Gut: The Inside Story of Our Body's Most Underrated Organ (Revised Edition)
304
Gut: The Inside Story of Our Body's Most Underrated Organ (Revised Edition)
304Paperback(Revised Edition)
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Overview
AS SEEN ON NETFLIX’S HACK YOUR HEALTH: THE SECRETS OF YOUR GUT
“Everything you ever wanted to know about the gut (and then some).”
—SELF
Discover the secrets of your digestive system—and how to hone a healthy gut—plus new research on the mind-gut connection.
With quirky charm, science star and medical doctor Giulia Enders explains the gut’s magic, answering questions like: What’s really up with gluten and lactose intolerance? How does the gut affect obesity? What's the connection between our microbiome and mental health? Why does acid reflux happen? In this revised edition of her beloved bestseller, Enders includes a new section on the brain-gut connection, and dives into groundbreaking discoveries of psychobiotics—microbes with psychological effects that can influence mental health conditions like depression and even stress.
For too long, the gut has been the body’s most ignored and least appreciated organ. But it does more than just dirty work; it’s at the core of who we are, and this beguiling book will make you finally listen to those butterflies in your stomach: they’re trying to tell you something important.
Product Details
| ISBN-13: | 9781771643764 |
|---|---|
| Publisher: | Greystone Books |
| Publication date: | 03/27/2018 |
| Edition description: | Revised Edition |
| Pages: | 304 |
| Sales rank: | 17,309 |
| Product dimensions: | 5.50(w) x 8.40(h) x 0.90(d) |
| Lexile: | 1120L (what's this?) |
About the Author
Read an Excerpt
The world is a much more interesting place if we look beyond what is visible to the naked eye. There is so much more to see! If we start to look more closely, a tree can be more than a spoon-shaped thing. In a highly simplified way, “spoon” is the general shape we perceive when we look at a tree: a straight trunk and a round treetop. Seeing that shape, our eyes tell us “spoon-like thing.” But there are at least as many roots beneath the ground as there are branches above it. Our brain should really be telling us something like “dumbbell,” but it doesn’t. The brain gets most of its input from our eyes, and that information is very rarely in the form of an illustration in a book showing trees in their entirety. So, it faithfully construes a passing forest landscape as “spoon, spoon, spoon, spoon.”
As we “spoon” our way through life like this, we overlook all sorts of wonderful things. There is a constant buzz of activity beneath our skin. We are perpetually flowing, pumping, sucking, squeezing, bursting, repairing, and rebuilding. A whole crew of ingenious organs works so perfectly and efficiently together that, in an adult human being, they require no more energy than a 100-watt light bulb. Each second, our kidneys meticulously filter our blood—much more efficiently than a coffee filter—and in most cases they carry on doing so for our entire lives. Our lungs are so cleverly designed that we use energy only when we breathe in. Breathing out happens without any expenditure of energy at all. If we were transparent, we would be able to see the beauty of this mechanism: like a wind-up toy car, only bigger, softer, and more lung‑y. While some of us might be sitting around thinking “Nobody cares about me!”, our heart is currently working its seventeen-thousandth twenty-four hour shift—and would have every right to feel a little forgotten when its owner thinks such thoughts.
If we could see more than meets the eye, we could watch as a clump of cells grows into a human being in a woman’s belly. We would suddenly see how we develop, roughly speaking, from three tubes. The first tube runs right the way through us, with a knot in the middle. This is our cardiovascular system, and the central knot is what develops into our heart. The second tube develops more or less parallel to the first along our back. Then it forms a bubble that migrates to the top end of our body, where it stays put. This tube is our nervous system, with the spinal cord, including the brain, at the top and myriad nerves branching out into every part of our body. The third tube runs through us from end to end. This is our intestinal tube—the gut.
