List of Chapters

Each chapter has a MicroSim, a fictional At the Bedside case, Hype Meter grades, Your Gut Check practice, 12 exercises, a 10-question quiz, and references. Chapters list their prerequisites at the top.

Part I. Two Nervous Systems, One Body

• Chapter 1: The Brain in Your Belly (and Why That Phrase Is Misleading): Meet the enteric nervous system, the neuron network in your gut wall that moves food on its own, and learn the Hype Meter for grading gut-brain claims. (Quiz · References)

• Chapter 2: The Vagus Highway: How the vagus nerve, spinal nerves, and gut hormone cells carry messages between gut and brainstem, and why most vagus traffic runs upward. (Quiz · References)

• Chapter 3: Meet the Microbiome: Meet the trillions of microbes in your gut: how many there are, how they settle in at birth, how antibiotics shake them up, and how scientists study them. (Quiz · References)

• Chapter 4: The Immune System as a Sense Organ: How the gut's immune system senses microbes, sends cytokine messages to the brain, and creates the tired, low feeling of sickness behavior. (Quiz · References)

Part II. How the Signals Travel

• Chapter 5: Chemical Messengers and the Serotonin Myth: Most of your serotonin is made in your gut, but it never reaches your brain. Learn where serotonin goes, what SSRIs do, and what gut microbes really make. (Quiz · References)

• Chapter 6: Fiber, Fatty Acids, and the Blood-Brain Barrier: Follow fiber from your plate to the microbes in your colon, meet the short-chain fatty acids they make, and sort real gut-barrier science from leaky gut hype. (Quiz · References)

• Chapter 7: Stress and the Gut: Learn how the HPA axis and fight-or-flight system turn stress into real changes in gut movement, sensitivity, and barrier function, and what germ-free mice reveal. (Quiz · References)

• Chapter 8: Pain, Sensitivity, and the Gut: Why the same gut stretch can hurt one person and not another: nociceptors, spinal gates, the brain's volume knob, and visceral hypersensitivity. (Quiz · References)

Part III. When the System Goes Wrong

• Chapter 9: Inflammatory Bowel Disease: Ulcerative Colitis and Crohn's: How Crohn's disease and ulcerative colitis work, how doctors find and treat the inflammation, and how IBD connects to energy, mood, and the brain. (Quiz · References)

• Chapter 10: IBS and Disorders of Gut-Brain Interaction: Why IBS is real even when tests are normal, how the Rome criteria work (Rome IV and the new Rome V), and which treatments have good evidence. (Quiz · References)

• Chapter 11: Anxiety, Depression, and the Gut: Why anxiety and depression are more common with gut conditions, how the link runs both ways, and how to tell correlation from cause. (Quiz · References)

• Chapter 12: Celiac Disease and Food Reactions: How celiac disease flattens the villi of the small intestine, how doctors test for it, and how it differs from food allergy, intolerance, and gluten sensitivity. (Quiz · References)

• Chapter 13: Autism, ADHD, and the Gut: What the evidence really says about autism, ADHD, and the gut: real GI symptoms worth treating, diet as a confounder, and why cure claims are hype. (Quiz · References)

• Chapter 14: Parkinson's, Alzheimer's, and the Gut: Why constipation can appear years before Parkinson's, what the gut-first and brain-first ideas predict, and what we really know about Alzheimer's and gut microbes. (Quiz · References)

Part IV. What Can Actually Help

• Chapter 15: Food and Mood: What diet studies can and can't tell us about mood: patterns, ultra-processed food, the SMILES trial, confounding, and why randomized trials matter. (Quiz · References)

• Chapter 16: Probiotics, Prebiotics, and "Psychobiotics": What probiotics, prebiotics, and psychobiotics really are, how they are regulated and when they can be risky, and how to read the trials behind the hype. (Quiz · References)

• Chapter 17: Medicine for the Gut-Brain Axis: Fecal transplants, FDA-approved microbiome medicines, vagus nerve stimulators, and low-dose antidepressants for gut pain: what is approved, for what, and why. (Quiz · References)

• Chapter 18: Sleep, Exercise, and Therapy: How sleep, body clocks, exercise, and brain-gut therapies like CBT and gut-directed hypnotherapy affect gut symptoms, and how to track your own patterns honestly. (Quiz · References)

Part V. Living With It, and Thinking Clearly

• Chapter 19: Culture, Food, Family, and Stigma: How stigma, culture, family, and school shape life with gut and mental health conditions, and how to talk about them accurately and kindly. (Quiz · References)

• Chapter 20: Be Your Own Scientist: Reading Health Claims: Turn the Hype Meter into a full claim-checking method: evidence levels, mouse studies, p-values, risk numbers, funding, ads, and your own research project. (Quiz · References)