The Power of the Gut-Brain Connection


Whenever someone who doesn’t know me quizzes me about what I do, I often find myself talking to a person’s raised eyebrows. As I explain that I’m a journalist who researches the connection between our mind, body and health, I usually find that I’m met with skepticism at best and cynicism at worst. Since releasing my film about the subject, I’ve met countless others working in this space who experience the same frustration. In a world full of quackery, it can be hard to cut through with real science. Over the years I’ve developed a few ‘go-to’ examples of the new science of the mind body connection to explain what I’m on about and for this blog post I thought I’d share one of them.


In 1899 two English scientists named William Bayliss and Ernest Starling were studying the gut of an anaesthetised dog when they made an intriguing observation. The physiologists had been working together to study the movements and contractions in the digestive tract, which moved food from one place to another. They had called this effect the ‘law of the intestine’ and believed that nerves were responsible for coordinating this automatic function. What was interesting in the particular dog they were studying was that when they cut communication between the gut and the central nervous system, their ‘law of the intestine’ still prevailed. In other words, Bayliss and Starling had discovered that the gut can still perform its duties if it’s not talking to the brain.


Unfortunately the world would more or less forget about the discovery of this independently functioning nervous system for a hundred years or so and we continued along as though the brain was an all mighty dictator of bodily function and the single determinate of all things emotional. But in 1998 Michael Gershon, a Professor at Columbia University published a landmark book called The Second Brain: Your Gut Has a Mind of Its Own and the game changed.


The book was part memoir and part detailed explanation of Gershon’s discovery of the neurochemistry of what he called the second brain. The book’s publication and Gershon’s subsequent appearances on television talk shows and in mainstream magazine feature articles finally gave the remarkable second brain the notoriety it deserved. Gershon is regarded as the father of the field now known as neurogastroenterology.


Through the work of Gershon and others, we have come to understand that deep within our gut walls lies an enteric nervous system which can not only talk to our brain, but it also has the ability to act independently and can influence our behavior. In fact, about 90 percent of the signals passing along the nerve that connects your brain to your gut come not from above, but from the second brain below. Although you are not conscious of your second brain thinking and it is unlikely to ever write a sonnet or invent a rocket ship, a compelling body of research is demonstrating that the second brain has a good deal of influence on our every day lives.


I’ve written before about the second brain’s influence on our mood after my own experience of the hangries – when hunger and anger combine to create a potentially lethal combination. It turns out this is partly because our gut-brain produces a hormone called ghrelin (or as I like to call it, gremlin) to tell the brain in your head to eat something, fast.


This week I was intrigued to come across more research, which further illustrates the power this second brain has over our mood. The study led by Lukas Van Oudenhove at the University of Leuven, Belgium asked a dozen healthy people to fast for 12 hours before they were injected with either saline solution or a fatty acid solution directly into their stomach.   For the next 30 minutes, the researchers played them classical music and showed them emotive images on a screen while observing what happened in their brains as they lay under an FMRI scanner. They found that people given the fatty acid injection reacted less strongly to sadness. In fact their emotional responses were almost half that of the people given the saline injection. Though the study was small, it’s interesting that the results are on par with the effects of pharmacological antidepressants on mood scores. The study may explain why some of us reach for particular comfort foods during time of emotional upheaval and is another significant step towards explaining the relationship between our brain and gut as bi-directional. The brain talks to the gut and the gut talks back.


I’ve spent the last few years diving deep into the latest research demonstrating the link between our mind and body and am still stunned by the emerging evidence on the second brain in our gut. I thoroughly enjoy having conversations with the uninitiated and love watching the source of their raised eyebrows turn from skepticism to surprise and even intrigue. Given that this is just one example of the latest science proving mind body connection though, you might want to make sure you have some time on your hands before you get me started on the subject of evidence based mind body medicine.

