16,99 €
Mehr erfahren.
- Herausgeber: John Wiley & Sons
- Kategorie: Fachliteratur
- Sprache: Englisch
Combat digestive symptoms and get trustworthy information to keep yourself healthy from the inside out
Gut Health For Dummies can help you restore and optimize your gut and its microbes, for better health day to day. Clear away the confusion and debunk the unscientific information found on social media with this essential guide. You’ll learn what makes the gut so important and how it influences the rest of your body, including your brain. Figure out how to manage digestive disorders and gut symptoms, confidently navigate the world of probiotics and other gut health supplements, and find inspiration for the diet and lifestyle changes that will support your health for years to come. This jargon-free Dummies guide will set you on the right path, giving you tips for adopting healthy habits, healing your gut biome, and being proactive for wellbeing and longevity.
- Learn how the gut works and explore what may be causing your digestive symptoms
- Combat IBS and other gut disorders with the latest science
- Steer clear of myths, scams, and misinformation—discover what actually works
- Be proactive in managing your gut health to ensure robust health and wellbeing at every age
For those who currently experience gastrointestinal symptoms, and anyone interested in learning about evidence-based ways to optimize gut health, Gut Health For Dummies is the right choice.
Sie lesen das E-Book in den Legimi-Apps auf:
Seitenzahl: 600
Veröffentlichungsjahr: 2024
Ähnliche
Gut Health For Dummies®
To view this book's Cheat Sheet, simply go to www.dummies.com and search for “Gut Health For Dummies Cheat Sheet” in the Search box.
Table of Contents
Cover
Title Page
Copyright
Introduction
About This Book
Foolish Assumptions
Icons Used in This Book
Beyond the Book
Where to Go from Here
Part 1: Understanding Why Gut Health Is Important
Chapter 1: No Healthy Gut, No Health Glory
Defining Gut Health
Picturing Your Gut
Managing Your Gut Health
Chapter 2: Grasping How the Digestive System Works
Keeping the Outside from Coming Inside
Reviewing the Parts of the Digestive Tract and How They Work
Recognizing the Essentials about Gut Function
Chapter 3: Getting to Know Your Gut’s Ecosystem of Microbes
Meeting Your Gut Microbiome
Finding Out What Your Gut Microbiome Does for You
Understanding How You Get Your Unique Gut Microbiome
Aiming For Diversity and Resilience of Your Gut Microbiome
Chapter 4: Discovering What Influences Gut Health
Eyeing How Medications Alter Your Gut
Linking Eating Habits to Gut Health
Connecting Exercise and Fitness to Gut Health
Seeing How Your Brain Influences Your Gut
Tying Sleep Habits to Gut Health
Exploring How Infections Alter Your Gut
Influencing Gut Health — Other Factors at Play
Chapter 5: Connecting the Dots from Gut Health to Overall Health
Seeing How the Gut Connects with Other Organ Systems
Researching the Gut and What May Cause Diseases
Linking the Gut to Specific Diseases and Conditions
Preventing Disease through the Gut
Part 2: Restoring Your Gut Health
Chapter 6: Demystifying Digestive Symptoms
Understanding Who Gets Digestive Symptoms
Clarifying Specific Digestive Symptoms
Identifying Charlatan Conditions
Chapter 7: Understanding Digestive Diagnoses
Diagnosing Digestive Disorders
Looking At the Major Digestive Disorders
Embracing Your Diagnosis
Identifying the Types of Interventions for Digestive Disorders
Chapter 8: Empowering Yourself without a Diagnosis
Progressing toward Health
Staying Hopeful
Chapter 9: Navigating Life with Digestive Symptoms
Managing Your Digestive Symptoms
Taking Advantage of Technology
Getting Support
Part 3: Optimizing Your Gut Health
Chapter 10: Eating for Good Gut Health
Covering the Nutrition Basics
You Are What Your Gut Microbes Eat
Discovering the Principles of Gut-Friendly Diets
Navigating the Biotics
Getting Personal with Diet
Arming Yourself with Practical Tips for a Gut-Friendly Diet
Chapter 11: Adjusting Your Lifestyle For Long-Term Gut Health
Improving Your Sleep Habits
Exercising on a Regular Basis
Managing Stress
Going Outside
Looking at Other Lifestyle Factors
Chapter 12: Becoming Savvy with Gut Health Science
Seeking Science-Based Information on Gut Health
Making Sure You Don’t Waste Your Money on Bogus Products and Tests
Part 4: Nourishing Yourself and Your Gut
Chapter 13: Nourishing Soups & Salads
Making Gut-Healthy Soups
Assembling Salads for a Well-Fed Gut
Chapter 14: Gut-Friendly Main Courses
Satisfying Your Gut with Plant-Based Meals
Enjoying Meat and Fish in a Gut-Happy Dish
Chapter 15: Sustaining Sides & Snacks
Supporting Gut Microbes with Sides
Making Some Gut-Lovin’ Snacks
Chapter 16: Digestive-Friendly Desserts
Baking Muffins and Cakes to Feed Your Gut Microbes
Creating Cookies and Other Treats for Delightful Digestion
Part 5: Supporting Health through the Gut at Times in Life
Chapter 17: Paying Attention to Gut Health in Pregnancy, Birth, and Infancy
Supporting Gut Health during Pregnancy
Comprehending How Events at Birth Influence the Gut
Developing a Healthy Gut in the First Three Months of Life
Chapter 18: Fostering Good Gut Health in Children and Teens
Cultivating Good Gut Health through the First Year of Life
Nurturing Gut Health in Childhood
Encouraging Good Gut Health in Teens
Chapter 19: Maintaining Gut Health in Older Age
Finding Out How to Maintain a Healthy Gut in Older Age
Discovering the Secrets of Gut Health and Longevity
Part 6: The Part of Tens
Chapter 20: Ten Foods for Better Gut Health
Onions
Garlic
Leeks
Jerusalem Artichokes
Dandelion Greens
Yogurt
Kefir
Kimchi
Sauerkraut
Fermented Pickles
Chapter 21: Ten Myths about Gut Health Debunked
All Beneficial Microorganisms Are Probiotics
Fermented Foods Are Good Sources of Probiotics
Probiotics Add Healthy Bacteria to Your Gut Microbiome
Different Probiotics Are Interchangeable
Multiple Strains Are More Effective Than Single Strains
You Shouldn’t Take Probiotics While Taking Antibiotics
Probiotics Aren’t Regulated
Prebiotics and Fiber Are the Same
Postbiotics Are Metabolites Produced by Bacteria in Your Gut
Gut Microbiome Tests Can Give You Information to Shape Your Diet
Index
About the Author
Connect with Dummies
End User License Agreement
List of Illustrations
Chapter 2
FIGURE 2-1: The parts of the gut barrier.
