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Appendix A: Mock Exam

This mock exam has 50 multiple-choice questions that cover all 20 chapters of Gut Check. Plan on about 60 minutes. It works for self-study before a test, for review after you finish the book, or as a class exam that teachers can assign in full or by part.

How to use it:

  • The questions are grouped into five parts that follow the order of the book. Each part covers four chapters.
  • Choose the best answer for each question before you click Show Answer. Many questions ask you to read data, grade a claim with the Hype Meter, or predict what happens next in a pathway, so take your time.
  • Each answer names the chapter it comes from, so you know where to review.
  • The Answer Key at the end lists all 50 answers in one table for quick scoring.

This exam is for learning. It is not medical advice.

Part I: Foundations of the Gut-Brain Axis (Chapters 1 to 4)

Question 1

Which nerve network inside the gut wall mainly controls the lining (secretion and local blood flow) rather than gut movement?

  1. The myenteric plexus
  2. The submucosal plexus
  3. The nodose ganglion
  4. The dorsal motor nucleus of the vagus
Show Answer

The correct answer is B. The submucosal plexus sits just under the lining and mainly works on the mucosa. The myenteric plexus, between the two muscle layers, mainly controls movement. The nodose ganglion and dorsal motor nucleus belong to the vagus pathway, not to the enteric nervous system.

Chapter: Chapter 1: The Brain in Your Belly (and Why That Phrase Is Misleading) Bloom's Level: Remember

Question 2

A researcher places a short piece of animal intestine, with no connection to the brain or spinal cord, in a warm nutrient bath and slips a small soft ball inside. What should she predict?

  1. The wall squeezes behind the ball and relaxes ahead of it, pushing the ball along.
  2. Nothing happens, because every gut movement needs a command from the brain.
  3. The wall twitches at random but cannot move the ball in one direction.
  4. The ball moves only if the vagus nerve is left attached to the piece.
Show Answer

The correct answer is A. The peristaltic reflex is a local enteric circuit: stretch triggers contraction behind the food and relaxation ahead of it. Scientists have watched isolated intestine do this since 1755. The brain and vagus can adjust gut movement, but they are not required for this reflex.

Chapter: Chapter 1: The Brain in Your Belly (and Why That Phrase Is Misleading) Bloom's Level: Apply

Question 3

Two posts appear in your feed. Post 1: "Your gut has its own nervous system that can run digestive reflexes without your brain." Post 2: "Your gut has more neurons than your brain." Which pair of Hype Meter grades fits the evidence in Chapter 1?

  1. Post 1: Strong. Post 2: Strong.
  2. Post 1: Hype. Post 2: Strong.
  3. Post 1: Moderate. Post 2: Preliminary.
  4. Post 1: Strong. Post 2: Hype.
Show Answer

The correct answer is D. Isolated gut segments and Hirschsprung disease give strong evidence that the ENS runs reflexes on its own. But the ENS has about 400 to 600 million neurons, while the brain has about 86 billion, well over a hundred times more. So Post 1 is Strong and Post 2 is Hype.

Chapter: Chapter 1: The Brain in Your Belly (and Why That Phrase Is Misleading) Bloom's Level: Evaluate

Question 4

Enteroendocrine cells in the gut lining sense nutrients and release hormones that help tell you that you are full. Which pair of hormones does Chapter 2 name as satiety signals?

  1. Cortisol and ACTH
  2. Serotonin and dopamine
  3. CCK and GLP-1
  4. Insulin and melatonin
Show Answer

The correct answer is C. Enteroendocrine cells release gut hormones such as CCK and GLP-1, which act as satiety (fullness) signals. Cortisol and ACTH are stress hormones from the HPA axis (Chapter 7). Serotonin and dopamine are neurotransmitters, not the satiety hormones this chapter describes.

Chapter: Chapter 2: The Vagus Highway Bloom's Level: Remember

Question 5

An influencer measures her heart rate variability (HRV) before and after five minutes of humming. Her HRV goes up, and she posts: "Humming reset my vagus nerve and cured my anxiety!" Which critique is strongest?

  1. HRV cannot change in a few minutes, so her device must be broken.
  2. Humming only works through spinal nerves, so the vagus could not be involved.
  3. HRV is an indirect estimate of vagal activity at the heart, and a brief shift does not show a "reset" or a treatment for an anxiety disorder.
  4. She should have measured stomach acid instead, because the vagus nerve does not affect the heart.
Show Answer

The correct answer is C. Small lab studies show that tricks like slow breathing or cold on the face can briefly shift heart rate and HRV. HRV is only an indirect estimate of vagal activity at the heart, and no study in this chapter shows these tricks reset the vagus or treat an anxiety disorder. "Reset" has no scientific meaning here, which is why the claim grades as Hype.

Chapter: Chapter 2: The Vagus Highway Bloom's Level: Analyze

Question 6

A newborn cannot digest human milk oligosaccharides (HMOs). Why do these sugars still matter for the baby's gut?

