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Dr. Emeran Mayer

The Gut & Brain Connection and Ending Inflammation


My guest today is Dr. Emeran Meyer, one of the world’s foremost experts on the gut-brain connection. For the past 40 years, his research has provided groundbreaking evidence of the critical connection between the brain and the gut. He’s written a new book called The Gut-Immune Connection: How Understanding the Connection Between Food and Immunity Can Help Us Regain Our Health.

Our conversation was so powerful that I decided to break it up into two different parts. In part one, we discuss the biggest triggers for inflammation, the foods we should eat and avoid to improve our gut health, why we’ve become so addicted to sugar, whether our brain or gut health affects our body more, how our digestive system functions, and so much more. Now, in part two, we go even deeper and learn some actionable takeaways that could change your life. Once you read this post, be sure to listen to the episode — there’s so much info in it we just couldn’t fit in here, so you’ll have to listen to get it all! 

Who is Dr. Emeran Mayer?

Dr. Emeran Mayer is one of the top gut-brain-connection experts in the world — and with more than 40 years experience researching this connection, you could even say he’s a pioneer. He draws on the latest science, including his own research, to show the link between changes in our diet, the gut microbiome, gut health, and the increased prevalence of many chronic diseases like diabetes, heart disease, and cancer, as well as susceptibility to infectious diseases like Covid-19. Dr. Mayer makes a strong case for the interconnectedness between all organs and the microbes in our bodies, and between the prominent role of the food we eat (including how it’s grown) in altering these connections. 

In his new book, Dr. Mayer proposes a radical paradigm shift, in which he puts the gut microbiome and the gut-based immune system at the center of the current epidemic of chronic non-infectious diseases. He’s the executive director of the GE Oppenheimer Center for Neurobiology of Stress and Resilience and the co-director of the Digestive Disease Research Center at the University of California, Los Angeles.

Dr. Mayer’s research has been supported by the National Institutes of Health for the past 25 years.

Let’s jump right in!

What is the “Gut” Made of?

Before we get into the specifics about what our gut does and how it influences our lives and body, let’s define exactly what Dr. Mayer means when he uses the term gut. 

When he first began medical school, it was believed that the gut’s only function was as a digestive organ tasked with breaking food down into components that provide nutrients for the body. The entire system included the esophagus, the stomach, the small intestine, and the large intestine, each with its own job in the breakdown process.

However, it was while Dr. Meyer was researching with the late John Walsh that this definition began to change.

“There were molecules in the gut that somewhat didn’t fit that description.  There were newer neurotransmitters from the brain to the gut and some receptors. People thought, ‘Why is that?’ It was the discovery of a nervous system in the gut — 150 million neurons that are there in several layers. … The main function of that system is really to completely regulate the gut in an animal model. You can take out the gut, put it in a test tube, and the gut will still have the same functions.” – Dr. Emeran Mayer

Dr. Mayer believes that the first marine creatures in the oceans began to develop from single-cell organisms where there was only a gut, and slowly developed to have a head too. The theory is that some of these nerves migrated to the head and formed the beginning of the central nervous system. 

“Later, our big brains took over the regulation in response to the environment and the coordination of organs within the body, and the digestive side was left to the brain in the gut nervous system. But that means there’s a very intimate relationship between these two. Clearly, the heart gets a lot of signals from the brain when we’re stressed, or the blood pressure goes up, but it’s nothing compared to what goes on in this multi-lane highway between the brain and the gut.” – Dr. Emeran Mayer

Dr. Mayer believes this multi-lane highway between our gut and brain is why we have so many emotions linked to our gut. 

We know the gut is responsible for digesting food but does the food directly impact our gut too?

Impact of Food on Our Gut

The idea that a healthy diet — one filled with whole foods and very few processed carbohydrates and sugars — is required for a healthy body and healthy life isn’t news. With that in mind, I was curious what Dr. Meyer’s research has revealed about the impact sugar and processed foods might be having on our gut-brain relationship. Here’s what he said: 

“The short-term effect [comes from] a lot of receptors in our mouth, like sweet tastes or bitter taste receptors that also sense texture. The brain gets this immediately and forms memories of this, and your sweet preference is programmed early on in life. We do this extensively with our kids for any positive event, like birthdays or celebrations, [with] lots of sugar.” – Dr. Emeran Mayer

In other words, one of the most obvious ways we can see our gut-brain connection in action is in our relationship to processed sugar — starting all the way back in childhood, when most of us are introduced to sugar for the first time! That introduction, which might seem like it only involves our taste buds, actually creates new neural connections in our brains that can make our consumption of sugar harder to moderate later in life.

Speaking of moderation, the gut-brain relationship can even explain why so many of us still consistently make the same food choices every single day — even when they make us feel tired, lethargic, unfocused, and just plain terrible:

“[The other effect] is the adaptive mechanisms where sugar and fat change the receptors and desensitize the Vagus nerve [which] generates a feeling of satiety and fullness. If you’re on a high-fat diet, these receptors get desensitized and you no longer get that feeling, so you keep eating because the feedback mechanism that shuts off is no longer [working]. Our diet with these high-caloric, high-density foods has hijacked the system.” – Dr. Emeran Mayer

It’s fascinating to learn how certain foods can actually switch off the mechanism in our brains that tell us we’re full and don’t need anymore. We overeat these dense, processed foods until we’re too tired to focus on our personal goals or on making better choices. These foods, which make us feel good and happy while we’re eating them, ultimately end up making us more depressed. They can even play a role in neurodegenerative diseases like Alzheimer’s and Parkinson’s.  