FIGURE 2-2: The parts of the digestive tract.
FIGURE 2-3: The Bristol Stool Scale, showing different categories of stool form...
Chapter 3
FIGURE 3-1: Example of how a bacterium is classified at different levels.
Chapter 5
FIGURE 5-1: The global burden of infectious diseases has decreased while the bu...
Chapter 8
FIGURE 8-1: A written record of your gut symptoms and interventions.
Chapter 15
FIGURE 15-1: A jicama.
Guide
Cover
Table of Contents
Title Page
Copyright
Begin Reading
Index
About the Author
Pages
i
ii
1
2
3
4
5
7
8
9
10
11
12
13
14
15
16
17
19
20
21
22
23
24
25
26
27
28
29
30
31
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
303
304
305
306
307
308
309
310
311
312
313
314
315
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
Gut Health For Dummies®
Published by: John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030-5774, www.wiley.com
Copyright © 2024 by John Wiley & Sons, Inc., Hoboken, New Jersey
Published simultaneously in Canada
No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning or otherwise, except as permitted under Sections 107 or 108 of the 1976 United States Copyright Act, without the prior written permission of the Publisher. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, (201) 748-6011, fax (201) 748-6008, or online at www.wiley.com/go/permissions.
Trademarks: Wiley, For Dummies, the Dummies Man logo, Dummies.com, Making Everything Easier, and related trade dress are trademarks or registered trademarks of John Wiley & Sons, Inc., and may not be used without written permission. All other trademarks are the property of their respective owners. John Wiley & Sons, Inc., is not associated with any product or vendor mentioned in this book.
LIMIT OF LIABILITY/DISCLAIMER OF WARRANTY: WHILE THE PUBLISHER AND AUTHORS HAVE USED THEIR BEST EFFORTS IN PREPARING THIS WORK, THEY MAKE NO REPRESENTATIONS OR WARRANTIES WITH RESPECT TO THE ACCURACY OR COMPLETENESS OF THE CONTENTS OF THIS WORK AND SPECIFICALLY DISCLAIM ALL WARRANTIES, INCLUDING WITHOUT LIMITATION ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. NO WARRANTY MAY BE CREATED OR EXTENDED BY SALES REPRESENTATIVES, WRITTEN SALES MATERIALS OR PROMOTIONAL STATEMENTS FOR THIS WORK. THE FACT THAT AN ORGANIZATION, WEBSITE, OR PRODUCT IS REFERRED TO IN THIS WORK AS A CITATION AND/OR POTENTIAL SOURCE OF FURTHER INFORMATION DOES NOT MEAN THAT THE PUBLISHER AND AUTHORS ENDORSE THE INFORMATION OR SERVICES THE ORGANIZATION, WEBSITE, OR PRODUCT MAY PROVIDE OR RECOMMENDATIONS IT MAY MAKE. THIS WORK IS SOLD WITH THE UNDERSTANDING THAT THE PUBLISHER IS NOT ENGAGED IN RENDERING PROFESSIONAL SERVICES. THE ADVICE AND STRATEGIES CONTAINED HEREIN MAY NOT BE SUITABLE FOR YOUR SITUATION. YOU SHOULD CONSULT WITH A SPECIALIST WHERE APPROPRIATE. FURTHER, READERS SHOULD BE AWARE THAT WEBSITES LISTED IN THIS WORK MAY HAVE CHANGED OR DISAPPEARED BETWEEN WHEN THIS WORK WAS WRITTEN AND WHEN IT IS READ. NEITHER THE PUBLISHER NOR AUTHORS SHALL BE LIABLE FOR ANY LOSS OF PROFIT OR ANY OTHER COMMERCIAL DAMAGES, INCLUDING BUT NOT LIMITED TO SPECIAL, INCIDENTAL, CONSEQUENTIAL, OR OTHER DAMAGES.
For general information on our other products and services, please contact our Customer Care Department within the U.S. at 877-762-2974, outside the U.S. at 317-572-3993, or fax 317-572-4002. For technical support, please visit https://hub.wiley.com/community/support/dummies.
Wiley publishes in a variety of print and electronic formats and by print-on-demand. Some material included with standard print versions of this book may not be included in e-books or in print-on-demand. For more information about Wiley products, visit www.wiley.com.
Library of Congress Control Number: 2024931600
ISBN: 978-1-394-22658-0 (pbk); ISBN 978-1-394-22660-3 (ebk); ISBN 978-1-394-22659-7 (ebk)
Introduction
I can’t convey how exciting it’s been to watch gut health gradually emerge into the mainstream. Over a decade ago when I was experiencing debilitating gut symptoms every day, digestion was kept very hush-hush. The science was just starting to emerge, and useful science-based resources were almost nonexistent. When I started writing about gut health and the microbiome, most people who knew me were perplexed. More than once I took an editor’s call in a coffee shop and the people at the next table — overhearing me talk about digestion — discreetly moved to another location.
But somewhere along the line, gut health went big. Maybe it was the incredible advancements in gut microbiome science or the publication of popular books on the digestive system, such as Giulia Enders’ Gut. Maybe it was the fact that fecal matter became established as a lifesaving cure for recurrent Clostridioides difficile infection. Now gut health is everywhere — in popular books, on social media, in blogs, in newspapers and online articles, and in documentary films — and now in this book, Gut Health For Dummies.
