Gut-Brain Health – What Neuroscientists Are Calling “A Paradigm Shift”

paradigm shift

The trillions of microbes that inhabit your body are collectively called the microbiome.

They outnumber your own cells ten to one and weigh up to twice weight of the average human brain. Most of them live in your gut and intestines, where they help to digest food, synthesise vitamins and ward off infection.

The microbiome has shown that its influence extends far beyond the gut, all the way to the brain.

I’ve written about this in the blog before: One billions reasons probiotics protect your brain, and it looks like the gut-brain topic is hotting up with David Perlmutter author of Grain Brain set to publish a book in April: ‘Brain Maker – the power of gut microbes to heal and protect your brain – for life’. In Brain Maker, Dr. Perlmutter will explain

the potent interplay between intestinal microbes and the brain, describing how the microbiome develops from birth and evolves based on lifestyle choices, how it can become ‘sick’ and how nurturing gut health through a few easy strategies can alter your brain’s destiny for the better.

Not to be outdone, last November members of the Society for Neuroscience (SFN) held a symposium titled Gut Microbes and the Brain: Paradigm Shift in Neuroscience. A summary paper of emerging topics covered in the symposium has been published that claims that

“…the discovery and the explosive progress in the characterisation of the gut microbiome have initiated a paradigm shift in medicine and neuroscience.”

Here is a summary of the symposium discussions:

Gut-Brain signalling

A growing body of preclinical literature has demonstrated there is a complex signaling system between the mind, brain, gut, and its microbiome.

These findings have resulted in speculation that alterations in the gut microbiome may play a pathophysiological role in human brain diseases, including:

  • autism spectrum disorder
  • anxiety
  • depression
  • chronic pain.

John Cryan, the irish neuroscientist you met in my previous article, likens communication to Downton Abbey-like upstairs/downstairs communication,

“The upstairs and the downstairs need each other to survive. From a distance, it looks like they are living completely separate and they don’t have much to do with one another. But when things start going wrong downstairs that filters on upstairs. It’s the same with the gut and the brain. If there is something wrong with your microbiome, it’s going to filter on upstairs in the brain, too.”

The microbiome is impacted by stress

Psychological and physical stressors alter the composition and metabolism of the gut microbiota. And experimental changes to the gut microbiome can affect emotional behaviour and related brain systems.

For example, when mice are given antibiotics researchers see a decrease in BDNF (a key protein involved in neuronal plasticity and cognition) in the hippocampus (a region involved in emotion, learning and memory).

Tracy Bale, Professor of Neuroscience at the School of Veterinary Medicine at the University of Pennsylvania, and her team have found that stress-induced changes to a mother’s microbiome can be passed to the offspring which in turn might alter the way her baby’s brain develops.

In a recent interview with the Kavli Foundation Bale notes,

“There are key developmental windows when the brain is more vulnerable because it’s setting itself up to respond to the world around it.  So, if mom’s microbial ecosystem changes — due to infection, stress or diet, for example — her newborn’s gut microbiome will change too, and that can have a lifetime effect.”

A role for probiotics

A growing body of evidence from rodent studies further supports a role for probiotics. Bifidobacterium and Lactobacillus probiotic treatment shows beneficial effects on anxiety- and depression-like behaviour in rats and mice.

In one human study of chronic fatigue syndrome (another disorder of brain–body interaction) a randomised, double-blind, placebo-controlled trial of a Lactobacillus-containing probiotic decreased anxiety, but not depression symptoms, in the active treatment group. This study, published as a brief report, lacked detail in terms of the reported result and should be interpreted with caution according the SFN symposium attendees.

Probiotics being used widely (and represent a 20 billion dollar industry). Overall, human studies suggest a potential for positive effects on mood, but human work is preliminary and the SFN symposium called for larger, well-designed clinical trials to be conducted.

What’s next for gut-brain research?

Crowd-sourcing fecal samples (yep, The American Gut Project is crowd-sourcing poo!), fecal transplants, mRNA sequencing or proteomics, fMRI … the symposim concluded that it is difficult to predict the trajectory of the next exciting period of discovery.

Will the gut microbiome add paradigm-transforming insights to our existing understanding of human brain function in health and disease, resulting in novel therapies?

Or will it represent an incremental step in understanding the inner workings of our brains?

Certainly, the next few years of research hold the potential of  uncovering intriguing connections between gut bacteria and neurological conditions that may possibly impact human health.

Tim Cryan is very enthusiastic,

“We’re right at the dawn of a whole new way of thinking about brain development and brain heath. And the neuroscientific evidence for the role of the microbiome is just getting stronger and stronger at the basic level.”


