Chapter 17 — Self-Check Quiz

20 questions. Answers with explanations at the end. Aim for 16+.

Questions

1. Blood pH in a healthy person is maintained within approximately:

• a) 6.8–7.2
• b) 7.35–7.45
• c) 7.6–8.0
• d) It varies substantially with diet

2. Urine pH changing in response to an "alkaline diet" demonstrates:

• a) That the diet is alkalizing the blood
• b) That the kidneys are excreting the acid load and holding blood pH constant
• c) That the body is detoxifying
• d) Nothing measurable

3. In 2012, the USDA withdrew its ORAC database because:

• a) The measurements were found to be fraudulent
• b) Antioxidant capacity measured in vitro does not predict effects in humans, and the values were being misused in marketing
• c) A superior assay replaced it
• d) Funding was cut

4. A stalk of celery contains ~6 kcal. Its approximate net energy contribution after digestion is:

• a) About −4 kcal
• b) About 0 kcal
• c) About +5.5 kcal
• d) About +6 kcal, since digestion is free

5. The 2014 blood type diet study is described as an unusually clean refutation because it:

• a) Found that none of the diets produced any benefit
• b) Found benefits from some diets that were unrelated to the participants' actual blood type
• c) Was funded independently
• d) Had a very large sample

6. Compared with boiling, microwaving vegetables typically:

• a) Destroys more nutrients due to radiation
• b) Retains more water-soluble vitamins, because of shorter time and less water contact
• c) Has no effect on nutrient content
• d) Makes food mildly radioactive

7. The principal genuine hazard associated with non-stick cookware in normal domestic use is:

• a) Ingesting flakes from a scratched pan
• b) Overheating an empty pan above ~260°C, releasing fumes
• c) PTFE dissolving into acidic foods
• d) There is no hazard of any kind

8. Regarding BPA, the chapter assigns 🟡 rather than a firmer verdict because:

• a) There is no evidence either way
• b) EFSA and the FDA have reached materially different conclusions from the same literature
• c) The mechanism is implausible
• d) It has never been studied in humans

9. "BPA-free" products:

• a) Are guaranteed safer
• b) Often use structurally similar, less-studied replacements such as BPS and BPF
• c) Contain no plastics
• d) Are regulated as medical devices

10. The conceptual problem with "boosting" the immune system is that:

• a) The immune system cannot be affected by nutrition at all
• b) An indiscriminately amplified immune response describes autoimmunity or allergy, not health
• c) Only vaccines affect immunity
• d) The immune system is entirely genetic

11. Which intervention most specifically improves defence against a particular pathogen?

• a) Vitamin C
• b) Elderberry
• c) Vaccination
• d) Zinc lozenges

12. Cooking tomatoes increases the bioavailability of:

• a) Vitamin C
• b) Lycopene
• c) Folate
• d) Vitamin B12

13. Rinsing rice and cooking it in excess water is supported partly because it reduces:

• a) Gluten
• b) Inorganic arsenic
• c) Lectins
• d) Phytic acid exclusively

14. Ginger has its best evidence for:

• a) Weight loss
• b) Nausea and vomiting in pregnancy
• c) Blood pressure
• d) Cognitive function

15. The tell for "restriction as virtue" is:

• a) No dose specified
• b) The difficulty of the protocol is offered as evidence that it works
• c) Moral vocabulary
• d) An unspecified past

16. The tell for "the bundled intervention" is:

• a) Binary language about a continuous variable
• b) Counting the number of things that change at once
• c) A named but undosed mechanism
• d) Unfalsifiability

17. According to §17.1's interlude, the dominant failure mode in nutrition claims is:

• a) Deliberate fabrication of data
• b) Over-extension of a real finding beyond what it can support
• c) Statistical fraud
• d) Translation errors

18. In §17.14's ten-minute check, the most diagnostic single comparison for a non-specialist is:

• a) The number of citations
• b) The gap between the evidence rung supplied and the rung the claim requires
• c) The journal's impact factor
• d) Whether the author has a doctorate

19. §17.12 argues that myths most reliably die when:

• a) They are publicly refuted by experts
• b) A regulator removes the substance, or the harm becomes visible enough to be counted
• c) A celebrity abandons them
• d) A meta-analysis is published

20. The recommended first move when someone you love believes a myth is to:

• a) Explain why it's wrong
• b) Compare it to a better-evidenced alternative rather than debunking it
• c) Send them a study
• d) Say nothing under any circumstances

Answers

1. b) 7.35–7.45. Regulated by the lungs (CO₂, minutes) and kidneys (bicarbonate, hours). ⚠️ Moving outside this range is a medical emergency — acidosis and alkalosis have causes like respiratory failure, sepsis and renal failure. Not breakfast. §17.4.

2. b) The kidneys are doing their job. This is the elegant part: the visible confirmation that adherents cite is precisely the evidence that blood pH is being held constant. The acid load is being excreted, which is the system working as designed. §17.4.