Whether you’re here out of desperation to rid yourself of symptoms or you’re a fan of GutTok or other gut health content on social media, you’ve come to the right place. This book gives a solid scientific grounding in everything related to the gut — and this exciting journey shines a light on some dark and twisty corners of your body, with lots of surprising facts along the way. If you become squeamish at any time during this journey, just put down the book, pour yourself a tall glass of water, and remind yourself that what goes in must come out in one way or another. Appreciate that the gut is an incredible, complex system that enables you to be who you are as a human.
Gut health is getting more exposure at just the right time — because more and more people are experiencing digestive health problems that affect their lives. According to the American Gastroenterological Association, up to 70 million people in the United States have a gastrointestinal disease that interferes with their quality of life. And digestive problems have gotten in the way of desired activities for 40 percent of people at some point. In Canada, the incidence of digestive disease is even higher than in the United States — more than 50 percent of people are affected by symptoms. Despite these high numbers, many people delay seeking medical advice for gut-related issues. I hope this book brings clarity about your gut health experiences so you feel confident seeking the care you need — and take proactive steps to avoid gut health problems for many years into the future.
About This Book
Gut Health For Dummies isn’t like the other gut health books on bookshelves. Most books about gut health purport to have the one-and-only solution to fix your gut health, whether it’s a six-step plan, a restrictive diet, or an expensive array of supplements. The problem with those approaches is that they don’t have adequate scientific support: They may have worked well for some person at a particular time, but they’re not shown to work reliably. And they’re often short-sighted, treating diet as the only thing that matters for gut health. (Spoiler alert: This book identifies many different aspects of your lifestyle that converge to shape your gut health.)
I suffered through years of digestive symptoms without a diagnosis and eventually found relief by changing multiple aspects of my lifestyle, which I share throughout this book. Now, I’m passionate about understanding the science and knowing how to apply it in real life, so everything I report in these pages is based on genuine scientific findings and expert opinion, without hyping any individual findings. Because I make a living working with scientists in this field, I take great care to ensure that everything I say is appropriate and evidence-based according to what they’d expect.
Here I give you the knowledge to tell what claims and information are scientifically backed — so you can understand which products are likely to work versus which ones are relying on more of a wish and a prayer. When you’re able to evaluate products with a critical eye, you’re not at the mercy of whichever company has the biggest marketing budget. I aim to create the resource that I never had when I suffered from my own gut health issues and felt bombarded by all kinds of confusing and expensive products, all claiming to cure what ailed me. Now with the increased popularity of gut health, the market is even more saturated with products purporting to fix your gut. However, I understand that daily decisions are complex, so if you end up deciding, because of a friend’s recommendation or a social media influencer, that you want to try consuming a product with no scientific proof that it works, that’s your choice. I only hope you’ll be able to navigate your way through the world of gut health with awareness and better confidence.
In true Dummies style, the information in this book is presented in a clear, concise format with practical tips throughout. I capture the latest scientific thinking and translate it into everyday actions that represent the best-known ways to take care of your gut throughout your life.
This book extensively covers the microbiome of your gut. Your digestive tract microbiome is really several different microbiomes in different locations. Yet the microbiome of the colon is by far the most frequently studied because of the ease of collecting samples. (I mean, everyone deposits samples of this microbiome regularly into the toilet.) So, the term “gut microbiome” in scientific papers most often refers to the colonic, or fecal, microbiome. Throughout this book, therefore, gut microbiome refers to the colonic microbiome unless otherwise specified.
Sources of information about gut health often use dysbiosis to refer to a disrupted or abnormal gut microbiome. Dysbiosis can look a million different ways, even for a single disease. It can’t even be defined as an imbalance between good and bad bacteria in the microbial ecosystem because the concepts of “good” and “bad” simply don’t apply to microorganisms. For these reasons, dysbiosis has fallen out of favor in the scientific community, and I avoid it as well in this book. I tend to use the general terms “difference” or “disturbance” when talking about gut microbiome alterations associated with poorer health, lest people think dysbiosis is something that can be specifically defined and diagnosed.
The recipes in this book are complete, but they may not spell out every detail of prepping and cooking the food. For example, certain steps and techniques in cooking are standard no matter what you’re preparing. In addition, I require specific types of ingredients and also want to make sure that you adhere to a few of my other cooking preferences. Take a quick look at the following list for points that apply to all the recipes:
Fruits and vegetables are washed under cold running water before using.
Pepper is freshly ground pepper. Invest in a pepper mill and give it a few cranks when you want pepper bursting with flavor.
Fresh herbs are specified in many of the recipes for their bright, authentic flavor. But you can still make a recipe if you don’t plan to use these by substituting dry herbs, using one-third the amount of fresh.
Dairy products are low-fat.
Eggs are large unless otherwise indicated.
Olive oil is extra-virgin unless otherwise indicated.
All onions are sweet unless otherwise indicated.
Water is filtered water.
All temperatures are Fahrenheit.
Keep pots uncovered unless I tell you to put on the lid.
This tomato icon indicates that the recipe is vegetarian.
Foolish Assumptions
When writing this book, I make the following assumptions about you:
You’ve heard about gut health but may not be familiar with the scientific jargon, so I define new terms as they’re introduced.
You’re suffering from digestive symptoms and you’re open to seeking medical help and taking advantage of the interventions that have the best scientific support.
Even if you don’t have regular digestive symptoms, you’re also interested in leveraging the best science to maintain your gut health and overall wellness.
Icons Used in This Book
Throughout this book you’ll see the following icons to draw your attention to certain paragraphs.
When you see this icon, it flags practical advice for putting gut health science into practice.
This icon highlights key points that help you gain a better understanding of gut health in general.
This icon indicates more detailed (nonessential) information for people who want to level up their knowledge.
This icon alerts you about what to watch out for if you want to avoid gut health problems.
This icon shows where a leading scientist weighs in specially for this book to bring you the latest knowledge in the field.