  1. They feed certain beneficial gut bacteria, such as Bifidobacterium, which helps shape the baby's first microbial community.
  2. They are the main fuel for the baby's brain cells.
  3. They kill all bacteria in the baby's gut so the immune system can develop alone.
  4. They are antibodies that replace the baby's own immune system.
Show Answer

The correct answer is A. HMOs pass through the baby undigested and act as food for certain helpful bacteria such as Bifidobacterium. That is one way breastfeeding shapes the early microbiome. They are sugars, not antibodies, and they feed microbes rather than wiping them out.

Chapter: Chapter 3: Meet the Microbiome Bloom's Level: Understand

Question 7

A video claims: "Bacterial cells outnumber your human cells 10 to 1, so you are only 10% human." Which response best matches Chapter 3?

  1. The claim is right; modern cell counts confirmed the 10 to 1 ratio.
  2. The claim is backwards; human cells outnumber bacterial cells 10 to 1.
  3. The claim is wrong because bacteria live only in the stomach, not the colon.
  4. The old 10 to 1 figure is wrong; a typical adult has roughly 38 trillion bacterial cells and 30 trillion human cells, about 1.3 to 1.
Show Answer

The correct answer is D. The 2016 estimate puts a typical adult at about 38 trillion bacterial cells and 30 trillion human cells, roughly 1.3 to 1. The old "10 to 1" number was never well measured and is wrong. Most gut bacteria live in the colon, not the stomach.

Chapter: Chapter 3: Meet the Microbiome Bloom's Level: Apply

Question 8

Most E. coli in a healthy colon are harmless, yet some E. coli cause serious illness. What best explains this?

  1. Harmless E. coli turn dangerous whenever a person eats sugar.
  2. Different strains of the same species share most genes but differ in some, which can change what they do.
  3. Only E. coli in the stomach are harmful; those in the colon are always safe.
  4. Antibiotics turn commensal E. coli into pathogens by changing their species.
Show Answer

The correct answer is B. A bacterial strain is a genetic variant within a species. Most E. coli strains are commensals, while some strains are pathogens. That is why careful researchers and labels name the strain, not only the species.

Chapter: Chapter 3: Meet the Microbiome Bloom's Level: Understand

Question 9

What are Peyer's patches?

  1. Scar tissue left behind after a Crohn's flare
  2. Groups of pacemaker cells that set the rhythm of gut muscle
  3. Clusters of gut-associated lymphoid tissue that sample what you swallow
  4. Patches of microglia on the surface of the brain
Show Answer

The correct answer is C. Peyer's patches are part of gut-associated lymphoid tissue (GALT), the immune tissue that samples material from the gut. Pacemaker cells in the gut are interstitial cells of Cajal (Chapter 1). Microglia are the brain's own immune cells.

Chapter: Chapter 4: The Immune System as a Sense Organ Bloom's Level: Remember

Question 10

In an animal experiment, researchers cut the vagus nerve and then trigger gut inflammation. The animal still shows some sickness behavior. Which explanation fits Chapter 4?

  1. Sickness behavior is caused only by the vagus nerve, so the cut must have been incomplete.
  2. Sickness behavior comes from the gut itself and never involves the brain.
  3. Cytokines cannot reach the brain at all, so the behavior must be faked.
  4. Cytokines can also signal the brain through circumventricular organs, transport across the blood-brain barrier, and relays from barrier cells.
Show Answer

The correct answer is D. Chapter 4 describes four routes for immune messages to reach the brain: nerves (especially the vagus), circumventricular organs, transport across the blood-brain barrier, and relays from barrier cells. Cutting one route leaves the others. Sickness behavior is a real, brain-driven response, shown experimentally in humans.

Chapter: Chapter 4: The Immune System as a Sense Organ Bloom's Level: Understand

Question 11

A student's report says: "Inflammation is the cause of depression." Which revision best matches the evidence and the Moderate grade in Chapter 4?

  1. Inflammation can contribute to depression in some people, but not every depressed person is inflamed, and depression has many causes.
  2. Inflammation has no connection to mood, so the sentence should be deleted.
  3. Inflammation causes all depression, so anti-inflammatory drugs cure it.
  4. Depression causes inflammation, but inflammation never affects mood.
Show Answer

The correct answer is A. People with depression have higher average inflammation markers, and experimental inflammation lowers mood in healthy adults. But not everyone with depression is inflamed, and an anti-TNF drug did not treat depression overall. That mix is why the claim grades Moderate and needs the words "in some people."

Chapter: Chapter 4: The Immune System as a Sense Organ Bloom's Level: Evaluate

Part II: Chemistry, Stress, and Pain (Chapters 5 to 8)

Question 12

The gut's enterochromaffin cells and the brain's neurons make serotonin with different versions of an enzyme. Which enzyme do the brain's serotonin neurons use?

  1. TPH1
  2. TPH2
  3. The serotonin transporter (SERT)
  4. Kynurenine
Show Answer

The correct answer is B. The brain makes its own serotonin from tryptophan using TPH2. Enterochromaffin cells in the gut use TPH1. SERT clears serotonin after it is released, and kynurenine is a product of the pathway that uses most dietary tryptophan.

Chapter: Chapter 5: Chemical Messengers and the Serotonin Myth Bloom's Level: Remember

Question 13

A blood test shows that most serotonin in the bloodstream is stored inside platelets. A student concludes, "A blood serotonin test tells us how much serotonin is in the brain." What is the main flaw?