Image source: Wikicommons

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  1. steve on March 9, 2015 at 10:37 am

    Very interesting article thanks! …. this might take you on a new direction 🙂

  2. Danielle on March 11, 2015 at 8:51 am

    Knowing the importance of the gut microbiome, I have been concerned about my new baby’s long-term health since she was born (she is 8.5 months old now). I was administered IV antibiotics for about 20 hours before she was born, which turned out to be via cesarean. I wish I had a better understanding of how to help restore/protect her gut so that she had an optimal chance of being healthy and strong!

    • Sarah McKay on March 12, 2015 at 1:56 pm

      Good question Danielle. Here is a link to an open-access review paper on this topic: I’m not medically qualified, so can’t offer on your little girl’s health. But don’t beat yourself up on her birth – there are plenty of other ways to promote healthy gut flora beyond the first moments of birth.

  3. DeusCat @ Brunswick Health on March 23, 2015 at 5:02 pm

    Nice referencing, you are the first blogger I’ve looked at this month to do this properly, beautiful article, thank you, definitely some food for thought there :3

    • Sarah McKay on March 23, 2015 at 5:12 pm

      That’s a nice comment 🙂 Thanks!

  4. Jacqueline Allen on March 30, 2015 at 10:29 pm

    Great article Sarah. There is a lot being written about gut health and brain fog but it’s more from the perspective of avoiding grains and dairy rather than micro biomes and probiotics. Poor gut health also affects the absorption of nutrients that impact wellness including mood. I don’t think we understand nearly enough on the whole inter-relation between the two but your article makes an excellent contribution to furthering our understanding

    • Sarah McKay on March 31, 2015 at 9:48 am

      Thanks so much Jacqueline – yep, there is more to good health than just giving up gluten 😉 Glad you found this helpful – I need to get my hands on Perlmutter’s book and see what he has to say.

  5. jan ejsymontt on July 28, 2015 at 11:52 pm

    Thank you Sarah, great article. Would you suggest taking probiotics in a tablet form?

  6. joan taylor on December 22, 2015 at 2:00 am

    Hi Sarah, I am currently taking an online course thru Warriors At Ease, regarding teaching trauma sensitive persons meditation which speaks to the effect of meditation/yoga on the brain. Thus I sent them off this link.
    I have always suspected the gut/brain connection, feeling the “brain fog” if I indulge in foods which one seems to crave when under stress. I learned that it is not only the amount of sugars, as I have learned how to indulge with out the sugar, it was associated when I felt a sense of “weakness” , lack of mental strength, and insecurity. Which promoted more of the same, a sabotage of myself, so failure was a way out. I am happy to see that , hopefully, with this knowledge I will use it to know and be able to focus on my gut. I have understood that when I am faced with a stress where my strength is threatened, and it is prolonged…5 more lbs pop up, even when my healthy diet has not changed. It takes quite awhile to calm down that “inner stress” in order for the gut to catch up to an effective mode of function.
    In yoga classes I encourage the focus to be on the “gut” or core, like the old saying:”You have to (get) or have guts” courage is effective when our gut is ineffective.

    Love your new avenue of focus, I hope the majority see’s the importance. Joan Taylor in Maine

  7. Sherry Wright on May 17, 2016 at 9:19 pm

    Thanks Sarah. An interesting article. Thank you. I have had a number of clients with severe anxiety and depression who have started to take yakult first thing in the morning….. Yogurt on their cereal/ as part of their lunch and dinner. They have reported a lot of improvement in their symptoms and overall health. They have continued with their medication as well and their overall sense of well being has improved markedly ( according to them)

  8. […] A growing body of research has demonstrated that a complex signaling system exists between the mind, brain, gut, and its microbiome which may play a role in brain conditions, including autism, anxiety, depression, and chronic pain. Maintaining a flourishing microbiome, which is wiped out by antibiotics, with probiotics (good bacteria) is showing promising results to improving everything from irritable bowel syndrome and oral health to mood, stress, and depression. Read more here about the enteric nervous system and about gut-brain health. […]

  9. […] So, so interesting … the gut, mind, brain link explained very clearly with speculation that alterations in the gut microbiome may play a role in human brain diseases such as anxiety and depression. Well worth the read. […]

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About Dr Sarah

I’m an Oxford University-educated neuroscientist, presenter of ABC Catalyst, director of The Neuroscience Academy, and author of The Women's Brain Book. The neuroscience of health, hormones and happiness.

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