The Mind-Gut Connection

Emeran Mayer

• Publisher: Harper Wave
• Year: 2016
• ISBN:
  9780062376596
• Topic: Medizin
• Subtopic: Ernährung, Diätetik & Bariatrie

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.

PART 1

OUR BODY, THE INTELLIGENT SUPERCOMPUTER

CHAPTER

1

THE MIND-BODY CONNECTION IS REAL

When I started medical school in 1970, doctors looked at the human body as a complicated machine with a finite number of independent parts. On average, it functioned for about seventy-five years, provided you took care of it and fed it the right fuel. Like a high-quality car, it ran well, provided that it didn’t have any major accidents, and that no parts were irreversibly compromised or broken. A few routine checkups during a lifetime were all you were expected to do to prevent any unexpected calamities. Medicine and surgery provided powerful tools to fix acute problems, such as infections, accidental injuries, or heart disease.

However, over the past forty to fifty years, something fundamental has gone wrong with our health, and the old model no longer seems to be able to provide an explanation or a solution of how to fix the problems. What’s happening can no longer be easily explained simply by a single malfunctioning organ or gene. Instead, we are beginning to realize that the complex regulatory mechanisms that help our bodies and brains adapt to our rapidly changing environment are in turn being impacted by our changing lifestyles. These mechanisms do not operate independently, but as parts of a whole. They regulate our food intake, metabolism and body weight, our immune system, and the development and health of our brains. We are just beginning to realize that the gut, the microbes living in it—the gut microbiota—and the signaling molecules that they produce from their vast number of genes—the microbiome—constitute one of the major components of these regulatory systems.

In this book, I will offer a revolutionary new look at how the brain, the gut, and the trillions of microorganisms living in the gut communicate with each other. In particular, I will focus on the role these connections play in maintaining the health of our brain and our gut. I will discuss the negative consequences on the health of these two organs when their cross talk is disturbed, and propose ways of how to obtain optimal health by reestablishing and optimizing brain-gut communications.

Even in medical school, the traditional, prevailing approach did not sit quite right with me. Despite all the studying of organ systems and disease mechanisms, I was surprised that there rarely was any mention of the brain and its possible involvement in such common diseases as stomach ulcers, hypertension, or chronic pain. In addition, I had seen a number of patients during rounds in the hospital for whom even the most thorough diagnostic investigations failed to reveal a cause of their symptoms. These symptoms mostly had to do with chronic pain experienced in different areas of the body: in the belly, the pelvic area, and the chest. So, in my third year of medical school, when it was time to begin my dissertation, I wanted to study the biology of how the brain interacted with the body, in the hope that I would develop a better understanding of many of these common diseases. Over a period of several months, I approached several professors from different specialties. “Mr. Mayer,” said Professor Karl, a senior internal medicine professor at my university, “we all know that the psyche plays an important role in chronic disease. But there is no scientific way today that we can study this clinical phenomenon, and there is certainly no way that you can write a whole dissertation on it.”

Professor Karl’s disease model, and that of the entire medical system, worked extremely well for certain acute diseases—diseases that come on suddenly, don’t last long, or both—in infections, heart attacks, or surgical emergencies like an inflamed appendix. Based on these successes, modern medicine had grown confident. There was hardly an infectious disease left that couldn’t be cured by ever-more-powerful antibiotics. Newly developed surgical techniques could prevent and cure many diseases. Broken parts could be removed or replaced. We only needed to figure out all the minute engineering details that made the individual parts of this machine function. Depending more and more on newly evolving technologies, our health care system promoted a pervasive optimism that even the most deadly of chronic health problems, including the scourge of cancer, could be solved eventually.

When President Richard Nixon signed into law the National Cancer Act of 1971, Western medicine acquired a new dimension and a new military metaphor. Cancer became a national enemy, and the human body became a battleground. On that battleground, physicians took a scorched-earth approach to rid the body of disease, using toxic chemicals, deadly radiation, and surgical interventions to attack cancer cells with increasing force. Medicine was already using a similar strategy successfully to combat infectious diseases, unleashing broad-spectrum antibiotics—antibiotics that can kill or cripple many species of bacteria—to wipe out disease-causing bacteria. In both cases, as long as victory could be achieved, collateral damage became an acceptable risk.

For decades, the mechanistic, militaristic disease model set the agenda for medical research: As long as you could fix the affected machine part, we thought, the problem would be solved; there was no need to understand its ultimate cause. This philosophy led to high-blood-pressure treatments that use beta blockers and calcium antagonists to block aberrant signals from the brain to the heart and blood vessels, and proton pump inhibitors that treat gastric ulcers and heartburn by suppressing the stomach’s excessive acid production. Medicine and science never paid much attention to the malfunction of the brain that was the primary cause of all these problems. Sometimes the initial approach failed, in which case even more intense efforts were used as a last resort. If the proton pump inhibitor didn’t quell the ulcer, you could always cut the entire vagus nerve, the essential bundle of nerve fibers that connects brain and gut.