The intestinal tube provides many of the furnishings of our interior. It grows buds that bulge out farther and farther to the right and left. These buds will later develop into our lungs. A little bit lower down, the intestinal tube bulges again and our liver has begun to develop. It also forms our gall bladder and pancreas. But, most importantly, the tube itself begins to grow increasingly clever. It is involved in the complex construction of our mouth, creates our esophagus, with its ability to move like a break dancer, and develops a little stomach pouch so we can store food for a couple of hours. And, last but not least, the intestinal tube completes its masterpiece—the eponymous intestine or gut.
The masterpieces of the other two tubes—the heart and the brain—are generally held in high regard. We see the heart as central to life since it pumps blood around the body. The brain is admired for its ability to create a dazzling array of new mental images and concepts every second. But the gut, in most people’s eyes, is good for little more than going to the toilet. Apart from that, people think, it just hangs around inside our bellies, letting off a little “steam” every now and then. People do not generally credit it with any particular abilities. It would be fair to say that we underestimate our gut. To put it more bluntly, we don’t just underestimate it, we are ashamed of it—more “guilt feeling” than “gut feeling”!
I hope this book will change that by making use of the wonderful ability that books possess to show us more than the world we see around us. Trees are not spoons, and the gut is our body’s most underrated organ. This is its inside story.
How Does Pooping Work? And Why That’s an Important Question
My flatmate wandered into the kitchen one day, saying, “Giulia, you study medicine—so how does pooping work?” It probably wouldn’t be a great idea for me to begin my autobiography with that question, but that little query did literally change my life. I withdrew to my room, sat on the floor, and was soon poring over three different textbooks. The answer I eventually discovered left me flabbergasted. This unspectacular daily necessity turned out to be far more sophisticated and impressive than I ever would have imagined.
Every time we go to the toilet, it’s a masterly performance—two nervous systems working tirelessly in tandem to dispose of our waste as discreetly and hygienically as possible. Very few other animals do their business in such an admirable and orderly manner. Our bodies have developed all sorts of mechanisms and techniques to help us poop properly. The first surprise is the sophistication of our sphincters. The vast majority of people are familiar only with the outer sphincter: the muscle we can consciously control, opening and closing it at will. There is another, very similar muscle close by—but this is one we can’t control consciously.
Each of the two sphincters looks after the interests of a different nervous system. The outer muscle is a faithful servant of our consciousness. When our brain deems it an unsuitable time to go to the toilet, the external sphincter obeys and stays closed with all its might. The internal sphincter represents our unconscious inner world. Whether Great-Aunt Bertha approves of breaking wind or not is no concern of the sphincter ani internus. It is only interested in making sure everything is okay inside us. Is the gas pressure rising? The inner sphincter’s mission is to keep all unpleasantness at bay. If it had its way, Great-Aunt Bertha would break wind more often. The main thing for the internal sphincter is to keep everything comfortable and in its place.
These two sphincter muscles have to work as a team. When what’s left of our food reaches the internal sphincter, that muscle’s reflex response is to open. But it does not just open the floodgates and let everything out, leaving the outer sphincter to deal with the deluge. First, it allows a small “taster” through. The space between the internal and external sphincter muscles is home to a large number of sensor cells. They analyze the product delivered to them, test it to find out whether it is solid or gaseous, and send the resulting information up to the brain. This is the moment when the brain realizes, “It’s time to go to the toilet!” Or maybe, “It’s just a bit of wind.” It then does what it is so good at with its conscious awareness: it adapts to the environment we find ourselves in. It compares the information it receives from our eyes and ears to the data in its memory bank of past experience. In this way, the brain takes just a matter of seconds to make an initial assessment of the situation and send a message back to the sphincter: “I’ve had a look and we’re at Great-Aunt Bertha’s, in the living room. We might get away with breaking a little wind if we can squeeze it out
silently—anything more solid might not be such a good idea.”
The external sphincter gets the message and dutifully squeezes itself closed even more tightly than before. The internal sphincter receives this signal from its more outgoing partner and respects the decision—for now. The two muscles work together and maneuver the taster back into a holding pattern. Of course, it will have to come out sooner or later, just not here and not now. After a while, the internal sphincter will simply give it a try with another little taster. If by then we’re back within our familiar four walls, it’s full steam ahead!
