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Book Summary: The Mind-Gut Connection – How the Hidden Conversation Within Our Bodies Impacts Our Mood, Our Choices, and Our Overall Health

The Mind-Gut Connection (2016) explores the complex relationship between the gut and brain, highlighting the crucial role this connection plays in both physical and mental health. The book delves into key insights, such as the brain-gut axis, the impact of stress on gut health, and the connection between food and mental well-being, emphasizing the need for holistic care to improve overall health.

Introduction: Manage your emotions differently by understanding how your gut affects everything

Have you ever wondered why your stomach churns when you’re nervous or why a hearty meal can bring you comfort after a tough day? It all comes down to the astounding relationship between your gut and your brain.

Just imagine: nestled within your gut are trillions of microscopic organisms, all bustling with life – and they’re not just helping you digest food. They’re chatting with your brain, influencing your mood, thoughts, and feelings. But, as it turns out, the conversation is two-way. Yes, your brain has something to say, too!

In the following summary, you’ll discover how your diet, stress levels, and even your social connections can affect this bustling micro-world within you. And you’ll get an idea of how to improve and even repair your brain-gut communications so you can enjoy better all-around well-being.

So, strap in and get ready to change the way you view your gut, your brain, and perhaps your health overall.

Book Summary: The Mind-Gut Connection - How the Hidden Conversation Within Our Bodies Impacts Our Mood, Our Choices, and Our Overall Health

Royal enemas, etc.

The earliest writings of ancient humankind contain references to enemas. In Ancient Egypt, the pharaoh had a “keeper of the rectum” who managed all of his enemas. Ancient Babylonian and Assyrian tablets mention the use of enemas as early as 600 BC. Susrut, the father of Indian surgery, wrote details of implements he used to clean out the colon.

Why has humanity been obsessed with the state of the human gut for so long? The answer may lie in a quote credited to Hippocrates: “All disease begins in the gut.”

It turns out that Hippocrates wasn’t too far off in his thinking. We now know that immune cells located throughout the gut make up the largest part of the immune system. Not only that – the gut is equipped with its own dedicated nervous system that many people refer to as a second brain. And, as if that weren’t enough, the gut contains endocrine cells that hold 20 kinds of hormones and also contains the largest supply of serotonin in your body.

These systems don’t just hang out in the gut independently of the rest of the body. They communicate with the brain via the vagus nerve. So if you’ve ever had a “gut feeling” about something, that phrase is more than just a metaphor. You probably had a literal gut feeling.

Using this vagus nerve super highway, your brain receives tons of information from your gut every day, and stores that information in memories. Studies suggest that you’ll never be consciously aware of about 90 percent of that information, but it can and does affect how you behave in response to certain stimuli. Research has also found that 90 percent of the information transferred goes from gut to brain, and only ten percent from brain to gut. Think of the gut like an agent in the field sending intelligence back to head office.

So with all of this information at hand, it’s no wonder that researchers are speculating about the possibility of the gut’s role in the development of mental and emotional conditions like depression and anxiety.

In 1822, army surgeon Dr. William Beaumont was able to witness firsthand, in a bizarre way, the direct effect that emotions have on digestion. He treated a man named Alexis St. Martin, who had been accidentally shot through the stomach with a musket.

While Dr. Beaumont was able to help St. Martin regain function, he wasn’t able to permanently close up his stomach. As a result, there remained enough access to the stomach so that Dr. Beaumont could actually observe digestion in real time. With the consent of St. Martin, Dr. Beaumont studied the direct effects of emotional stimuli on digestive responses.

As the experiments were often uncomfortable for St. Martin, he frequently became upset during the process. By watching St. Martin’s gastric activity as his mood turned, Dr. Beaumont found that St. Martin’s anger ended up slowing his digestion.

While Beaumont’s experiments showed how feelings affect digestion, later experiments showed how gut microbes affect behaviors. Scientists transplanted fecal microbes from one mouse into another and observed any changes in behavior. They found that a timid mouse injected with the microbes of an extroverted mouse became more extroverted. And a lean mouse injected with the microbes of an obese mouse changed its eating habits and gained weight.

This opens up a whole realm of speculation on the role gut microbes play in your feelings and behaviors, and what possibilities there may be in the future for gut-based therapies.

Funny feelings in your gut

In 1983, a Soviet Air Defense Forces officer named Stanislav Petrov received a system alert that five missiles were heading toward the Soviet Union from the United States. Faced with the potential of an all-out nuclear war, Petrov opted not to take any action.

Of course, as it turned out, the warning was a false alarm, but Petrov didn’t truly know that at the time. When asked why he didn’t alert someone or launch retaliatory missiles, the officer gave several reasons, but during a later interview, he explained that he simply had a gut feeling.