3. b) In vitro antioxidant capacity does not predict human effects, and the values were misused. This is Chapter 13's isolated-nutrient problem arriving from a different direction — a test-tube measurement that generated impressive marketing numbers and no clinical outcomes. §17.3.

4. c) About +5.5 kcal. TEF for a carbohydrate-and-fiber food is ~5–10%, so roughly 0.5 kcal of the 6. Net positive, not negative, not close. The general defence from Chapter 5: convert to calories and compare to one beer. §17.7.

5. b) Benefits unrelated to actual blood type. This isolates the specific claim. The "type A" diet is largely plant-based; the "type O" diet is lower-carbohydrate and higher-protein. Both are reasonable diets and both helped people of every blood type — the diets work as their content predicts, and the blood type contributes nothing. It also explains why adherents report results. §17.8.

6. b) Retains more water-soluble vitamins. Nutrient loss depends on time, temperature and water contact. Boiling scores badly on the third — vitamin C leaches into water you pour away. The myth isn't just wrong, it's backwards. §17.9.

7. b) Overheating an empty pan. Above ~260°C, PTFE can release fumes causing polymer fume fever (transient, flu-like) and these are lethal to pet birds. ⚠️ Intact PTFE at normal cooking temperatures is chemically stable; ingested flakes pass through largely inert. The broader PFAS issue is genuine and much bigger than cookware. §17.9.

8. b) EFSA and the FDA differ materially. EFSA substantially lowered its tolerable daily intake in 2023; the FDA has maintained that current exposures are safe. Two competent bodies, the same literature, different conclusions. That is what 🟡 is for — it is not a hedge, it is an accurate description of the state of knowledge. §17.9.

9. b) BPS and BPF are structurally similar and less studied. ⚠️ "BPA-free" is a label change, not necessarily a safety improvement — and the replacements have thinner safety literatures precisely because they're newer. §17.9.

10. b) It describes autoimmunity or allergy. The immune system is not a dial; it is a calibrated network that must distinguish threat from self. ⚠️ The therapeutic goal in most immune disease is suppression. So the claim isn't merely unsupported — it describes a state you wouldn't want. §17.6.

11. c) Vaccination. By some distance, and it is the only one on the list that improves defence against a specific pathogen. 🟢 Correcting a genuine nutritional deficiency also helps — zinc, vitamin A, vitamin D, protein, iron — but that's Chapter 13's pattern, not "boosting." §17.6.

12. b) Lycopene. Cooking breaks down cell walls and converts lycopene to a more bioavailable form; absorption is higher again with fat present (Chapter 3 §3.4). ✅ Well supported. (It doesn't generalize — vitamin C is heat-labile and declines. Different nutrients, different directions.) §17.10.

13. b) Inorganic arsenic. Rice takes up arsenic more than most crops; inorganic arsenic is a recognized carcinogen. ⚠️ FDA and EFSA guidance exists, with particular attention to infants and young children, for whom rice products can be a large share of intake relative to body weight. §17.10.

14. b) Nausea and vomiting in pregnancy. Included as an option in several clinical guidelines; reasonable evidence also for postoperative and motion-related nausea, more mixed for chemotherapy-induced. 🟢 ⚠️ Discuss dose and formulation with a clinician in pregnancy. §17.10.

15. b) The difficulty is offered as evidence. "It's not easy, but…" — the hardship is presented as though it were data. §17.1.

16. b) Count the changes. ⚠️ More than three and nobody will ever learn which one mattered — including the person selling it. Theo's cleanse changed eight things. §17.1.

17. b) Over-extension. Someone took a real finding and stretched it past what it could carry — which is why only six of the 24 retired claims in the interlude are ❌, and most are 🟠 or 🟡. The productive response is "what's the narrower true version?" rather than "that's nonsense." §17.1.

18. b) The gap between the rung supplied and the rung required. "Prevents cancer" needs rung 6–8; "increases lycopene absorption" needs rung 5. You can assess that gap without reading the study. §17.14, Chapter 2 §2.4.

19. b) Regulation, or harm that becomes visible enough to count. Trans fats died by regulation. Ephedra died after documented deaths and a ban. The eight-glasses rule was definitively debunked in 2002 and is still with us, because nothing forced it out. §17.12.

20. b) Compare rather than debunk. Comparison doesn't require the person to have been wrong — which is what Chapter 11's berberine-versus-fiber table did with Walt. ⚠️ (But triage first: some beliefs — delayed medical treatment, restriction in a child, high-dose vitamin A in pregnancy — need intervening on. Most don't.) §17.13.

Scoring

And one item worth checking regardless of score: question 17. If you got it wrong, reread §17.1's interlude. "What's the narrower true version?" is the most portable question in the chapter, and the one that will still be useful when every verdict here has been superseded.