  1. Platelets carry serotonin straight into the brain, so the test would overestimate it.
  2. The brain does not use serotonin, so there is nothing to measure.
  3. Blood serotonin comes from the brain, so the test measures only brain levels.
  4. Blood serotonin comes mostly from the gut and cannot cross the blood-brain barrier; the brain makes its own supply.
Show Answer

The correct answer is D. More than 90% of the body's serotonin is made in the gut, and much of it is stored in platelets. Gut serotonin does not cross the blood-brain barrier, so the brain makes its own from tryptophan. A blood level therefore says little about brain serotonin.

Chapter: Chapter 5: Chemical Messengers and the Serotonin Myth Bloom's Level: Analyze

Question 14

In people, the three main short-chain fatty acids end up in different places. Why does acetate, rather than butyrate, reach most of the body?

  1. Acetate is made in the brain, not the colon.
  2. Butyrate is destroyed by stomach acid before it reaches the colon.
  3. The colon lining takes up most butyrate and the liver takes up most propionate, so acetate is the one that travels on.
  4. Butyrate cannot be made from fiber, only from meat.
Show Answer

The correct answer is C. In people, colonocytes take up butyrate as fuel and the liver takes up propionate. Acetate, usually the most abundant SCFA, is left to reach the rest of the body. All three are made in the colon when microbes ferment fiber.

Chapter: Chapter 6: Fiber, Fatty Acids, and the Blood-Brain Barrier Bloom's Level: Understand

Question 15

Sam eats a big bowl of beans. Which sequence best predicts what happens to the fiber?

  1. It passes through the small intestine undigested; in the colon (mostly the cecum and ascending colon), bacteria ferment it into gas and short-chain fatty acids.
  2. Stomach enzymes break it into glucose, which is absorbed in the small intestine.
  3. It is absorbed whole in the small intestine and carried to the brain.
  4. Bacteria in the mouth ferment it into butyrate before it is swallowed.
Show Answer

The correct answer is A. Dietary fiber is the part of plant food that human enzymes cannot digest, so it reaches the colon intact. There, microbes ferment it, mostly in the cecum and ascending colon, producing gas and SCFAs (acetate, propionate, and butyrate).

Chapter: Chapter 6: Fiber, Fatty Acids, and the Blood-Brain Barrier Bloom's Level: Apply

Question 16

Why does Chapter 6 grade "Short-chain fatty acids protect the human blood-brain barrier" as Preliminary rather than Moderate?

  1. Because SCFAs have been proven to harm the blood-brain barrier in large human trials.
  2. Because the barrier findings come from germ-free mice, and the one small human trial (66 men, one week) measured the cortisol response to stress, not the blood-brain barrier.
  3. Because SCFAs are not made by gut bacteria.
  4. Because no animal study has ever looked at SCFAs and the brain.
Show Answer

The correct answer is B. In germ-free mice, the barrier is leakier and microglia are immature, and microbes or butyrate partly reverse this. No human study has shown a change in barrier permeability. The only human trial was small, short, and measured something else, so the grade stays Preliminary.

Chapter: Chapter 6: Fiber, Fatty Acids, and the Blood-Brain Barrier Bloom's Level: Evaluate

Question 17

Imagine an experimental drug that blocks the receptors CRH acts on in the pituitary gland. If someone taking it faced a stressful event, what would you predict for the HPA axis?

  1. More ACTH and more cortisol, because the pituitary would work harder
  2. No change, because CRH acts only on the colon
  3. Less ACTH release and so a smaller rise in cortisol
  4. Higher CRH from the adrenal glands, which would replace cortisol
Show Answer

The correct answer is C. In the HPA axis, CRH from the hypothalamus triggers ACTH from the pituitary, and ACTH triggers cortisol from the adrenal cortex. Blocking the CRH signal at the pituitary would weaken the next two steps. CRH comes from the hypothalamus, not the adrenal glands.

Chapter: Chapter 7: Stress and the Gut Bloom's Level: Apply

Question 18

Small human experiments show that public-speaking stress can make the small intestine more permeable. Which cell type does Chapter 7 link to this effect?

  1. Interstitial cells of Cajal
  2. Enterochromaffin cells
  3. Red blood cells
  4. Mast cells
Show Answer

The correct answer is D. Chapter 7 explains that stress makes the small intestine more permeable through mast cells, immune cells that release chemical signals. Mast cells near nerves are also linked to IBS pain. Enterochromaffin cells make serotonin, and interstitial cells of Cajal set gut rhythm.

Chapter: Chapter 7: Stress and the Gut Bloom's Level: Understand

Question 19

After a gut pain signal reaches the thalamus, which cortex areas does Chapter 8 name as helping turn it into a pain experience?

  1. The insula and the anterior cingulate cortex
  2. The primary visual cortex and the cerebellum
  3. The nodose ganglion and the dorsal root ganglion
  4. The hypothalamus and the adrenal cortex
Show Answer

The correct answer is A. The pathway runs from nociceptors in the gut wall to the dorsal root ganglion, the dorsal horn, the thalamus, and cortex areas including the insula and anterior cingulate cortex. Ganglia are clusters of nerve cell bodies outside the brain, not cortex areas.