Beyond the Book
I hope you continue your gut health journey even after you read the last page of this book. For more information, you can check out the book’s accompanying Cheat Sheet — go to www.dummies.com and search for “Gut Health For Dummies Cheat Sheet.”
This book is also available as an audiobook — check it out on your favorite audiobook platform.
If you want to share any feedback with me, contact me through my website: www.bykriscampbell.com.
Where to Go from Here
This book is designed so you can jump in and start reading anywhere you want. If you prefer a refresher on the digestive tract and how it works, Chapter 2 is the ideal place to start. But if you have a clear memory of those eighth-grade lessons on the digestive tract and need to get up to speed on the microbes living there, start at Chapter 3.
For symptom SOS, jump right in at Chapter 6, or if you’re lucky enough not to suffer from major digestive symptoms, you can skip to Chapter 10, which covers how to optimize your diet for gut health. Chapters 13 to 16 have some recipes to try out for supporting your gut if you’re a generally healthy person.
If you’re not sure where to begin, flip through the table of contents or index and find a topic that piques your interest.
Part 1
Understanding Why Gut Health Is Important
IN THIS PART …
Explore the emerging meaning of gut health and how it’s different from digestive health.
Delve into the workings of the digestive system and how it achieves a fine balance between letting in what nourishes you and keeping out harmful substances.
Get a handle on the microorganisms that make their home in the digestive tract and examine what their surprisingly important roles are in maintaining your health.
Find out about the factors in your lifestyle that influence the gut microorganisms and gut health overall.
Discover the connections that scientists are making between your gut health and various diseases — not only digestive diseases, but also metabolic conditions, brain conditions, and more.
Chapter 1
No Healthy Gut, No Health Glory
IN THIS CHAPTER
Exploring what gut health means and why it’s so important
Visualizing your digestive system and how the parts work together
Recognizing approaches to managing your gut health
If your body is a temple, your gut is its grand, elaborate foyer. The gut serves as a point of entry for food, medicines, and other substances — and that’s where the action begins, but not everything makes it past this entrance hall. Some substances get sent out another door promptly, and others discard layers or become transformed before gaining access to other parts of the body through the gut barrier. The digestive system is your body’s primary interface with the outside environment, so it’s an area that’s not outside you, and not fully inside you either.
Just as managing visitors through the foyer helps keep order in the rest of the building, keeping your gut in good working order is essential for your body’s overall health. This chapter dives into what gut health is, then gives an overview of what the digestive tract looks like and how it functions. Finally, this chapter covers the essentials of managing your gut health if you have symptoms or if you want to optimize an already healthy gut.
Defining Gut Health
Decades ago, the term “gut health” didn’t even exist. And 10 years ago when I was starting to write about this field, people I interviewed told me the first thing that came to mind when they heard the word “gut” was a protruding belly (as in the phrase “beer gut”). But starting around 2014 I began to hear about gut health more and more, and now, gut health is a term people use all the time — in blogs, in the media, in ads, and elsewhere.
Gut health, however, is often used without necessarily having a clear definition. This section clarifies what gut health is so you can use this definition as you navigate this book.
Discovering the meaning of gut health
So far, scientists haven’t agreed on a definition of gut health. Some proposals for the meaning of this term are as follows:
Absence of a diagnosed digestive disease
Lack of any digestive symptoms
Optimal gut structure and function (including the configuration of the gut microbes)
None of these proposals, however, seem to capture the connotations of gut health today and why it’s such a popular topic. Clearly many people (myself included, at one time) who are free of diagnosed digestive disease still don’t have a healthy gut. And as for using digestive symptoms as the gold standard: Some signs of an unhealthy gut, such as gut barrier permeability or mild inflammation, may not result in symptoms but are nonetheless undesired and linked with health problems later on. Even optimal gut structure and function isn’t a definition of gut health that adequately accounts for why the concept is suddenly resonating with millions around the world.
Because of the general public’s growing awareness of the latest science on the gut microbiome and how digestive health relates to other body systems, gut health has come to mean something more like a state of well-being, both mental and physical, that’s enabled by what happens in the gut. Whereas the term “digestive health” narrowly refers to the digestive tract and how it functions, gut health extends to general wellness from the inside out. Because the gut is the body’s crossroads of digestion, immunity, and metabolic health, overall health and wellbeing can’t be achieved without a healthy gut. In other words, without gut health there’s no (overall) health glory.
Dietary intake is an important concept intertwined with gut health. The popular conceptualization of gut health appears to signal a new awareness about how people’s diets lead to measurable and direct consequences for physical and mental health. Diet, exercise, and other lifestyle factors were previously seen as having vague and long-term health benefits. But now scientists have found that these factors have almost immediate effects on your gut microbes, which are part of the mechanisms for broader health effects throughout the body. Clearly eating a single donut isn’t going to shorten a person’s lifespan, but donuts (with their high fat and sugar content) pressure the gut microbes in a certain way so that a habit of eating donuts maintains undesirable changes in the gut, which may take years to become visible through the rest of the body and have negative health consequences.
The current meaning of gut health, then, encompasses the optimal structure and function of the gut — with the acknowledgement that it may have the capacity to promote wellness or prevent illness, especially through what you eat.
Identifying components of gut health
Unfortunately, no hard and fast measures exist to confirm you have a healthy gut — and in fact the medical community is much more skilled at defining an unhealthy gut than a healthy gut. However, a healthy gut is generally associated with some specific outcomes:
Having fewer sick days
Not requiring a restrictive diet
Not needing medications for digestive health or other conditions
As for assessing gut health more precisely, five parameters may be relevant:
Digestive function:
Whether nutrients are broken down and absorbed properly
Digestive tract structure:
Whether the parts of the digestive tract are structurally intact, with no observable damage from inflammation or other injury
Motility:
If materials are moving through the digestive tract appropriately and at the right speed
Gut microbiota characteristics:
Whether the gut microbial composition and function is appropriate (even though a normal gut microbiota hasn’t yet been defined)
Gut-brain axis function:
Whether the communication channels between the gut and the brain support both gut and brain health
Scientists may one day come up with a precise list of how to measure each of these parameters to set a standard for a healthy gut, but until then, gut health is more of a judgment call. It includes conscious efforts to maintain health by using knowledge about what affects the digestive tract and its resident microorganisms, as discussed in Chapter 4 as well as Part 5.