There is no question that some of these approaches have been remarkably successful, and for years there did not seem to be any need for the medical system and the pharmaceutical industry to change their approach; nor was there much pressure on the patient to prevent the development of the problem in the first place. In particular, there didn’t seem to be a need to consider the prominent role of the brain and the distinct signals it sends to the body during stress or negative mind states. The initial remedies for high blood pressure, heart disease, and gastric ulcers were gradually replaced by far more effective treatments that saved lives, reduced suffering, and made the pharmaceutical industry wealthy.

But today, the old mechanistic metaphors are beginning to yield. The machines of forty years ago on which the traditional disease model was based—the cars, ships, and airplanes—had none of the sophisticated computers that play a central role in today’s machines. Even the Apollo rockets going to the moon had only rudimentary computing devices on board, millions of times less powerful than an iPhone and more comparable to a Texas Instruments calculator from the 1980s! Not surprisingly, the mechanistic disease models of the day did not include computing power, or intelligence. In other words, they did not consider the brain.

Paralleling the change in technology, the models we use to conceptualize the human body have also changed. Computing power has grown exponentially; cars have become mobile computers on wheels that sense and regulate their parts to ensure proper function, and soon they will drive without human input. Meanwhile, the old fascination with mechanics and engines has given way to a new fascination with information gathering and processing. The machine model was useful in medicine for treating some diseases. But when it comes to understanding chronic diseases of the body and the brain, it’s no longer serving us.

The Price Tag of the Machine Model

The traditional view of disease as a breakdown of individual parts of a complex mechanical device that can be fixed by medications or surgery has spawned a continuously growing health care industry. Since 1970, the per capita expense for health care in the United States has increased by more than 2,000 percent. Nearly 20 percent of all goods produced by the U.S. economy per year are required to pay for this enormous undertaking.

But while the World Health Organization, in a landmark report published in 2000, ranked the U.S. health care system as the highest in cost, it ranked it a disappointing 37th in overall performance, and 72nd by overall level of health among 191 member nations included in the study. The United States didn’t fare much better in a more recent report by the Commonwealth Fund, which ranked the U.S. health care system as the most expensive per capita among eleven Western countries, about two times higher than all the other surveyed countries. At the same time, the United States came in last in overall performance. This data reflects the hard fact that despite the ever-increasing amount of resources spent on dealing with our nation’s health problems, we have made little progress in treating chronic pain conditions, brain-gut disorders such as irritable bowel syndrome (IBS), or mental illnesses such as clinical depression, anxiety, or neurodegenerative disorders. Are we failing because our models for understanding the human body are outdated? There are a growing number of integrative health experts, functional medicine practitioners, and even traditional scientists who would agree with this assumption. But change is on the horizon.

The Mysterious Decline in Our Health

The failure to deal effectively with many chronic diseases, including irritable bowel syndrome, chronic pain, and depression, is not the only shortcoming of the traditional, disease-based model of medicine. Since the 1970s, we have also been witnessing new challenges to our health, including the rapid rise of obesity and related metabolic disorders, autoimmune disorders such as inflammatory bowel diseases, asthma, and allergies, and diseases of the developing and the aging brain, such as autism, Alzheimer’s, and Parkinson’s disease.

For example, the rate of obesity in the United States has progressively increased from 13 percent of the population in 1972 to 35 percent in 2012. Today 154.7 million American adults are overweight or obese, including 17 percent of American children ages 2 to 19, or 1 in every 6 American children. At least 2.8 million people each year die as a result of being overweight or obese. Globally, 44 percent of diabetes, 23 percent of ischemic heart disease, and 7-41 percent of certain cancers are attributable to overweight and obesity. If the obesity epidemic continues unabated, the costs of treating people suffering from obesity-related diseases are projected to increase to a staggering $620 billion annually

We are still grappling for answers to explain the sudden rise of many of these new health problems, and for most of them, we don’t yet have effective solutions. While the increase in our longevity in the United States has paralleled that of many other countries in the developed world, we are far behind in terms of physical and mental well-being when we reach the last decades of our lives. The price we pay for an increase in the quantity of years we live is a decrease in the quality of those years.

In view of these challenges, it’s time to update our prevailing model of the human body to understand how it really works, how to keep it running optimally, and how to fix it safely and effectively when something goes wrong. We can no longer tolerate the price tag and the long-term collateral damage that our outdated model has produced.

Until now, we have largely ignored the critical role of two of the most complex and crucial systems in our bodies when it comes to maintaining our overall health: the gut (the digestive system) and the brain (the nervous system). The mind-body connection is far from a myth; it is a biological fact, and an essential link to understand when it comes to our whole body health.