Chapter: Chapter 8: Pain, Sensitivity, and the Gut Bloom's Level: Remember

Question 20

A person has an inflamed internal organ, but she feels the ache in a patch of skin and muscle somewhere else. What best explains this?

  1. The inflammation has spread through the blood to that patch of skin.
  2. Sensory fibers from the organ enter the spinal cord at the same level as fibers from that body surface, so the brain misreads where the signal came from.
  3. The vagus nerve carries all organ pain straight to the skin.
  4. Her pain is imagined, because real organ pain is always felt exactly at the organ.
Show Answer

The correct answer is B. This is referred pain. Gut sensory nerves are sparse and share spinal relay neurons with nerves from the body surface, so the brain can place the pain in the wrong spot. Referred pain is real, not imagined.

Chapter: Chapter 8: Pain, Sensitivity, and the Gut Bloom's Level: Understand

Question 21

Months after a gut infection has fully healed, tests show no remaining inflammation, yet Jordan still has high pain sensitivity that has spread to nearby areas. Which description fits best?

  1. Peripheral sensitization, because the gut tissue is still inflamed
  2. Normal nociception, because pain always matches tissue damage
  3. Imagined pain, because the tests are normal
  4. Central sensitization, a real and reversible turning up of pain signals in the spinal cord and brain
Show Answer

The correct answer is D. Peripheral sensitization happens at the gut, usually because of ongoing inflammation, which Jordan no longer has. Central sensitization turns up signals in the spinal cord and brain and can outlast the original injury. Chapter 8 stresses that it is real and reversible, and normal tests never mean imaginary pain.

Chapter: Chapter 8: Pain, Sensitivity, and the Gut Bloom's Level: Apply

Part III: Gut Conditions (Chapters 9 to 12)

Question 22

How does a JAK inhibitor differ from an anti-TNF biologic in treating IBD?

  1. A JAK inhibitor is an antibody given by infusion; an anti-TNF is a vitamin.
  2. A JAK inhibitor is a steroid used only as a short-term bridge.
  3. A JAK inhibitor is a small-molecule pill that blocks enzymes inside immune cells that relay signals from many cytokines; an anti-TNF is a biologic that targets one cytokine.
  4. They are the same medicine sold under two names.
Show Answer

The correct answer is C. JAK inhibitors such as tofacitinib and upadacitinib are pills that block Janus kinase enzymes inside immune cells, affecting signals from many cytokines at once. Anti-TNF medicines are biologic therapies that block one cytokine, TNF. Corticosteroids are the short-term bridge.

Chapter: Chapter 9: Inflammatory Bowel Disease: Ulcerative Colitis and Crohn's Bloom's Level: Understand

Question 23

A teen's colonoscopy shows patches of inflammation in the end of the small intestine and in the colon, with normal areas in between. The inflammation goes through the full thickness of the wall, and there is a fistula. Which diagnosis fits best?

  1. Crohn's disease
  2. Ulcerative colitis
  3. Irritable bowel syndrome
  4. Lactose intolerance
Show Answer

The correct answer is A. Crohn's disease can affect any part of the gut, in patches, with transmural inflammation that can cause strictures, fistulas, and abscesses. Ulcerative colitis affects only the colon and rectum, continuously, in the inner layers. IBS and lactose intolerance do not cause visible inflammation.

Chapter: Chapter 9: Inflammatory Bowel Disease: Ulcerative Colitis and Crohn's Bloom's Level: Apply

Question 24

Four weeks after starting a new medicine, Riya feels much better, but her fecal calprotectin is still high. What is the best interpretation?

  1. The test must be wrong, because feeling better means the inflammation is gone.
  2. Inflammation may still be present, since symptoms can improve before the lining heals, so mucosal healing is the goal to check.
  3. High calprotectin means she has IBS now instead of IBD.
  4. She should stop her medicine, because she has reached remission.
Show Answer

The correct answer is B. Fecal calprotectin acts like a smoke detector for gut inflammation. Symptoms can improve before inflammation is gone, which is why the modern goal is mucosal healing. Decisions about medicine are made with the care team, and maintenance treatment usually continues during remission.

Chapter: Chapter 9: Inflammatory Bowel Disease: Ulcerative Colitis and Crohn's Bloom's Level: Analyze

Question 25

Theo, 19, has had belly pain about 3 days a month (not continuous) for 8 months, linked to changes in his bowel habits. He has no alarm features, and all other requirements of both versions are met. Which statement is correct?

  1. He meets Rome IV but not Rome V.
  2. He meets both Rome IV and Rome V.
  3. He meets Rome V but not Rome IV, because Rome IV requires pain at least 1 day a week.
  4. He meets neither, because IBS requires daily pain.
Show Answer

The correct answer is C. Rome IV requires pain at least 1 day a week on average. Rome V counts pain or discomfort at least 3 days a month, as long as it is not continuous. That change is one reason Rome V counts more people as having IBS.

Chapter: Chapter 10: IBS and Disorders of Gut-Brain Interaction Bloom's Level: Apply

Question 26

About what share of people develop IBS in the year after a gut infection, according to Chapter 10?