Why gut health matters more than ever
Chronic (also called noncommunicable) diseases such as heart disease, cancer, respiratory disease, and diabetes, have become a global health emergency. The World Health Organization (WHO) says chronic diseases are responsible for 74 percent of deaths each year. A recent analysis estimated that, in U.S. adults older than 50, the number with a chronic disease will nearly double between 2020 and 2050 — and healthcare systems are poorly prepared to handle the increasing burden of these diseases.
But an opportunity exists to prove these predictions wrong and reverse the chronic disease trend. Importantly, the following preventable factors contribute to the risk of dying from a chronic disease:
Smoking
Physical inactivity
Harmful use of alcohol
Unbalanced diets
Air pollution
At least three of these factors — inactivity, alcohol, and dietary intake — are now known to have direct connections to health through the gut. Not to mention, scientists are uncovering connections between gut health and chronic diseases themselves as I explain in Chapter 5. Gut health can provide powerful day-to-day motivation to improve habits that have a direct effect on how likely you are to die from a chronic disease — and can perhaps even prevent chronic disease from occurring in the first place. Thus, gut health is at the center of a prevention revolution, empowering people to take charge of their health through diet and other aspects of their lifestyle.
From this perspective, gut health is one the keys to unlocking better health and longer, healthier lives. The current popularity of gut health is a positive sign that chronic diseases in your families and communities don’t have to match up with the latest bleak projections.
Picturing Your Gut
The digestive system includes all the organs and processes in your body that transform your food into energy and eliminate solid waste. A prerequisite for understanding gut health is knowing what the parts of your digestive system look like and how they function; these sections give you a preview.
Understanding how your gut works
The digestive tract is made up of the parts your food moves through — the mouth, esophagus, stomach, small intestine, large intestine, and anus — along with the accessory organs (liver, pancreas, and gallbladder) that produce the substances required to successfully digest your food.
The digestive system’s jobs are to break down food using different mechanical, chemical, and microbial processes, to absorb nutrients, and to send off the waste for elimination. Chapter 2 gives details on how these complex processes work.
Meeting the microbes
The 38 trillion microorganisms you harbor are critical to your body’s healthy functioning — and most of them reside in your digestive tract. Chapter 3 introduces you to these microorganisms: bacteria, archaea, fungi, and viruses. Scientists have techniques for not only identifying the composition of these microorganisms in your gut, but also figuring out their functions, or what their genes allow them to do.
Working from home in the gut, the microorganisms have incredibly important jobs that affect distant parts of the body. They strengthen your gut barrier, keep your immune system in check, make vitamins, transform and break down food and medicines, help control metabolism, and even guide your development from a young age.
One of the most exciting areas of science in the past 20 years (in my admittedly biased opinion) has been the study of gut microbes and their effects on overall health. So far the best-known way to get your microbial community to support your health is to keep it diverse and resilient in the face of perturbations.
Several main things are shown to influence your gut microbes and overall gut health as Chapter 4 details:
Medications you take
What you eat
Other aspects of your lifestyle
Your gut microbiome is particularly sensitive to your everyday choices and habits, which may impact your gut health and perhaps trigger digestive symptoms.
Linking gut health to how you feel
A lot happens in the dark depths of your gut, so you may wonder how much it affects how you feel, physically and mentally. Chapter 5 goes over the known connections between the gut and other organ systems in the body: the skin, respiratory system, liver, kidney, and central nervous system. By studying these communication channels, scientists are linking many specific diseases to gut health — and especially to alterations in the complex ecosystem of intestinal microbes.
In the industrialized world, many aspects of lifestyle have the inadvertent effect of destroying gut microbes, leading some scientists to wonder if missing microbes in people’s guts are responsible for the current epidemic of chronic diseases. On the bright side, evidence increasingly suggests that nurturing your gut health and keeping the microbial community diverse may have a positive impact on health, empowering you to prevent chronic disease to the extent it’s possible, rather than passively waiting for it to happen.
Managing Your Gut Health
Regardless of the state of your gut health at present, strategies exist for actively managing it. If you experience regular gut symptoms, the first step is accurately describing them to a medical professional who can determine whether or not they fit the pattern of a digestive disease. Then you can take further steps, either through medical management or lifestyle changes, that can help you gain more control over your overall health and wellness as I discuss in these sections.
Identifying symptoms
Everyone experiences unwanted gut health symptoms at some time. Chapter 6 gets to the bottom of your gut symptoms and helps you know how to describe them accurately, including which symptoms are your cue to seek medical advice.
Recognizing possible diagnoses
Some gut-related symptoms signal the presence of digestive disease. Chapter 7 goes through what to expect if you’re exploring a digestive disease diagnosis, including what crucial information to tell your doctor and some of the medical tests that may be necessary. That chapter also goes over some of the most common digestive diseases that doctors diagnose and the first steps to take post-diagnosis to make sure you have the most reliable information for your decision-making. I also outline the main categories of treatments for digestive diseases, the details of which should be guided by your healthcare practitioner.
Making dietary and other lifestyle changes
If you have gut symptoms without a digestive disease diagnosis, you can still follow a path of scientific evidence to lead you to appropriate interventions (actions you take with the intention to modify your health) that may bring you relief. Chapter 8 focuses on what to do if you don’t have an official digestive diagnosis and helps you know how to progress toward better health while navigating the safety and effectiveness of different gut health products and services.
Chapter 9 delves right into the practicalities of managing gut health symptoms in different places, including at home, in public, when visiting others, at work, and while travelling. The chapter is packed with pro tips on lessening the impact of symptoms on your life, including how to leverage apps and other technology, and how to seek social supports.
Diet is the controllable factor with the biggest impact on your gut health. Chapter 10 starts with the basics of nutrition and the dietary patterns that lead to better health through the actions of the gut microbes, and then covers the surprisingly simple science-backed principles for a diet that supports your gut health:
Every week, consume 30 or more varied plant sources of fiber.
