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

255 Pages·2018·2.17 MB·English

by  Emeran Mayer

Dedication
To Minou and Dylan
for their persistent encouragement to
listen to my gut feelings.
To my mentor, John H. Walsh,
who kindled my interest in gut-brain communications.
Contents
Cover
Title Page
Dedication
Preface
Part 1
Our Body, the Intelligent Supercomputer
Chapter 1: The Mind-Body Connection Is Real
Chapter 2: How the Mind Communicates with the Gut
Chapter 3: How Your Gut Talks to Your Brain
Chapter 4: Microbe-Speak: A Key Component of the Gut-Brain Dialogue
Part 2
Intuition and Gut Feelings
Chapter 5: Unhealthy Memories: The Effects of Early Life Experiences on the
Gut-Brain Dialogue
Chapter 6: A New Understanding of Emotions
Chapter 7: Understanding Intuitive Decision Making
Part 3
How to Optimize Brain–Gut Health
Chapter 8: The Role of Food: Lessons from Hunter-Gatherers
Chapter 9: The Onslaught of the North American Diet: What Evolution Did Not
Foresee
Chapter 10: The Simple Road Toward Wellness and Optimal Health
Acknowledgments
Bibliography
Index
About the Author
Praise
Copyright
About the Publisher
Preface
S
ince the initial publication of The Mind-Gut Connection in the summer of
2016, I have talked to many audiences large and small, to the lay public and to
academics across America and Europe, on the topic of brain-gut interactions and
how our gut health impacts our overall mental and physical health. I’ve also met
one-on-one with many readers interested in learning more about how this
emerging science can improve their overall well-being and, for some, their daily
quality of life.
Many of these individuals were patients who recognized their own or their
child’s symptoms in the stories I share in the book. Some were seeking advice
on how best to harness the recent insights into the microbiome to alleviate
digestive symptoms, improve their anxiety or depression, or slow the
progression of neurological diseases such as Parkinson’s. Others were executives
from the burgeoning biotech industry or the food industry looking for guidance
on how to tailor their products to promote microbiome health.
These experiences have convinced me that the so-called “brain-gut-
microbiome axis” and its impact on our mood and our health has become a hot
topic. Every day more and more scientific literature offers evidence that
disturbances of brain-gut interaction have implications for a wide array of health
issues, from conditions like food sensitivities and functional GI disorders to
psychiatric disorders like depression and food addiction to brain disorders like
autism spectrum disorders, Alzheimer’s disease, and Parkinson’s disease. While
some of these ideas and hypotheses about specific brain disorders remain
speculative, a few are now supported by well-designed studies in human
subjects.
For example, in the short amount of time since the The Mind-Gut Connection
was published, four studies have been published that have clearly linked an
alteration in gut microbial composition in patients with chronic depression.
However, it is important to keep in mind that the majority of published human
studies so far have only demonstrated associations between alterations in gut
microbial composition and specific diagnoses, without proving a causal
relationship. In other words, we don’t know if the observed changes in the gut
microbiome in these diseases are a cause of the respective disease or a
consequence of the underlying brain disorder, altered disease-related dietary
patterns, or medication use. But it’s clear that there is a connection between the
microbiome and cognitive function. Well-designed research is now underway to
determine possible causality and to identify novel targets for the treatment of
common brain disorders.
Of the various aspects of the brain-gut microbiome communication
addressed in The Mind-Gut Connection, I receive the most feedback and
questions on the topic of nutrition. It wasn’t until I started having conversations
with readers that I realized how challenging it has become for health-minded
people to determine which foods are right for them. Given the array of food
information and diets available—many with contradictory messages—how can
one decide what eating style is best? There is an ever-growing number of books
and websites promoting these conflicting messages supposedly based on the
latest scientific evidence, and often these messages are linked to online shopping
sites for food supplements, including pre-and probiotics. How should a health-
conscious person decide if it is better to consume a mix of ten (“carefully
selected”) different probiotic strains (as recommended on various websites) and
if it is important to buy a probiotic with more than 40 billion CFU (colony-
forming units)? Despite the information provided online, including Amazon
reviews (the majority of which are paid advertisements), surprisingly there is
currently no scientific evidence to prove the great majority of these claims. If the
confused patient turns to his or her doctor for advice, he or she will likely be
disappointed. The majority of healthcare providers are neither on top of the
rapidly progressing science of the microbiome, nor trained in giving evidence-
based nutritional advice.
By focusing on the detrimental effects of the modern North American diet in
The Mind-Gut Connection, it became obvious to me that a diet that is high in
plant-based complex carbohydrates (from a large variety of different plants),
plant-derived fat, grains, naturally fermented foods, and fish, and low in red
meat, animal-derived fat, refined sugars, and processed food is the blueprint for
most healthy diets around the world. Even better, if you add the benefits of
polyphenols (molecules with health-promoting effects that are largely processed
by the gut microbiota) contained in olive oil and red wine, certain plant products
with anti-inflammatory effects such as turmeric, curcumin, and ginger, and a
large number of fermented foods teeming with microorganisms, you have a