  1. About 10%
  2. About 50%
  3. About 90%
  4. Almost no one
Show Answer

The correct answer is A. About 10% of people develop post-infection IBS in the year after a gut infection. That makes infection one known trigger, though most people who get a gut infection do not go on to develop IBS.

Chapter: Chapter 10: IBS and Disorders of Gut-Brain Interaction Bloom's Level: Remember

Question 27

A relative says, "IBS is just anxiety." Which evidence from Chapter 10 best shows this claim is Hype?

  1. IBS trials have a placebo response of about 27%, so IBS is imaginary.
  2. Anxiety symptoms are never seen in people with IBS.
  3. IBS damages the bowel and causes cancer, so it cannot be anxiety.
  4. A 2019 meta-analysis found a diagnosed anxiety disorder in about 23% of people with IBS, so most don't have one, and IBS involves measurable changes in gut sensitivity.
Show Answer

The correct answer is D. Anxiety and depression symptoms are more common in IBS, but a diagnosed anxiety disorder appears in only about 23%. IBS also involves measurable changes in gut sensitivity and gut-brain signaling. IBS does not damage the bowel or cause cancer, and a placebo response does not mean a condition is imaginary.

Chapter: Chapter 10: IBS and Disorders of Gut-Brain Interaction Bloom's Level: Evaluate

Question 28

Which description of the 988 Suicide & Crisis Lifeline matches Chapter 11?

  1. It is only for adults and must be booked a week ahead.
  2. It is free, confidential, available 24/7, and can be reached by call, text, or chat.
  3. It charges a fee unless a doctor makes a referral.
  4. It is open only during school hours.
Show Answer

The correct answer is B. Chapter 11 describes 988 as free, confidential, and available 24/7 by call, text, or chat in the US. Getting help is part of good gut care, and reaching out early is a strength, not a failure.

Chapter: Chapter 11: Anxiety, Depression, and the Gut Bloom's Level: Remember

Question 29

In 2016, researchers moved gut microbes from people with major depression into rats or germ-free mice, and the animals showed depression-like behavior. A post says this "proves gut bacteria cause depression in people." Which evaluation is best?

  1. Strong: animal transfer studies are the highest level of evidence.
  2. Hype: the studies were never done.
  3. Preliminary: rodent behavior is not human depression, and human microbiome studies are snapshots that cannot show direction.
  4. Moderate: because the result happened in two species, it is proven in humans.
Show Answer

The correct answer is C. These transfer studies show that microbes can change rodent behavior, which is reasonably supported. But depression-like behavior in rodents is not human depression, and human studies only show that people with depression have somewhat different bacteria at one point in time. That is why the human claim grades Preliminary.

Chapter: Chapter 11: Anxiety, Depression, and the Gut Bloom's Level: Evaluate

Question 30

Which blood test does Chapter 12 describe as a main first step in testing for celiac disease?

  1. A zonulin test
  2. A fecal calprotectin test
  3. An IgE skin-prick test
  4. A tTG antibody test
Show Answer

The correct answer is D. Celiac diagnosis uses a tTG antibody blood test and, for most people, a small bowel biopsy. IgE tests relate to food allergy, calprotectin flags intestinal inflammation, and commercial zonulin tests do not reliably measure zonulin.

Chapter: Chapter 12: Celiac Disease and Food Reactions Bloom's Level: Remember

Question 31

Celiac disease affects about 1 in 100 people worldwide. In a high school of 1,000 students, about how many would you expect to have it?

  1. About 1
  2. About 10
  3. About 100
  4. About 300
Show Answer

The correct answer is B. One in 100 is 1%, and 1% of 1,000 is 10. Many of those students might not know yet, which is one reason testing matters when symptoms suggest celiac disease. Testing should happen before going gluten-free, because the diet can make tests falsely negative.

Chapter: Chapter 12: Celiac Disease and Food Reactions Bloom's Level: Apply

Question 32

Why do some people with celiac disease become lactose intolerant until their small intestine heals?

  1. Damage to the brush border reduces lactase, the enzyme that breaks down milk sugar.
  2. Gluten and lactose are the same molecule.
  3. The gluten-free diet removes all lactase from the body.
  4. Celiac disease creates an IgE allergy to milk protein.
Show Answer

The correct answer is A. Lactase sits on the brush border formed by microvilli. When celiac disease damages the lining, less lactase is available, so lactose is harder to digest. As the lining heals on a gluten-free diet, this often improves.

Chapter: Chapter 12: Celiac Disease and Food Reactions Bloom's Level: Understand

Part IV: Brain Conditions, Food, and Supplements (Chapters 13 to 16)

Question 33

A 2017 study gave microbiota transfer to 18 autistic children with no placebo group. A 2024 trial randomly gave 103 autistic children either a transplant or a placebo. Why is the 2024 trial better at testing whether the treatment works?

  1. It was done in mice, which removes human bias.
  2. It gave every child the treatment, so no one missed out.
  3. It was larger and compared the treatment with a placebo, so improvement from other causes shows up in both groups.
  4. It measured only parent opinions, which are the most accurate measure.
Show Answer

The correct answer is C. Open-label studies without a comparison group cannot separate a treatment effect from expectation, time, or other care. A randomized, placebo-controlled trial lets both groups improve for those reasons, so any extra benefit can be seen. In 2024, the trial found no significant difference from placebo on its main behavior measure.