Humanity has intuitively known for centuries that a connection exists between what you eat and how you think. Take the example of Ebenezer Scrooge from the 1845 novel A Christmas Carol. Scrooge sees a ghost and attributes the vision to something he ate that night.

Now, we’ve finally got science explaining these direct connections among the brain, body, and gut. In the rest of this section we’ll discuss how the gut responds to stress and how it interacts with the brain to shape the way you feel and behave.

If you’ve ever been given a bit of bad news or been startled by a loud noise, then you know how stress feels in your gut. Actual physiological responses occur in your body when stress occurs. And when stress is chronic, those physiological responses can send our systems into disarray.

One study of 54,000 children and teens who had experienced traumatic or chronically stressful events in their youth showed that they were more likely to suffer from conditions like heart attack, asthma, stroke, or diabetes later in life.

What’s interesting is that stress may have affected you long before you were born. Studies confirm that there is a close relationship between a mother’s stress levels during pregnancy and the way your nervous system reacts to stress now. So stress is actually transferable from generation to generation, and it all comes down to our microbiomes.

Babies in the womb don’t have their own gut microbiome yet. However, as they are born, they carry the seeds of that microbiome from the microbes in their mothers’ vaginas. As there is a link between the type and quality of microbes in your system and the way you react to stress, this transfer explains one way in which stress responses can become hereditary.

Now, let’s get back to that “gut feeling” mentioned at the beginning of this section. Knowing what we know about the effects microbes have on chemical production in the body and signals to the brain, and knowing how we can inherit our microbiomes, we can start drawing some inferences as to what all this means in our decision-making processes.

Regarding the question of whether to trust our gut feelings, the answer given to us by evolution is the prefrontal cortex – the part of our brain that has the ability to override ancient systems when those systems appear to be incorrect.

Your gut is always sending information to your brain. Your brain stores this information in a subconscious memory library. When you encounter various moments in life, your brain manifests a reaction in the form of feelings. Those feelings may line up nicely with an event. For instance, you come home and your child runs up to you and you feel happy. On the other hand, if your child ran up to you and you felt panic, you would need to consciously override that feeling in order to respond appropriately.

The point of all this is that while your brain has access to a bottomless pool of wisdom that has existed in your body from the point of birth, it isn’t always right. So should you trust your gut? You should definitely listen to it, but you should also apply higher reasoning.

Get superhealthy

Only five percent of the North American population qualifies as superhealthy, meaning they are living in a state of optimal health in all areas of life, including physically, emotionally, spiritually, and more.

When you learn how the odds are stacked against you, it’s not surprising that the number is so low.

First of all, let’s talk about the North American diet. It’s high in animal fats, mostly due to fried and processed foods, as well as high-sugar-content foods. It is designed for speed and convenience so we can keep moving through our high-stress days without having to stop for food.

We already know that stress negatively affects the balance of your microbiome. We also know that the North American diet contributes to lifestyle disorders and diseases like obesity, high blood pressure, and diabetes. In fact, the majority of Americans who haven’t been diagnosed with an illness are living in a pre-disease state with all the conditions in place to eventually develop serious illness.

The simple answer here might seem that we should analyze those super healthy humans and try to duplicate their microbiomes in order to achieve optimal health for everyone. We’ve learned that microbiota can be transplanted. However, we also know that while humans share 90 percent genetic similarity, they often only share about five percent microbiome similarity. Because diversity is important, the answer to better health should be more about optimizing your existing microbiome.

In addition to all of that, there is one important fact proven by research that raises the bar on our goal of optimal health. Studies have shown that the same high-fat, sugary American diet that contributes to disease also actually reduces stress and depression levels.

As a result, it almost seems like you only have two choices: be healthy and stressed, or sick and happy.

To understand why those bad-for-you foods may reduce your stress level, let’s talk about cats and rats.

Cats carry a parasite called toxoplasma gondii. This parasite can be found in cat feces. It’s passed to rats when the rats try to dig undigested food out of the feces. The cats then eat the rats, and that’s the life cycle of toxoplasma. But there’s actually more to it than that.

It wouldn’t make sense for a parasite to try to stay alive using an animal that runs from the parasite’s original host. So the parasite hijacks the rat’s brain and causes it to become sexually attracted to the smell of cat urine. The rat willingly seeks out cats, making it easy for a cat to capture it – and for the parasite to continue its existence.