Consume fermented foods every day.
Consume high quantities of live microorganisms — one billion or more — every day.
Consume low amounts of omega-6 fats and higher amounts of olive oil and other monounsaturated fats.
Avoid emulsifiers and noncaloric sweeteners in your diet.
For delicious inspiration on how to achieve gut-friendly dietary habits, Chapters 13–16 feature a wide array of recipes that support your gut microbes and gut health. Chapter 20 features ten gut-friendly foods to include in your diet each week.
Look to Chapter 10 to give you the lowdown on the biotics — that is, probiotics, prebiotics, synbiotics, and postbiotics — as well as on fermented foods. There I explain how to interpret these products’ marketing messages and sort out fact from fiction.
Diet isn’t the only way to adjust your lifestyle for better gut health with the aim of optimizing overall health. Additional powerful factors (see Chapter 11) include the following:
Sleep habits
Exercise
Stress management
Outdoor time
Small steps forward in these areas can have compounding effects on your overall health over time.
Staying proactive about gut health throughout life
Certain times of life are especially important for protecting gut health:
Pregnancy:
During this time, even though the fetus is sealed off from direct contact with gut microbes, the microbes of the mother-to-be may have indirect influences. Her microbes may be influenced by a range of factors, including:
Dietary choices
Probiotics
Stress
Antibiotics
Infections during pregnancy
Birth and the first three months of life:
Birth is the first exposure of the baby to the vast microbial world, with vaginal birth setting up the infant with a different collection of microbes than Caesarean section birth. Antibiotics and gestational age at birth strongly influence the baby’s first microbial collection, too. Subsequently in the first three months of life, diet (whether breastmilk or formula) has the biggest impact on the gut health of the infant. Various biotics may be added to formula to approximate important components of breastmilk.
The first year of life:
Throughout the first year of a child’s life, the factors that specially influence gut health are the transition to solid foods, antibiotics, and exposure to diverse (outdoor) microbes. The farm effect, whereby children who grow up on farms are protected from some chronic diseases later in life, is especially apparent during year one.
Childhood:
From the ages of 1 to 12 years, gut health is primarily supported by the following:
Good dietary habits
Outdoor microbe exposure
Reduction of stress or adverse childhood experiences
Adolescence:
By the time a person reaches adolescence, the gut is less dynamic and potentially less sensitive to external factors. However, a balanced diet and outdoor microbe exposure during adolescence can go a long way to supporting overall health from the gut outward.
Older age:
A gut health transition happens in older age — partly because of the normal process of aging and partly because of age-related diseases as well as lifestyle changes. Diet and biotics, as well as medication management, are the primary ways to support gut health to extend health span in older age.
Science progresses over time, so you’ll inevitably encounter new options for improving your gut health in the years to come — not to mention new sources of information that you’ll need to evaluate. Chapter 12 empowers you to think critically about gut health products and find out which ones have been scientifically tested and shown to work. You’ll be extra savvy about the science if you check out the top ten myths about gut health in Chapter 21.
Chapter 2
Grasping How the Digestive System Works
IN THIS CHAPTER
Taking a tour of your digestive tract and exploring how it works
Examining the way that food moves through your gut
Breaking down how your gut digests and absorbs nutrients
Understanding how your immune system interacts with digestion
What works hard while you’re working and works even harder when you take a coffee break? The answer: Your digestive system.
Constantly laboring to transform your food into energy and clear away the substances you no longer need, your digestive system is made up of your digestive tract plus the accessory organs (liver, pancreas, and gallbladder), which produce all the substances needed for digestion. The digestive tract (also known as the gastrointestinal tract, or gut) is essentially a long and winding tube going from your mouth all the way down to your bottom (anus). Every new influx of food — or coffee, for that matter — gives your digestive system something to contend with. But even when you don’t ingest food or liquid, this body system keeps working at a steady pace to replenish intestinal tissues and clear out residues.
The main functions of the digestive system are
Breaking down food through mechanical, chemical, and microbial processes
Absorbing nutrients
Eliminating waste products
This chapter gives you the grand tour of your digestive tract, orienting you to all the different parts and how they work — and presenting you with some surprising facts along the way.
Keeping the Outside from Coming Inside
The human digestive tract is a special zone that, strictly speaking, isn’t inside your body. Even when your lunch has disappeared from your plate and appears to be inside of you, it’s still on the outside — that is, the food is sequestered inside the central shaft of the digestive tract and kept there by the gut barrier. Only when some of the food components are broken down and allowed past the gut barrier are they considered truly inside your body because they then reach blood circulation and travel to where they’re needed. Everything that remains trapped in the digestive tract is swept through to the bottom end and eliminated completely through defecation.
How does the digestive tract keep substances outside from coming inside? It has a sophisticated gut barrier that includes two main parts as follows:
Epithelial cells:
Facing the intestinal
lumen
(the space inside the digestive tract) is a layer of intestinal epithelial cells that’s only one cell thick. These cells that line the inside of the intestines are connected by tight junctions — protein structures that open and close like Venetian blinds to let in nutrients while keeping out harmful substances.
The mucus layer:
On top of the epithelial cells is a layer of mucus, gel-like proteins that form a squishy surface. The mucus layer in the gut protects the sensitive epithelial cells and provides stability in the chemical environment, separating the epithelial cells from digestive juices, bacteria, or toxins within the lumen.
Chapter 3
discusses the microbes that sit atop the mucus layer.
THE LOWDOWN ON LEAKY GUT
In previous decades, a trendy condition called leaky gut was blamed for a huge range of ailments, from skin irritation to brain fog. The way leaky gut was used in alternative health, it served as a diagnosis even though scientists had little evidence for its existence. However, more recently the concept of intestinal permeability is being observed in scientific investigations and is also coming to be known as leaky gut — a state in which more space exists between the tight junctions of the gut, allowing some harmful substances to cross the gut barrier. Today, despite increased acknowledgment of this phenomenon in scientific circles, leaky gut is better characterized as a mechanism of how symptoms occur, rather than a diagnosis. Find more details in Chapter 6.
