The Brain-Gut Connection: A Q&A with Dr. Emeran Mayer

(Editor’s note: This article from the Fall 2016 issue of Brain World magazineIf you enjoy this article, consider a print or digital subscription!)


BW: You did some research with native groups in Latin America — could you speak about that?

EM: During medical school, I had the opportunity to participate in several documentary film expeditions to South America and Irian Jaya, Indonesia. One of the most interesting expeditions related to the topic of the gut microbiota was the trip to the Yanomamis, a prehistoric tribe living on the Orinoco River, on the border between Venezuela and Brazil. Almost 40 years later, when I attended a big microbiome conference in Washington D.C., one of the presenters — Maria Gloria Dominguez and her group — showed pictures and data from the same Mayer cont’d will really burn anything, which is available at any given time, assuring our survival in an ever-changing world.

So if no meat is available it runs perfectly on just some plant-based food. If a lot of meat, animal fat, and refine carbohydrates are available like now in Western societies, the system tries to adapt to this situation as well, even though with unintended negative consequences to our health. But when I looked around which modern diet the hunter-gatherer diet of the Yanomami diet relates to, I found the Mediterranean diet in some ways very close to that.

A high percentage of complex carbohydrates from plants, a low percentage of animal fat, and a moderate amount of animal protein. There are now many large-scaled controlled studies clearly showing several health benefits associated with the Mediterranean diet in terms of breast cancer, colon cancer, and even brain disorders. So it seems that we can learn a lesson from the dietary habits of the prehistoric hunter-gatherers, and we don’t have to adapt one of the constantly evolving fat diets.

One can speculate that amongst other factors, the high diversity of gut microbes that people on these diets have has an important health benefit. That it’s protective against many of the diseases we see now in Europe and North America.

BW: Is how we digest and how the body processes food somehow related to the brain-gut connection?

EM: That’s a really important concept. Your gut is kind of like your facial expression. When you’re angry, you can look into somebody’s face and tell instantaneously his or her emotional state, simply based on the pattern of activity of the facial muscles.

A similar thing happens at the gut level — the contractions, secretions, the blood flow, sensitivity — all change all the time in response to your emotional state, just like your face changes; the only differences is that nobody can see it. When food comes in, it is processed very differently, depending on your emotional condition. We now know that the gut microbes are also affected by this brain-gut communication. For example, stress can influence the composition and the metabolites that the microbes produce. My view on this is that if you are in an unbalanced or unhealthy emotional state, not only your gut but also your microbes are very different, and that will affect then what happens when you feed them.

If somebody eats when they’re depressed they may gain weight faster than somebody who’s not depressed. Remember, that your gut is not just a simple food processing and waste storage facility — it’s functions closely reflect your state of mind and your emotions and it is perfectly equipped to fulfill these special functions: The enteric nervous system alone has between 50 and 100 million neurons, and the gut contains specialized cells that can produce hormones — 40 different hormones and peptides that are being released when we eat. One class of these specialized cells contains 95 percent of your body’s serotonin, a signaling molecule that has a big influence on your mood, sleep, appetite, and overall well-being. So the gut is not just a digestive organ, but a complicated, essential component of our emotional system.

BW: I always wonder if paying more attention and focus can help the condition of the gut because you’re putting your mind fully to it?

EM: There are many studies that show that focusing your mind on the gut can be beneficial for treating symptoms of IBS or other stress-related digestive symptoms. Our group has just finished a study in patients with IBS who undergo mindfulness-based stress reduction, and we look at the brain and the microbes and the symptoms before and after the intervention. We are testing the hypothesis that IBS patients will get better with these exercises, and you can detect this beneficial effect both at the brain level and also at the gut microbiome level. We are doing a similar study using cognitive behavioral therapy, an intervention which aims to change your thoughts and reactions to external (stress) and internal (gut sensations) events.

Another important unanswered question is related to the effect of diet on the brain. For example, if individuals go from vegan to a meat-based diet and you use sensitive instruments to assess feeling and cognitive states could you see changes solely triggered by dietary changes. There’s a lot of interest now in such studies on mind-brain-gut microbiome studies, much more than 10 or 20 years ago

BW: Could you recommend one thing everyone should know about this mind-gut connection that would be useful?

EM: I think just realizing the important of the mind-brain-gut connection is step one. Step two is that you can actually influence the interactions within this system significantly by choosing the right lifestyles.

One is that everything you put inside of you, how you benefit from that, has to do with your mind state. And everything you put in will influence how you feel. In simple terms, this interdependency is reflected in the term “healthy food, healthy mind.” There clearly is also an important role of regular exercise in influencing brain-gut microbiome interactions. We know that regular exercise has a beneficial effect on the brain, and can reduce stress responsiveness, and research suggests that people who exercise a lot have a different microbiome composition. These findings indicate that regular exercise exerts its beneficial effect in part through modulation of the brain-gut microbiome interactions.


In my book I mention that people have to become their own ecosystem engineers. In other words, they have to learn to understand the concept of the mind-brain-gut microbiome interactions. With this basic understanding you can chose lifestyles and foods which increase the diversity of the gut microbiome and increase resilience of brain-gut microbiome interactions. I think in our society we’re obviously doing a lot of things that are entirely against this principle. We eat when we’re stressed, we eat without any awareness of what we eat and what it may do to our gut-brain axis — the whole fast food thing. And we eat food that is totally altered from the food our system has evolved to process optimally.

(Editor’s note: This article from the Fall 2016 issue of Brain World magazineIf you enjoy this article, consider a print or digital subscription!)

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