Chapter: Chapter 13: Autism, ADHD, and the Gut Bloom's Level: Analyze

Question 34

An autistic 10-year-old who speaks few words starts pressing on his belly, sleeping poorly, and getting upset at meals. Based on Chapter 13, what is the best first step?

  1. Treat the behavior as part of autism that needs no medical check.
  2. Start a strict elimination diet found online.
  3. Assume that changing his gut bacteria will change his autism.
  4. Consider that he may be in pain, for example from constipation, and get standard, respectful medical care.
Show Answer

The correct answer is D. Communication and interoception differences can make gut pain harder to recognize, so behavior changes may be a sign that something hurts. GI symptoms such as constipation are more common in autistic children and deserve standard care. Treating the pain is separate from autism itself, which is not a disease to fix.

Chapter: Chapter 13: Autism, ADHD, and the Gut Bloom's Level: Apply

Question 35

Which two hallmarks does Chapter 14 describe in the brain in Alzheimer's disease?

  1. Lewy bodies and loss of dopamine neurons
  2. Amyloid beta plaques and tau tangles
  3. Villous atrophy and gluten ataxia
  4. Mast cells and leaky tight junctions
Show Answer

The correct answer is B. Alzheimer's disease involves amyloid beta plaques and tau tangles. Lewy bodies and loss of dopamine neurons are features of Parkinson's disease. Gut microbe research in Alzheimer's is very early.

Chapter: Chapter 14: Parkinson's, Alzheimer's, and the Gut Bloom's Level: Remember

Question 36

Human autopsies show Lewy pathology early in the vagus nucleus, constipation can come years before diagnosis, and mice show alpha-synuclein can travel from gut to brain along the vagus nerve. But human vagotomy studies are mixed. Which overall verdict on "Parkinson's starts in the gut" fits Chapter 14?

  1. Moderate, as a hypothesis for some patients, because human evidence is mostly correlation
  2. Strong, because mouse studies prove it for every patient
  3. Hype, because the gut has nothing to do with Parkinson's
  4. Strong, because removing the appendix prevents Parkinson's
Show Answer

The correct answer is A. Several lines of evidence point the same way, but human data are mostly correlational, and the gut-first idea may fit only some patients (the gut-first and brain-first subtypes). Appendix removal shows no overall link with Parkinson's in meta-analyses. Moderate as a hypothesis is the honest grade.

Chapter: Chapter 14: Parkinson's, Alzheimer's, and the Gut Bloom's Level: Evaluate

Question 37

An observational study finds a steady pattern: each extra daily serving of ultra-processed food goes with slightly more depression symptoms. What does this dose-response pattern add?

  1. It proves ultra-processed food causes depression.
  2. It shows the link is pure chance.
  3. It shows depression causes people to eat ultra-processed food.
  4. It makes a causal story more believable, but it is not proof, since a confounder could rise in the same steps.
Show Answer

The correct answer is D. A dose-response relationship is what you would expect if an exposure really mattered, so it strengthens a causal story. But money, stress, or existing low mood could rise along with the exposure and create the same pattern. Only well-designed trials can test cause directly.

Chapter: Chapter 15: Food and Mood Bloom's Level: Understand

Question 38

In 2024, 13.7% of US households were food insecure. Why does this fact matter for food and mood research?

  1. It shows that food has no effect on mood.
  2. It proves that ultra-processed food causes food insecurity.
  3. Healthy eating is not equally easy for everyone, and money and stress can affect both diet and mood, confounding observational links.
  4. It means diet should replace treatment for depression.
Show Answer

The correct answer is C. Food insecurity means some families cannot reliably get enough food, let alone choose a particular diet. Money and stress can shape both what people eat and how they feel, so they can create links that look causal. Diet never replaces treatment for depression.

Chapter: Chapter 15: Food and Mood Bloom's Level: Understand

Question 39

What does Chapter 16 say about the word "psychobiotic"?

  1. It is an FDA-approved category of mood medicines.
  2. It is a research term from 2013, not an approved category.
  3. It is a legal term for any probiotic sold in a pharmacy.
  4. It means a probiotic proven to cure depression.
Show Answer

The correct answer is B. "Psychobiotic" was coined as a research term in 2013 for microbes that might benefit mental health. It is not an approved category. In the US, most probiotics are dietary supplements, which do not need FDA approval before sale and cannot claim to treat disease.

Chapter: Chapter 16: Probiotics, Prebiotics, and "Psychobiotics" Bloom's Level: Remember

Question 40

Two probiotic products sit on a shelf. Product X has 50 billion CFU of a strain that has never been tested for anything. Product Y has 5 billion CFU of a named strain that was tested in a trial for the condition it targets. Which is better supported, and why?

  1. Product Y, because what matters is the tested strain, at the tested dose, for the tested condition
  2. Product X, because more CFU always means a bigger benefit
  3. Product X, because all probiotics are basically the same
  4. Neither, because CFU counts only dead bacteria
Show Answer

The correct answer is A. Probiotic effects are strain specific, and more CFU is not automatically better. The best evidence is for a tested strain at the tested dose for the tested condition, counted at the end of shelf life. CFU counts live microbes, not dead ones.