So what foods does Dr. Mayer recommend?

“We need to refocus our diet on feeding the optimal food to our microbes.” @emeranamayer  

The Best Foods for a Health Gut-Brain Relationship

I always enjoy asking doctors from various specialties what their top foods are that they would choose if they could eat nothing else. Naturally, Dr. Mayer chose foods he says are the best if you’re looking to optimize your gut-brain relationship — and we should be!

His picks aren’t surprising either: they’re whole, natural, and plant-based, with a healthy fat or two, like seeds or nuts, thrown in for good measure.  

“The majority fall into the category of plant-based foods: leafy vegetables, roots, seeds, nuts, and a big variety of these foods. You [can’t] just eat tomatoes or just kale and nothing else, it won’t give you that benefit. We should refocus our diet on feeding the microbes.” – Dr. Emeran Mayer

 For some of us, knowing what we should eat is easy — it’s knowing what to enjoy in moderation that’s a bit harder. Not only that, but according to Dr. Mayer, some of the best foods for us can be laden with dangerous chemicals. So what can he teach us about the negative impact some foods can have on our gut-brain relationship?

To Nourish Your Gut, Moderate or Avoid These Foods 

When it comes to optimizing our health, it’s not just about finding what is best for our digestive system, but also what negatively impacts it. While things like moderating sugar and processed carbs might seem obvious, Dr. Mayer says there’s a bit more to it than that.

“The number one [detriment to gut health] is the standard American diet, which has deficiencies in all the components that are essential for a healthy microbiome, and ultimately for a healthy gut barrier. There are other things like toxins that come with food and chemicals. Even if you’re a vegetarian, if you don’t pay attention to where your food comes from, you may be absorbing a lot of stuff [like] herbicides, pesticides, or insecticides…” – Dr. Emeran Mayer

When discussing pesticides and herbicides, Dr. Mayer pointed out soy in particular, explaining that while soybeans are a very healthy source of fiber and protein, if farmers use Roundup and other dangerous chemicals to destroy pests among their soy crops, then when we eat that soy, those chemicals can actually kill some specific and critical microbes in our guts.

He also pointed to the central valley in California, which currently has an epidemic of Parkinson’s disease. Vegetables in the central valley are produced in an industrial agricultural style with Roundup. Interestingly, people seem to worry more about genetically engineered food (GMOs), but evidence suggests it’s the chemicals — not the genetic engineering — that’s actually contributing to Parkinson’s in the area. 

“It’s an epidemic in that area. A colleague of mine at UCLA studies that population, and all the people are exposed [to the chemicals when] these crop dusters fly over. It’s [in] the air, probably in the water as well. These foods have, on the surface, residues of increasing amounts of chemicals that are being sprayed on them, and the kind of washing that you do at home doesn’t work.” – Dr. Emeran Mayer

When the chemicals have been used for decades, they become part of the soil, and thereby absorbed as part of the food that grows in that environment. This is why, even if you are a vegetarian or vegan, it’s not just about the food you choose to eat, but the quality of the food.

Why You Should Listen to This Dr. Emeran Mayer Podcast Episode Right Now…

Guys, this is part one of our fascinating conversation with Dr. Emeran Mayer. We highly recommend listening to the full episode to get all of Dr. Mayer’s wisdom, and don’t forget to share it with your friends! You can head over to part two to hear the rest of our discussion where Dr. Mayer gives us guidance on how to get the mind and body working together at the highest level in order to achieve your full potential. Not only that, but Dr. Mayer helps us put it into practice.

I highly recommend learning more about Dr. Mayer’s new book on his website, or you can follow him on Instagram

If you enjoyed this conversation, please make sure to spread the message of greatness and inspire someone else in your life. It would be really great if you could also tag Dr. Mayer, @emeranmayer, and me, @lewis howes, on Instagram with a screenshot of this episode and your greatest takeaways from it.

I want to leave you with this quote from Julius Erving who said, “If you don’t do what’s best for your body, you’re the one who comes up on the short end.” Optimizing your health is all about seeking wisdom, and transforming that wisdom into daily practice. The gut and brain connection is real, so be sure to check back in for part two to learn more! 

If no one’s told you lately, I want to remind you that you are loved, you are worthy, and you matter. It’s time to go out there and do something great. 

To Greatness,

Lewis Howes - Signature

“Any emotions that you experience have a mirror image in your body.” @emeranamayer  

Some Questions I Ask:

  • Which has more influence on the body, the brain or the gut?
  • What does a scarcity mindset do to your immune system?
  • How do we heal the memory that develops in our cells?
  • How do we process information in the brain?
  • What are the foods that we should be eating to help the body & gut connection?
  • What are the main things that destroy the gut?

In this episode, you will learn:

  • The biggest triggers for inflammation.
  • The foods we should eat & avoid to improve our gut health.
  • Why we’ve become so addicted to sugar & the effects it has on our body.
  • Whether our brain or gut health affects our body more.
  • How our digestive system functions.
  • And so much more…
Dr. Emeran Mayer & Lewis Howes
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Dr. Emeran Mayer

Transcript of this Episode

Music Credits:


Kaibu by Killercats

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