gut hyperpermeability’ – and not because I’m pedantic (by now you should know that I’m not :-)) but just to make sure we’re talking about the same thing, in the same context. By the way, thanks for the good questions, we’ll add them as new topic ideas for a future report so we can cover everything in more detail for you :-)

  • Lisa

    Reply Reply March 22, 2015

    Truly amazing!!!

  • Laura S

    Reply Reply March 23, 2015

    This is so cool! ~THANK YOU!!!

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