Chapter: Chapter 16: Probiotics, Prebiotics, and "Psychobiotics" Bloom's Level: Apply

Question 41

A probiotic trial in 30 people measured 12 different outcomes. Its main outcome, chosen in advance, did not change, but one other outcome did. The press release reports only that one. What is the best conclusion?

  1. The probiotic is proven to work, because one result was significant.
  2. The trial was larger than most, so every result is reliable.
  3. With many outcomes measured, one positive result could be chance, and the primary outcome set in advance did not improve.
  4. Primary outcomes do not matter once a trial is published.
Show Answer

The correct answer is C. A primary outcome set in advance protects against picking whichever result looks good. In a small trial that measured many outcomes, one positive result can easily happen by chance. Chapter 16 says to be wary of exactly this pattern.

Chapter: Chapter 16: Probiotics, Prebiotics, and "Psychobiotics" Bloom's Level: Analyze

Part V: Treatments, Daily Life, and Reading Claims (Chapters 17 to 20)

Question 42

In July 2025, the FDA approved implanted vagus nerve stimulation for which additional condition?

  1. Crohn's disease
  2. Anxiety
  3. Irritable bowel syndrome
  4. Rheumatoid arthritis
Show Answer

The correct answer is D. Implanted VNS is FDA approved for drug-resistant partial-onset epilepsy (1997, add-on), treatment-resistant depression in adults (2005, add-on), as the Vivistim System, arm-movement rehabilitation after stroke (August 27, 2021), and, as the SetPoint System, moderate to severe rheumatoid arthritis in adults (July 30, 2025). It is not approved for Crohn's disease, IBS, or anxiety.

Chapter: Chapter 17: Medicine for the Gut-Brain Axis Bloom's Level: Remember

Question 43

A family reads about Vowst and asks whether it is approved to treat their teenager's ulcerative colitis. What is the accurate answer?

  1. Yes, Vowst is approved for any gut disease caused by microbes.
  2. No, Vowst is approved only to prevent recurrent C. diff in adults (18 and older) after antibiotics; FMT for ulcerative colitis remains experimental.
  3. Yes, because FDA approval for one condition covers related conditions.
  4. No, because Vowst has not been approved for anything.
Show Answer

The correct answer is B. Vowst (April 26, 2023) is approved for one specific use: preventing recurrence of C. diff infection in adults after antibiotic treatment. FDA approval is always for a specific use, so it does not extend to ulcerative colitis. FMT for ulcerative colitis, Crohn's, autism, and Parkinson's remains experimental.

Chapter: Chapter 17: Medicine for the Gut-Brain Axis Bloom's Level: Apply

Question 44

According to Chapter 18, about how many US high school students got 8 hours of sleep on school nights in 2025?

  1. About 1 in 4
  2. About 3 in 4
  3. About 9 in 10
  4. Almost all of them
Show Answer

The correct answer is A. Only about 1 in 4 US high school students got 8 hours on school nights in 2025, even though teens need 8 to 10 hours per 24 hours. Puberty also shifts teen sleep timing up to 2 hours later.

Chapter: Chapter 18: Sleep, Exercise, and Therapy Bloom's Level: Remember

Question 45

Light mainly sets the brain's master clock. According to Chapter 18, which cue mainly helps set the rhythm inside the gut?

  1. The phase of the moon
  2. Room temperature
  3. Meal timing
  4. Heart rate variability
Show Answer

The correct answer is C. The body has two main timing cues: light, which sets the brain's master clock, and meals, which help set the rhythm inside the gut. Gut microbes also rise and fall on a daily schedule set largely by when you eat.

Chapter: Chapter 18: Sleep, Exercise, and Therapy Bloom's Level: Understand

Question 46

In the 2025 CDC survey described in Chapter 19, what share of US high school students reported persistent sadness or hopelessness?

  1. About 3%
  2. About 10%
  3. About 70%
  4. About 33%
Show Answer

The correct answer is D. In 2025, 33.3% of US high school students reported persistent sadness or hopelessness. Stigma is a major barrier to getting mental health help, especially for young people and minority groups.

Chapter: Chapter 19: Culture, Food, Family, and Stigma Bloom's Level: Remember

Question 47

Maya, 15, has Crohn's disease. She needs to use the restroom without asking each time and needs extra time to make up tests she misses during flares. Which school tool is designed for this?

  1. A 504 plan
  2. A permission slip signed each morning
  3. A peer support group
  4. A low-FODMAP diet plan
Show Answer

The correct answer is A. A 504 plan is a written plan, made by the school with the student and family, that lists accommodations a student with a disability needs for equal access to education. Peer support is valuable too, but it does not set formal school accommodations.

Chapter: Chapter 19: Culture, Food, Family, and Stigma Bloom's Level: Understand

Question 48

A supplement trial reports a side effect in 2 of 1,000 people on placebo and 4 of 1,000 people on the supplement. A headline says the supplement "doubles your risk." What is the absolute risk difference?