simple road map for a diet that is good for your microbes (increases the
diversity, abundance, and populations of health-promoting microbes), good for
your gut (reduces intestinal permeability, e.g., improves a leaky gut), and good
for your brain (prevents low-grade immune activation in your brain). While as a
scientist, I rarely give up my professional skepticism toward new health benefit
claims of any treatment, in the case of dietary and lifestyle recommendations
based on the new brain-gut microbiome science, I am willing to drop my
skepticism and unconditionally endorse such a way of eating.
In The Mind-Gut Connection, I focused on the Mediterranean diet as an
example of an eating style with significant evidence-based health benefit for us
and our gut microbes. Based on this growing scientific evidence, studies are now
underway evaluating the benefits of the Mediterranean diet for slowing the
progression of Alzheimer’s and Parkinson’s disease, or for the improved
pharmacologic treatment of depression. Such studies would have been
unthinkable and unfundable even ten years ago, before the science of the
microbiome became available.
While I have focused on the example of the Mediterranean diet in this book,
it is certainly not the only diet that is associated with gut and brain health
benefits. Most traditional diets all around the world share a similar composition
to the Mediterranean diet, even though the individual ingredients may vary
depending on the respective geographic region. Traditional Asian diets, for
example, including the Japanese, Korean, and Chinese diets, share a high
consumption of fish, varied plant-based foods rich in polyphenols and
antioxidants, grains, and naturally fermented foods, and limited meat and dairy
products. In addition, traditional food consumption in these Asian cultures as
well as in Mediterranean countries has a strong communal element, including the
sharing of multiple small dishes during a meal.
During a trip to Korea in the fall of 2016, I learned that the traditional
Korean diet consisted, to a large degree, of plant-based dishes, fish, and poultry
with a moderate amount of red meat and very little animal-based fat. And then
there was the eye-opening experience of seeing the numerous fermented foods
that accompanied the main dish; for every meal, there was an astonishing
number and variety of so-called fermented banchan, kimchi, and kimchi soup.
After three days of enjoying these traditional Korean dishes, including up to
thirty different types of banchan along with rice and soup, I started to wonder
how many live microorganisms the average Koreans must ingest every year
starting from infancy, a period that is particularly critical for the formation of a
healthy microbiome and the brain-gut axis.
In Japan, a traditional meal may consist of a bowl of miso soup, a bowl of
rice, some fish, and several vegetable dishes—cooked, fried, or pickled—all
served on small plates. This way of eating and often sharing multiple, small
portions resembles the way Koreans eat their fermented banchan and people in
Spain enjoy their tapas. Another important element of the Japanese cuisine is the
mindfulness that goes both into the artful preparation of the meal and its
consumption. Traditional food in Japan is not something that is consumed while
driving in the car or watching TV, and it is not valued based on its quantity or
macronutrient composition. As I experienced during my visits to Japan, eating a
Japanese meal fully engages one’s attention, appealing to all the senses,
including visual appeal, texture, and taste.
The benefits for longevity, cardiovascular health, and brain health of the
traditional Japanese diet are well established. An increase in the prevalence of
typical Western diseases such as obesity, metabolic syndrome, and Alzheimer’s
disease has significantly increased in Japanese living in the United States,
approximating rates seen in non-Japanese Americans. But also for Japanese not
living in the United States, the prevalence of dementia has increased over the last
few decades. Proposed mechanisms to explain this phenomenon in Japan include
the gradual shift away from fish and mainly plant-based foods to a higher
consumption of meat and animal products. Data suggests that one dietary factor
most strongly associated with the rise in Alzheimer’s disease in Japan is the
increased consumption of animal fat.
There are other populations around the world which illustrate the negative
impact on people’s health when shifting from a largely plant-based diet to the
North American diet. Well-documented population studies on dietary habits and
chronic disease exist to show the detrimental effect of these dietary shifts on the
metabolic and brain health of Hawaiians, Native Americans, and indigenous
populations in Central America.
It is intriguing to speculate, even though not proven at this point, that the
health benefits of the Japanese diet and other traditional diets around the world
have something to do with their positive influence on the composition and
diversity of the gut microbiota. As I discuss extensively in this book, plant-based
diets are associated with a healthier gut microbiome, and with a greatly reduced
risk for low-grade inflammation throughout the body, including the brain. I
strongly believe that the health benefits of the traditional Japanese diet, including
the Okinawan diet, are to a significant degree a consequence of an optimal
regulation of the interactions between diet, the gut microbiome, and the gut.
I hope that the reader will find this book helpful not only in gaining a better
understanding of the ways in which the brain, gut, and microbiome communicate
with each other in health and disease but also in making more rational and
science-based decisions about what to eat to stay well. While it will take a long
time before we fully understand the complexities of the gut microbiome and its
interactions with our brain, the simple recommendations in this book can be