  • purisity

    25 years ago when I was diagnosed with M.E. I followed the advice of Claire Francis , the British Yachtswoman turned novelist who herself had been diagnosed with M.E. some years earlier. I changed my diet. Unsurprisingly for me it dramatically affected my symptoms.The 'brain fog' cleared, muscle aches weren't as painful,headaches improved and energy levels returned. At the time , the inference from doctors was that I had either' decided to pull myself together' or it was' only a matter of time before I'start to improve anyway.I was also meditation/praying/pacing. Since that time I have had 3 relapses- every one relates to times of extreme stress with little time for meditation and significantly reverting back to eating the way I did before I became ill- the typical 'western' high carbohydrate diet/diary/sweet things etc.
    To maintain good health, the gut is the starting point.It is crucial to include good bacteria in your healthy diet -prebiotics,probiotics,good fats and oils – as well as nutritional fresh food- in particular, artichokes , asparagus, potato salad(!) sauerkraut , beetroot – the list can go on – all play their part in healthy body /healthy mind. However the study in this area is still in its infancy. Before we all run to buy these probiotics etc -a good introductory read of the bestseller GUT by Giulia Enders helps to get you started.She concludes it is crucial to keep the gut healthy. Good Bacteria keeps the bad in check. Good bacteria produces vitamins in our gut and eats the bad.
    If the good and bad are kept in equilibrium – you 'll have less of the 'hangries'!

  • Luana Bricco

    Five months ago I was diagnosed with colon cancer and had two-thirds of my colon removed. (The surgery was very successful). The cancer was stage II so I did not require chemo or radiation. Since the surgery I have had memory problems and sometimes feel as though I am experiencing "brain fog" which seems to be similar to what I hear cancer patients who receive chemotherapy talk about. It is very disconcerting. I was sick for almost a year before my diagnosis and I find that my memory of events for about six months before my surgery are also sketchy. I also had a very severe episode of depression 6 months before the surgery, and a milder episode about 6 weeks after the surgery. I am doing fine now, except for the memory problems, such as forgetting the names of people I work with, and some procedures that I have performed for years, but have to mentally review before completing. I have read some research that correlates these symptoms with colon removal, one study done by Johns Hopkins, I have talked with my doctors about this but they do not address my concerns and just say that I should give myself more time in recovery. I am very interested in any research that may be ongoing, or that has been published, on the correlation of memory loss and depression after colon removal. It would be very helpful to patients who have colon removal to understand the possibilities, or help to learn if there is any remedial treatment after colon removal for depressive episodes and memory problems.

  • Ted

    Years ago, when my daughter was suffering from symptoms of Irritable Bowel Syndrome (IBS), I came down with a case of sympathetic pain (my description). I would wake up in the middle of the night with a sharp pain in my stomach and would have to get up and pace and burp until I felt better. Then, I bought a CD with meditation specifically for IBS (initially for my daughter, but I listened too). I listened to it a few times and my symptoms went away. Every once in a while, if I get a nervous stomach ache, I visualize dumping the pain into a deep well. And it still works!

    What this tells me is that there is a two-way conversation between the brain in my head and the brain in my gut. So, I wonder how I can tap into this conversation at an intuitive level and learn to let both brains synch up and improve my health.

  • Marie

    This is so true in2003 I had my first bowel resection due to Crohns and I had to completely retrain myself on my lectures thought I had a stroke during the op was never told about this but have always said my guts have a mind of their own.

  • Luana Bricco

    Did the condition improve over time?

  • Shannon

    Thanks for sharing this fascinating story. The worry-gut link is one I'll write about more in the future. There is some really interesting research that ties in nicely with your experience.

  • Shannon

    Thanks for sharing your story Luana. I can only imagine how difficult this must be but I'm pleased to hear that you are doing ok.

    You might want to check out this review study called "Enteric nervous system neuropathy: repair and restoration" which may offer some insights. –

    Also, this paper from 2013 may be of interest –

    This paper also explore gut-brain restoration in guinea pigs. FYI the 5-HT4R the scientists are referring to is serotonin –

  • Shannon

    It's so interesting that you had to discover all this for yourself and that you weren't pointed in this direction by professionals. I'm looking forward to reading Giulia Ender's book shortly, and am currently engrossed in The Diet Myth by Tim Spector, who also takes a microbial view of diet to explore what we should and shouldn't be eating. Thanks for writing a little about your experience.

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  • Amanda Allen

    You are not the only one who loves to study the gut and brain connection. So excited to read your article if you have a moment maybe you can contact me. I would be interested in discussing this on a upcoming radio show. My email is [email protected] Thanks Amanda

About the author: Shannon Harvey

Shannon Harvey is a journalist and producer who was diagnosed with an autoimmune disease when she was 24 years old. Although doctors meant well, none could offer her a cause or a cure. Since then Shannon has been researching the latest scientific research linking her mind and body to health outcomes. Nearly 10 years have passed since her diagnosis and today Shannon is well and not taking medication. Shannon has worked as a television, radio and online journalist and producer and has a Master’s degree in Communications. She worked for the ABC and Fairfax before starting her own production company, Elemental Media. Shannon is the director of the feature film The Connection.



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