  1. About 50 extra cases per 1,000 people
  2. About 2 extra cases per 1,000 people (0.2 percentage points)
  3. About 200 extra cases per 1,000 people
  4. There is no difference, because both numbers are small
Show Answer

The correct answer is B. The relative risk is 4 divided by 2, so "doubles" is technically true. The absolute difference is 4 minus 2, or 2 extra cases per 1,000 people (0.2 percentage points). Only together do the two numbers tell the whole story.

Chapter: Chapter 20: Be Your Own Scientist: Reading Health Claims Bloom's Level: Apply

Question 49

A treatment cuts the chance that an infection comes back from 30% to 10%. What is the number needed to treat (NNT)?

  1. About 2
  2. About 3
  3. About 5
  4. About 20
Show Answer

The correct answer is C. The absolute risk difference is 30% minus 10%, or 0.20. The NNT is 1 divided by 0.20, which is 5. So about 5 people need the treatment for one extra person to avoid a recurrence.

Chapter: Chapter 20: Be Your Own Scientist: Reading Health Claims Bloom's Level: Apply

Question 50

A study of a gut supplement was paid for by the company that sells it. According to Chapter 20, how should a careful reader treat this?

  1. Ignore the funding, because peer review removes all bias.
  2. Reject the study automatically, because company-funded studies are always false.
  3. Assume the results are stronger, because companies run the best trials.
  4. Treat it as a reason to look harder at the design and numbers, since industry sponsorship is linked to more favorable results.
Show Answer

The correct answer is D. A 2017 Cochrane review found that studies sponsored by the maker more often reported favorable results and conclusions. Chapter 20 says this is a reason to look harder, not a reason to dismiss a study automatically. Peer review is a quality check, not a guarantee.

Chapter: Chapter 20: Be Your Own Scientist: Reading Health Claims Bloom's Level: Understand

Answer Key

Question Answer Chapter
1 B Chapter 1: The Brain in Your Belly (and Why That Phrase Is Misleading)
2 A Chapter 1: The Brain in Your Belly (and Why That Phrase Is Misleading)
3 D Chapter 1: The Brain in Your Belly (and Why That Phrase Is Misleading)
4 C Chapter 2: The Vagus Highway
5 C Chapter 2: The Vagus Highway
6 A Chapter 3: Meet the Microbiome
7 D Chapter 3: Meet the Microbiome
8 B Chapter 3: Meet the Microbiome
9 C Chapter 4: The Immune System as a Sense Organ
10 D Chapter 4: The Immune System as a Sense Organ
11 A Chapter 4: The Immune System as a Sense Organ
12 B Chapter 5: Chemical Messengers and the Serotonin Myth
13 D Chapter 5: Chemical Messengers and the Serotonin Myth
14 C Chapter 6: Fiber, Fatty Acids, and the Blood-Brain Barrier
15 A Chapter 6: Fiber, Fatty Acids, and the Blood-Brain Barrier
16 B Chapter 6: Fiber, Fatty Acids, and the Blood-Brain Barrier
17 C Chapter 7: Stress and the Gut
18 D Chapter 7: Stress and the Gut
19 A Chapter 8: Pain, Sensitivity, and the Gut
20 B Chapter 8: Pain, Sensitivity, and the Gut
21 D Chapter 8: Pain, Sensitivity, and the Gut
22 C Chapter 9: Inflammatory Bowel Disease: Ulcerative Colitis and Crohn's
23 A Chapter 9: Inflammatory Bowel Disease: Ulcerative Colitis and Crohn's
24 B Chapter 9: Inflammatory Bowel Disease: Ulcerative Colitis and Crohn's
25 C Chapter 10: IBS and Disorders of Gut-Brain Interaction
26 A Chapter 10: IBS and Disorders of Gut-Brain Interaction
27 D Chapter 10: IBS and Disorders of Gut-Brain Interaction
28 B Chapter 11: Anxiety, Depression, and the Gut
29 C Chapter 11: Anxiety, Depression, and the Gut
30 D Chapter 12: Celiac Disease and Food Reactions
31 B Chapter 12: Celiac Disease and Food Reactions
32 A Chapter 12: Celiac Disease and Food Reactions
33 C Chapter 13: Autism, ADHD, and the Gut
34 D Chapter 13: Autism, ADHD, and the Gut
35 B Chapter 14: Parkinson's, Alzheimer's, and the Gut
36 A Chapter 14: Parkinson's, Alzheimer's, and the Gut
37 D Chapter 15: Food and Mood
38 C Chapter 15: Food and Mood
39 B Chapter 16: Probiotics, Prebiotics, and "Psychobiotics"
40 A Chapter 16: Probiotics, Prebiotics, and "Psychobiotics"
41 C Chapter 16: Probiotics, Prebiotics, and "Psychobiotics"
42 D Chapter 17: Medicine for the Gut-Brain Axis
43 B Chapter 17: Medicine for the Gut-Brain Axis
44 A Chapter 18: Sleep, Exercise, and Therapy
45 C Chapter 18: Sleep, Exercise, and Therapy
46 D Chapter 19: Culture, Food, Family, and Stigma
47 A Chapter 19: Culture, Food, Family, and Stigma
48 B Chapter 20: Be Your Own Scientist: Reading Health Claims
49 C Chapter 20: Be Your Own Scientist: Reading Health Claims
50 D Chapter 20: Be Your Own Scientist: Reading Health Claims