Immune cells underneath these layers also provide fortification against any harmful substances that could potentially reach the rest of the body. Figure 2-1 illustrates the gut barrier.
© John Wiley & Sons, Inc.
FIGURE 2-1: The parts of the gut barrier.
Reviewing the Parts of the Digestive Tract and How They Work
As a living organism you need energy, and your digestive system creates that energy from things out in the world that contain what you need. For example, a plum or a piece of rye bread has plenty of components for you to digest and nourish your body. But if you happened to eat a piece of paper or some candle wax, they’d move through your digestive system without giving you nourishment.
Figure 2-2 shows the digestive tract. Food moves from top to bottom, through the following parts:
Oral cavity (mouth) and oropharynx
Esophagus
Stomach
Small intestine
Large intestine
Anus
Each part of the digestive tract either moves food and liquid, or it helps break it into smaller parts — some of which can be absorbed and shipped around the body to where they’re needed. Enzymes (substances assisting chemical reactions) are essential to the food breakdown. Nerves as well as various hormones help control the digestive processes. (Refer to the section “Recognizing the Essentials about Gut Function” later in this chapter for more information.)
Each part of the digestive tract also harbors live microorganisms that participate in digestion and other critical body functions. Chapter 3 covers these microbial contributors in greater detail.
Many components of your food are absorbed as they make their way through the digestive tract. But some go through, from end to end. Take, for example, the outer covering of a kernel of corn, called the pericarp. You may see evidence of this fibrous food component in your stool after it completes the entire digestive tract journey. The following paragraphs trace the basic journey of a corn kernel on its winding path from the mouth to the stomach and all the way to the toilet.
© John Wiley & Sons, Inc.
FIGURE 2-2: The parts of the digestive tract.
THE MAN WHO ATE BICYCLES
You probably have a good idea of what’s food and what’s not — a pear is perfectly fine to eat, but a pair of boots isn’t. Yet there once was a man who ate all manner of unusual items. Michel Lotito, born in 1950 in France, developed a method for eating non-nutritious meals consisting of bicycles, television sets, and shopping carts. He’d disassemble them, cut them into small pieces, and consume the pieces systematically with mineral oil and lots of water.
Doctors determined that he had an unusually thick stomach lining and extra powerful stomach juices that allowed him to consume these objects. From the age of 16, Lotito consumed objects on stage as an entertainer, acquiring the nickname Monsieur Mangetout (Mr. Eat-All). The list of items he consumed throughout his life included 18 bicycles, six chandeliers, two beds, and a Guinness Book of Records plaque that he was awarded for the strangest diet.
The mouth and oropharynx
The mouth (also called the oral cavity) kicks off the digestion process as soon as you ingest a piece of food. Chewing is typically the first digestive activity that occurs in the mouth — a mechanical process of physically breaking down the food into smaller pieces. As saliva mixes with the food, some of its components also start the chemical digestion of certain carbohydrates and fats — for example, some enzymes called lingual lipases start to break down triglycerides (a type of fat that circulates in your blood and is used for energy).
As for the hypothetical corn kernel you’ve ingested, the mouth is where it’s chewed and pushed around by the tongue, with the fibrous pericarp remaining intact. When swallowed, it passes through the oropharynx (the back part of the mouth, leading to the esophagus). And in a feat of muscular gymnastics, a flap called the epiglottis closes off the airway at the exact right moment to prevent you from choking on the corn kernel as you swallow.
The esophagus
The next part of the digestive tract is the esophagus, the tube connecting the back of the throat to the stomach.
Muscular contractions called peristalsis push the corn kernel down through the esophagus. Peristalsis, a major process that keeps the food moving, occurs when the layer of muscle in the walls of the gastrointestinal tract squeeze in a pattern that propels the food and liquid through the digestive tract. In peristalsis, one part of the muscle contracts while the part directly in front of it relaxes, facilitating the forward movement of the intestinal contents.
Each end of the esophagus has a circular muscle that opens and closes like a drawstring — and at the bottom of the esophagus this muscle (called the lower esophageal sphincter) closes tightly so the corn stays in the stomach. For the corn kernel, it’s a one-way trip with no return ticket.
The stomach
The stomach has a kind of rockstar status when it comes to digestion — that is, it often stands for the whole of the digestive tract. In everyday language, you may say you have a “stomachache” even though your problem could be at a number of different sites in the digestive tract.
True, important digestive work does happen in the stomach. Food that enters the stomach gets aggressively mixed and broken down, with acid and enzymes added to speed up the digestion process. The stomach walls squeeze the food as the gastric juices continue to break down carbohydrates and fats, and they also start breaking down proteins. Your stomach absorbs some fat-soluble substances, such as aspirin and certain types of alcohol.
The corn kernel gets tossed around in the stomach’s acid bath, but even though conditions are harsh, the tough pericarp remains intact. Finally, the kernel is eased out of the stomach when the lower stomach muscle loosens, bringing it to the next part of its journey.
The small intestine
The small intestine is a long and windy tube whose main job is to extract nutrients from your food. It has a velvety lining on the inside with many folds, containing tiny hairlike microvilli that create a huge absorptive area. The small intestine gets first dibs on absorbing most of the food components that nourish the body. Water is also absorbed throughout the length of this part of the digestive tract.
The small intestine has three parts that the corn kernel visits as it moves along:
Duodenum:
The first part of the small intestine immediately below the stomach. This part is where food substances are mixed with different digestive secretions.
Jejunum:
The middle part of the small intestine, making up about two-fifths of its length, where a lot of the nutrient absorption happens.
Ileum:
The bottom part of the small intestine, which is connected to the beginning of the large intestine.
Your pancreas makes digestive enzymes to further break down carbohydrates, fats, and proteins, and delivers them to the duodenum through small tubes called ducts. Furthermore, your liver makes bile and ships it to the gallbladder where it’s stored and concentrated. The bile is released into the small intestine when needed to finish the chemical digestion of fats.