Now, the scientific speculation mentioned earlier is about the idea of our microbiome and our dopamine-rewards system. We know that fatty, sugary “comfort foods” reward us with reduced stress and happy feelings at the expense of our overall health. Some scientists speculate that certain microorganisms in our gut could be hijacking our dopamine-reward system to get the food they need at the cost of the health of the host – us.

This isn’t proven by any means, but it’s within the realm of possibility and is being investigated.

So with so much stacked against us – including our bodies’ responses to food, both negative and positive – how can we be healthier? Remember that we have the adaptive trait of the prefrontal cortex that gives us the power of choice. That’s what it’s going to take to restore your body to optimal health. Here are a few rules to follow.

  1. Treat your body like a farm and actively choose to nurture your microbiome.
  2. Reduce fried, fatty, and processed foods.
  3. Eat foods that have been fermented, like sauerkraut and yogurt.
  4. Make a rule that you won’t eat in response to feeling stressed, angry, or sad.
  5. If you’re pregnant, practice proper nutrition and try to keep your stress levels at a minimum.
  6. Fast regularly to give your gut a chance to restore itself.
  7. Make mealtime a social time. The positivity from interacting with people you love will improve your gut’s response to food.

Many of these rules are things you’ve likely heard before. Unfortunately, there’s no magic trick to being healthy – there’s only conscious choice in the matters of food. But now you know the complex biological reasons why you may be suffering from poor health – and why these dietary rules are vital.


A human being functions more like an ecosystem than a machine. The more we learn about that ecosystem and the trillions of microbes living within it, the more we realize how important diet is to literally everything about life – from our physical health, to our emotional responses, to the way we behave in different situations.

And it’s a two-way street. Emotions can affect digestion, too. The organisms living in the gut communicate directly with the brain via a complex nerve system known as the “second brain.” Knowing this, we can now begin to understand how we are what we eat and how our emotions are shaped by the microbial response to stimuli within our gut. And finally, we’ve learned that the dietary wisdom we know so well, such as the advice to avoid processed foods and eat at the family table, are actually vital to our health.

By understanding and nurturing the complex relationship between our gut and brain, we can unlock the potential for improved health, happiness, and overall well-being.

About the author

Emeran Mayer, MD, has studied brain-body interactions for the last forty years. He is the executive director of the G. Oppenheimer Center for Neurobiology of Stress and Resilience and the codirector of the Digestive Diseases Research Center at the University of California at Los Angeles. His research has been supported by the National Institutes of Health for the past twenty-five years, and he is considered a pioneer and world leader in the area of brain-gut microbiome interactions.


Psychology, Science, Health, Nutrition, Nonfiction, Self Help, Food, Medicine, Biology, Body Care, Technology, Gastroenterology, Cognitive Neuroscience and Neuropsychology

Table of Contents

Preface ix
Part 1 Our Body, the Intelligent Supercomputer
Chapter 1 The Mind-Body Connection Is Real 3
Chapter 2 How the Mind Communicates with the Gut 29
Chapter 3 How Your Gut Talks to Your Brain 51
Chapter 4 Microbe-Speak: A Key Component of the Gut-Brain Dialogue 75
Part 2 Intuition and Gut Feelings
Chapter 5 Unhealthy Memories: The Effects of Early Life Experiences on the Gut-Brain Dialogue 107
Chapter 6 A New Understanding of Emotions 137
Chapter 7 Understanding Intuitive Decision Making 167
Part 3 How to Optimize Brain-Gut Health
Chapter 8 The Role of Food: Lessons from Hunter-Gatherers 197
Chapter 9 The Onslaught of the North American Diet: What Evolution Did Not Foresee 225
Chapter 10 The Simple Road Toward Wellness and Optimal Health 263
Acknowledgments 291
Bibliography 293
Index 307


Combining cutting-edge neuroscience with the latest discoveries on the human microbiome, a practical guide in the tradition of Wheat Belly and Grain Brain that conclusively demonstrates the inextricable, biological link between mind and body.

We have all experienced the connection between our mind and our gut—the decision we made because it “felt right”; the butterflies in our stomach before a big meeting; the anxious stomach rumbling when we’re stressed out. While the dialogue between the gut and the brain has been recognized by ancient healing traditions, including Ayurvedic and Chinese medicine, Western medicine has failed to appreciate the complexity of how the brain, gut, and more recently, the microbiome—the microorganisms that live inside us—communicate with one another. In The Mind-Gut Connection, Dr. Emeran Mayer, executive director of the UCLA Center for Neurobiology of Stress, offers a revolutionary look at this developing science, teaching us how to harness the power of the mind-gut connection to take charge of our health.