The Supercomputer View of Our Digestive System

For decades, our understanding of the digestive system was based on the machine model of the entire body. It viewed the gut mostly as an old-fashioned device that functioned according to principles of the nineteenth-century steam engine. We ate, chewed and swallowed our food, then our stomach broke it down with mechanical grinding forces assisted by concentrated hydrochloric acid before dumping the homogenized food paste into the small intestine, which absorbed calories and nutrients and sent the undigested food into the large intestine, which disposed of what remained by excreting it. This industrial-age metaphor was easy to grasp, and it influenced generations of doctors, including today’s gastroenterologists and surgeons. According to this view, the digestive tract’s malfunctioning parts can easily be bypassed or removed, and it can be dramatically rewired to promote weight loss. We have become so skilled in doing these interventions that they can even be performed through an endoscope without surgery.

But as it turns out, this model is overly simplistic. While medicine continues to view the digestive system as being largely independent of the brain, we now know that these two organs are intricately connected with each other, an insight reflected in the concept of a gut-brain axis. Based on this concept, our digestive system is much more delicate, complex, and powerful than we once assumed. Recent studies suggest that in close interactions with its resident microbes, the gut can influence our basic emotions, our pain sensitivity, and our social interactions, and even guide many of our decisions—and not just those about our food preferences and meal sizes. Validating the popular expression of “gut-based” decision making in neurobiological terms, the complex communication between the gut and the brain plays a role when we make some of our most important life decisions.

The connection between our gut and our mind is not something that solely psychologists should be interested in; it is not just in our heads. The connection is hardwired in the form of anatomical connections between the brain and the gut, and facilitated by biological communication signals carried throughout the bloodstream. But before we get too far, let’s take a step back and take a closer look at just what I mean by the “gut”—your digestive system, which is far more complex than a simple food processing machine.

Your gut has capabilities that surpass all your other organs and even rival your brain. It has its own nervous system, known in scientific literature as the enteric nervous system, or ENS, and often referred to in the media as the “second brain.” This second brain is made up of 50-100 million nerve cells, as many as are contained in your spinal cord.

The immune cells residing in your gut make up the largest component of your body’s immune system; in other words, there are more immune cells living in the wall of your gut than circulating in the blood or residing in your bone marrow. And there is a good reason for the massing of these cells in this particular location, which is exposed to many potentially lethal microorganisms contained in what we eat. The gut-based immune defense system is capable of identifying and destroying a single species of dangerous bacterial invaders that makes it into our digestive system when we accidentally ingest contaminated food or water. What is even more remarkable, it accomplishes this task by recognizing the small number of potentially lethal bacteria in an ocean of a trillion other benevolent microbes living in your gut, the gut microbiota. Accomplishing this challenging task ensures that we can live with our gut microbiota in perfect harmony.

The lining of your gut is studded with a huge number of endocrine cells, specialized cells that contain up to twenty different types of hormones that can be released into the bloodstream if called upon. If you could clump all these endocrine cells together into one mass, it would be greater than all your other endocrine organs—your gonads, thyroid gland, pituitary gland, and adrenal glands—combined.

The gut is also the largest storage facility for serotonin in our body. Ninety-five percent of the body’s serotonin is stored in these warehouses. Serotonin is a signaling molecule that plays a crucial role within the gut-brain axis: It is not only essential for normal intestinal functions, such as the coordinated contractions that move food through our digestive system, but it also plays a crucial role in such vital functions as sleep, appetite, pain sensitivity, mood, and overall well-being. Because of the widespread involvement in regulation of some of these brain systems, this signaling molecule is the main target of the major class of antidepressants, the serotonin reuptake inhibitors.

If our gut’s sole function was to manage digestion, why would it contain this unparalleled assembly of specialized cells and signaling systems? One answer to this question is a largely unknown feature of our gut, its crucial function as a vast sensory organ, covering the largest surface of our bodies. When spread out, the gut has the size of a basketball court, and it is packed with thousands of little sensors that encode the vast amount of information that is contained in your food in the form of signaling molecules, from sweet to bitter, from hot to cold, and from spicy to soothing.

The gut is connected to the brain through thick nerve cables that can transfer information in both directions and through communication channels that use the bloodstream: hormones and inflammatory signaling molecules produced by the gut signaling up to the brain, and hormones produced by the brain signaling down to the various cells in the gut, such as the smooth muscle, the nerves, and the immune cells, changing their functions. Many of the gut signals reaching the brain will not only generate gut sensations, such as the fullness after a nice meal, nausea and discomfort, and feelings of well-being, but will also trigger responses of the brain that it sends back to the gut, generating distinct gut reactions. And the brain doesn’t forget about ...