After many of the food components are absorbed (that is, they get the all-clear to pass through the gut barrier), your circulatory system delivers them to other parts of your body for immediate use or storage. For example, your blood carries some sugars, amino acids, glycerol, and some vitamins and salts to the liver. The liver processes some of these items and stores them until they’re needed at other body sites.
Peristalsis moves the corn kernel down through the small intestine’s entire length and onward to the large intestine.
The large intestine and anus
The large intestine (with the colon as its main part) is a beautiful thing. I say this figuratively rather than literally — unless fleshy, squishy, and odorous is your aesthetic. (No judgment.) But the colon really does have its fan club: Neil Pasricha named the colon one of the most awesome things in the original 2010 Book of Awesome (Amy Einhorn Books), for example. And Giulia Enders waxed lyrical about the colon in her popular 2014 book Gut: The Inside Story of Our Body’s Most Underrated Organ (Greystone Books).
The colon is anything but a place for leftovers from the digestive journey. It’s a place of transformation and renewal. Its huge population of microorganisms (refer to Chapter 3) turn undigested fiber into substances that maintain health.
The large intestine is shorter than the small intestine, but it has a bigger diameter. The main parts of the large intestine are as follows:
Cecum:
A pouch located at the junction of the small and large intestines
Ascending colon:
The first tubelike section of the large intestine, which is usually located on the right side of the body and extends upward
Transverse colon:
The middle section of the large intestine, which extends horizontally across the body from right to left
Descending colon:
The section of the colon that extends down from the transverse colon on the left side of the body
Sigmoid colon:
A shorter S-shaped part of the colon, which connects the descending colon to the rectum
Rectum:
The last part of the large intestine, which is a short vertical tube that is the final stop for waste before it passes out of the body through the anus
The appendix is a thin pouch attached to the cecum at the beginning of the large intestine. Even though for many years the appendix was considered to have no special function, more recent investigations show it holds a sample of the gut microbiota that may be useful for repopulating the colon after disturbance by illness or antibiotics.
The intestinal contents continue to move along through peristalsis. Extra water is absorbed into the body through the walls of the large intestine, creating solid waste.
The corn kernel, nearing the end of its journey, moves through all of the parts of the large intestine. Then it exits through the anus, which is an opening surrounded by muscles that relax during the process of defecation. The corn kernel ends up in the toilet, ready to be flushed away and forgotten.
LOOKING CLOSER AT WHAT’S IN YOUR POOP
You produce it every day, but what is your poop made of? Typically, fecal matter is around 75 percent water and 25 percent solids. The solids are a mixture of living and dead microbes as well as undigested carbohydrate, fiber, protein, and fat — and a few inorganic substances such as calcium phosphate and iron phosphate. The bacteria give poop its most distinctive qualities. The brown color comes from bacteria acting on bilirubin, which is an end product from the breakdown of old red blood cells. The odor is caused by chemicals produced by bacteria, including indole and hydrogen sulfide.
What you eat is an important determinant of how your waste appears. If you eat lots of dietary fibers, your poop may appear bigger and softer. Specific things you ingest may also affect its appearance; for example, black licorice, blueberries, Pepto Bismol, or an iron supplement can all make your stool appear black. Chapter 6 explains the difference between normal and abnormal bowel movements.
Recognizing the Essentials about Gut Function
Several important processes help digestion proceed normally: the gut’s nervous system, proper movement of the intestinal contents, and chemical reactions in the gut. Digestive-immune system interactions also occur. This section covers these complex factors that are necessary for producing smooth digestion.
Getting to know your gut’s nervous system
Your central nervous system (CNS) — the brain and spinal cord — gets a lot of attention, but your gut has its own distributed system of nerves called the enteric nervous system (ENS).
The ENS consists of nerves within the walls of your gastrointestinal tract, which control various aspects of digestion. The nerves sense food and have the power to influence how fast the food moves as well as the digestive juices that are produced. The nerves also send signals to influence the actions of your gut muscles as they participate in peristalsis.
The ENS nerves relay many signals to the brain through connections to the CNS, mainly the vagus nerve, allowing signals to flow back and forth. Most of the signals between the gut and brain go in the upward direction, so the brain keeps close track of activities in the gut as sensed by the ENS. Chapter 5 has more information on the gut-brain axis.
Understanding gut motility
Digestion can’t be rushed. Just think about the figurative meaning of the word “digestion” — when you say you’re digesting a piece of information, you’re taking the time to understand it and realize its implications. Time is important for literal digestion too. Even though you can eat quickly, the food takes its own sweet time getting through your digestive tract. If the gut contents move too fast or too slow, digestion goes wrong.
Motility encompasses the mechanisms by which food moves through your digestive tract after the moment of ingestion, including through peristalsis.
One way to measure motility is by observing your gut transit time: the amount of time it takes for a food item to go all the way through your digestive tract. Here are a couple of possible ways to measure gut transit time:
Blue poop challenge:
A 2021 article in the scientific journal
Gut
outlined a new method for measuring gut transit time, which involved baking muffins with a special blue dye, eating one, and timing how long it took to see blue poop in the toilet. The study found the normal range to be anywhere between 14 and 58 hours to see the blue go through your system. After publication of this article, a gut microbiome testing company chimed in with the
#bluepoopchallenge
and invited individuals to test their gut transit time. Soon the challenge was all over social media, bringing gut health into the spotlight for a fleeting moment.
Bristol Stool Scale:
Another rough way to measure motility is to look at the quality or appearance of the stool. A fast gut transit time tends to result in looser stool because the material doesn’t sit in the colon long enough to have the water absorbed. A slow gut transit time tends to result in constipation because the material sits in the colon too long and has so much water extracted that it becomes a hard mass. A chart referred to as the Bristol Stool Scale (refer to
Figure 2-3
), is used clinically to indicate an individual’s stool shape, with seven categories from hardest to softest, as part of assessing digestive health.
Different disorders can arise when motility goes wrong in different parts of the digestive tract. Chapter 7 covers some of these disorders.