Our internal sphincter is a no-nonsense little guy. His motto is “If it’s gotta come out, it’s gotta come out!” Not much room for argument there. The external sphincter, on the other hand, has to deal with the vagaries of the outside world and its many options. It might, theoretically, be possible to use this stranger’s toilet, but is that a good idea? Have my new girlfriend/boyfriend and I been together long enough for farting in front of each other to be okay—and if so, is it down to me to break the ice and go first? If I don’t go to the toilet now, can I wait until this evening or will I get caught short?
The considerations of our sphincter may not sound worthy of a Nobel Prize, but in fact they are concerned with some of the most basic questions of human existence: how important to us is our inner world, and what compromises should we make to get by in the external world? There are those who clench with all their might to keep the wind in, come what may, eventually struggling home wracked with bellyache. Others get Granny to pull on their finger at a family party, making a funny, if slightly inappropriate, magic show out of their need to break wind. The best compromise is probably somewhere in the middle.
If we suppress our need to go the toilet too often or for too long, our internal sphincter begins to feel browbeaten. In fact, we are able to reeducate it completely. That means the sphincter and the surrounding muscles have been disciplined so often by the external sphincter that they become cowed. If communication between the two sphincters breaks down completely, constipation can result.
Even without such defecatory discipline, something very similar can happen to women during labor. Childbirth can cause tearing of the delicate nerve fibers that allow the two muscles to communicate with each other. The good news is that those nerves can heal and reconnect. Irrespective of whether the damage was caused by childbirth or in some other way, one good treatment option is what doctors call biofeedback therapy. Biofeedback therapy is offered by some gastroenterologists or gastroenterology departments. It teaches the two sphincters to overcome their estrangement and get to know each other again. A machine is used to measure how efficiently the internal and external sphincters are working together. If messages from one to the other get through, the patient is rewarded with a sound or light signal. It’s like one of those quiz shows on early evening television, where the whole set lights up and fanfares blare when a contestant gets the answer right—only it’s at a medical practice, not on television, and the “contestant” has a sensor electrode up his or her butt. That may seem extreme, but it’s worth it. When the two sphincters are talking properly to each other again, going to the little girls’ or little boys’ room is an altogether more pleasant experience.
Sphincters, sensor cells, consciousness, and electrode-up-the-butt quiz shows. My flatmate was probably not expecting all that in answer to his casual question about pooping, nor did the group of rather prim female business studies students who had meanwhile gathered in the kitchen for his birthday party. Still, the evening turned out to be fun, and it made me realize that a lot of people are actually interested in the gut. Some interesting new questions were raised at the birthday party. Is it true that we don’t sit on the toilet properly? How can we burp more easily? Why can we get energy from steaks, apples, or fried potatoes, for example, but cars are much more restricted in their fuel options? Why do we have an appendix? Why are feces always the same color?
My flatmates have learned to recognize the familiar look on my face when I rush into the kitchen, bursting to tell them my latest gut anecdote—like the one about the tiny squat toilets and luminous poop.
Table of Contents
Preface 7
1 Gut Feeling 7
How Does Pooping Work? And Why That's an Important Question 12
The Gateway to the Gut 21
The Structure of the Gut 32
What We Really Eat 48
Allergies and Intolerances 58
A Few Facts About Feces 69
2 The Nervous System Of the Gut 77
How Our Organs Transport Food 81
Reflux 93
Vomiting 98
Constipation 108
The Brain and the Gut 122
3 The World of Microbes 143
I Am an Ecosystem 147
The Immune System and Our Bacteria 152
The Development of the Gut Flora 159
The Adult Gut Population 167
The Role of the Gut Flora 182
The Bad Guys-Harmful Bacteria and Parasites 196
Of Cleanliness and Good Bacteria 223
4 Update on the Brain-Gut Connection 261
New Discoveries 264
Clever Cravings for Fermented Foods 275
Acknowledgments 281
References 282