The Mind-Gut Connection shows how to keep the brain-gut communication clear and balanced to:

  • heal the gut by focusing on a plant-based diet
  • balance the microbiome by consuming fermented foods and probiotics, fasting, and cutting out sugar and processed foods
  • promote weight loss by detoxifying and creating healthy digestion and maximum nutrient absorption
  • boost immunity and prevent the onset of neurological diseases such as Parkinson’s and Alzheimer’s
  • generate a happier mindset and reduce fatigue, moodiness, anxiety, and depression
  • prevent and heal GI disorders such as leaky gut syndrome, food sensitivities and allergies, and IBS, as well as digestive discomfort such as heartburn and bloating
  • and much more.

* * * * *

Chances are, at some point in your life you’ve noticed the connection between your brain and your gut. If you’ve ever felt queasy as you walked into an uncomfortable situation or based a life decision based on a “gut feeling,” then you know that sometimes our bodies react faster than our minds. Most of us have also experienced the same phenomenon in reverse, where our mental state has affected our digestive system—like the butterflies in our stomach before an important meeting or a first date. But while the dialogue between the mind and the gut has been recognized for centuries, scientists today are just starting to understand how powerful that connection is.

In The Mind-Gut Connection, Dr. Emeran Mayer, executive director of the UCLA Oppenheimer Center for the Neurobiology of Stress, offers a cutting-edge view into this developing science, showing us the full impact of how the brain, gut, and microbiome—the community of microorganisms that live inside the digestive tract—communicate. As Dr. Mayer explains, when this communication channel is out of whack, major health problems can crop up, including food sensitivities and allergies, digestive disorders, obesity, depression, anxiety, and fatigue.

The Mind-Gut Connection teaches us how, with a few simple changes to our diet and lifestyle, we can enjoy a happier mindset, enhanced immunity, a decreased risk of developing neurological diseases such as Parkinson’s and Alzheimer’s, and even lose weight. With a simple, practical regimen drawn from the latest research, Dr. Mayer shows us that paying attention to the mind-gut balance is the key to unlocking vibrant health.


“The Mind-Gut Connection presents the incredibly humbling reality that our very perception and interpretation of the world around us is virtually dictated by the microbes living within us. This book redefines what it means to be healthy and eloquently provides the means to manifest that goal.” — David Perlmutter, MD, author of the #1 New York Times bestseller Grain Brain and Brain Maker

“Drawing on his vast experience as a practicing gastroenterologist, Dr. Mayer writes about the connections that our brains have with our guts, especially with the microbes that make the gut their home. Describing a rapidly advancing realm of knowledge, this thoughtful guide provides practical advice to improve health.” — Martin J. Blaser, MD, author of Missing Microbes

“Dr. Emeran Mayer elucidates the intricate biochemical dialogue that occurs between the brain, digestive tract, and trillions of bacteria residing in the gut. He dubs this form of communication ‘microbe-speak’ and speculates on its implications for social behavior, decision making, emotional wellbeing, and maybe mental health.” — Booklist

“After a long period of neglect the enteric nervous system has been recognized as the ‘second brain’. Dr. Emeran Mayer, a true expert of this topic, has now written the best lay-public guide yet to this spectacular part of ourselves. Recommended reading.” — Antonio Demasio, author of Descartes’ Error, The Feeling of What Happens, and The Self Comes to Mind

“I have known Emeran Mayer for years and have learned to pay attention to what he says and writes. The Mind-Gut Connection is a delight. Both scholarly and fun to read, I highly recommend it to anyone interested in learning more about how the mind and gut communicate.” — Michael D. Gershon, MD, author of The Second Brain

“Microbiome research is revolutionizing our understanding of the human body and the brain. In The Mind-Gut Connection, Dr. Emeran Mayer provides authoritative insight into this rapidly expanding field. Synthesizing recent research with patient stories and personal anecdotes, he offers practical, evidence-based recommendations to keep the dialogue between the brain, the gut, and its microbes flowing smoothly.” — Rob Knight, PhD, author of Follow Your Gut and director of the Center for Microbiome Innovation, UC San Diego

“The Mind-Gut Connection is a revolutionary new holistic view of what keeps us healthy, ranging from the food choices we make to the ways we can train our mind, with the ultimate goal of attaining optimal health. ” — Kenneth R. Pelletier, PhD, MD, Clincal Professor of Medicine and Professor of Public Health, University of California School of Medicine (UCSF)

“Microbiome research is revolutionizing our understanding of the human body and the brain. In The Mind-Gut Connection, Dr. Emeran Mayer provides authoritative insight into this rapidly expanding field. Synthesizing recent research with patient stories and personal anecdotes, he offers practical, evidence-based recommendations to keep the dialogue between the brain, the gut, and its microbes flowing smoothly.” — SELF online

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