Chapter 18 — Self-Check Quiz

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

Questions

1. "The dose makes the poison" has two halves. The half most often lost by wellness marketing is:

• a) Nothing is toxic irrespective of dose
• b) Nothing is safe irrespective of dose, including natural things
• c) All compounds have thresholds
• d) Toxicity is individual

2. Sucrose is:

• a) A monosaccharide identical to glucose
• b) A disaccharide of one glucose and one fructose, cleaved in the small intestine
• c) A polymer of fructose units
• d) Chemically unrelated to HFCS

3. HFCS-55 versus sucrose:

• a) HFCS contains roughly twice the fructose
• b) 55/42 free versus 50/50 bonded — compositionally very similar
• c) HFCS contains no glucose
• d) Sucrose contains no fructose

4. The strongest international argument against HFCS being uniquely responsible for obesity is:

• a) HFCS was banned in Europe
• b) Obesity rose sharply in countries using essentially no HFCS
• c) HFCS is more expensive abroad
• d) Sucrose is more common in the US

5. Agave syrup is:

• a) Fructose-free
• b) Often 70–90% fructose — frequently higher than HFCS
• c) Chemically identical to stevia
• d) A non-nutritive sweetener

6. At low doses, most fructose is:

• a) Absorbed unchanged into the bloodstream
• b) Cleared by the small intestine before reaching the liver
• c) Converted directly to body fat
• d) Excreted in urine

7. The three reasons the added-vs-natural distinction is real are:

• a) Purity, processing, and origin
• b) Dose rate, matrix, and what else comes with it
• c) Molecular structure, absorption site, and insulin response
• d) Cost, availability, and marketing

8. In large cohorts, whole fruit and fruit juice show:

• a) Identical associations with T2D
• b) Whole fruit associated with lower risk, juice with higher
• c) Both associated with higher risk
• d) No measurable association either way

9. The core finding that makes sugar-sweetened beverages distinctive is:

• a) Liquid fructose is metabolized by a different enzyme
• b) People do not compensate for liquid calories by eating less later
• c) SSBs contain more sugar per gram than solid food
• d) SSBs are absorbed in the stomach

10. The verdict on SSBs and weight gain/T2D is ✅ Well supported because:

• a) One very large trial settled it
• b) Mechanism, RCTs, cohorts, meta-analyses and tax natural experiments converge
• c) The WHO says so
• d) The association is very large

11. The sugar–alcohol analogy breaks most importantly because:

• a) Alcohol contains more calories per gram
• b) Ethanol produces acetaldehyde, a direct cellular toxin with no fructose counterpart
• c) Alcohol is not metabolized in the liver
• d) Fructose is not found in nature

12. Chapter 12's alcohol argument had a tool this chapter lacks:

• a) A randomized controlled trial
• b) A Mendelian randomization instrument (ALDH2)
• c) A meta-analysis
• d) A dose-response curve

13. When sugar is swapped for other carbohydrate at matched calories, weight differences:

• a) Increase substantially
• b) Largely disappear
• c) Reverse
• d) Cannot be measured

14. A fact that complicates the simple sugar-causes-diabetes story is:

• a) Diabetes is entirely genetic
• b) US added sugar intake declined from its early-2000s peak while T2D prevalence continued rising
• c) Sugar does not raise blood glucose
• d) T2D rates are falling

15. "Sugar feeds cancer" fails partly because:

• a) Cancer cells do not use glucose
• b) Blood glucose is regulated, and the liver produces it via gluconeogenesis regardless of intake
• c) PET scanning has been discontinued
• d) Tumours prefer fat

16. The rodent sugar-addiction findings depend heavily on:

• a) The strain of rat
• b) An intermittent access schedule
• c) The temperature of the solution
• d) Prior cocaine exposure

17. Addiction-like eating in humans attaches most strongly to:

• a) Pure sugar
• b) Combinations of sugar and fat in ultra-processed forms
• c) Fruit
• d) Dietary protein

18. What is documented about the Sugar Research Foundation episode:

• a) That it fabricated data
• b) That it funded and helped shape an undisclosed 1967 NEJM review downplaying sugar
• c) That it bribed government officials
• d) That it suppressed publication of opposing trials

19. §18.12's test for distinguishing real industry influence from suppressed-truth rhetoric is:

• a) Whether a scientist endorses it
• b) Whether it names the year, journal, authors, sponsor and archive
• c) Whether it appears in a peer-reviewed journal
• d) Whether more than one source reports it

20. IARC's Group 2B classification of aspartame is:

• a) A statement about how dangerous it is at typical intakes
• b) A hazard classification about strength of evidence, not a risk estimate at real doses
• c) A withdrawal of approval
• d) A recommendation to ban it

Answers

1. b) Nothing is safe irrespective of dose. ⚠️ "Natural" buys no exemption — agave is mostly fructose, honey is mostly sugar, and 100% fruit juice delivers a soda-like dose. (The "it's just calories" argument tends to lose the other half's practical force — see Q13's explanation.) §18.5.

2. b) A disaccharide, cleaved in the small intestine. Within minutes. Which is why the sucrose-versus-HFCS distinction largely dissolves before either reaches the liver. §18.2.

3. b) 55/42 free versus 50/50 bonded. Compositionally very close. ⚠️ Controlled comparisons at matched doses generally find no meaningful difference. §18.2.

4. b) Obesity rose in countries using essentially no HFCS — the UK, Australia, Mexico, across Europe. ⚠️ A cause present in one country cannot explain an effect present in all of them. §18.2.

5. b) Often 70–90% fructose. ⚠️ Marketed as the natural alternative and frequently the highest-fructose product in the shop — the cleanest available demonstration of §18.5's second half.

6. b) Cleared by the small intestine. Converted to glucose and organic acids before reaching the liver. ⚠️ At high fast doses, intestinal capacity is exceeded and there is spillover. This is the single most important reframe in the chapter: it converts a categorical question into a dose question, and explains why both camps can be right about different doses. §18.4.

7. b) Dose rate, matrix, and what else comes with it. ⚠️ Not purity. An apple is ~19 g of sugar with 4 g of fiber, water and volume, eaten over minutes; a 500 mL soda is ~53 g in ninety seconds with nothing else. Same molecules, different delivery. §18.3.

8. b) Whole fruit lower, juice higher — in the same cohorts, in the same analyses. ⚠️ Same fruit, same sugars, matrix removed and dose rate increased. The best natural experiment available on the matrix question. (Still observational — Chapter 2's caveats apply.) §18.3.

9. b) People do not compensate for liquid calories. Eat 200 kcal solid and you eat somewhat less later; drink 200 kcal and compensation is close to zero. ⚠️ The mechanism is behavioural, not metabolic — and it's the most robust finding in the chapter. §18.7.

10. b) Five lines of evidence converge. Mechanism, RCTs in children/adolescents, large cohorts, meta-analyses, and SSB-tax purchasing data. ⚠️ Chapter 2's convergence criterion met — methods with non-overlapping weaknesses pointing the same way. ⚠️ Note what the verdict attaches to: a delivery format, not a molecule. §18.7.

11. b) Acetaldehyde has no fructose counterpart. Ethanol's metabolite is a recognized carcinogen that directly damages DNA and membranes (Chapter 12 §12.5). ⚠️ Also: there is no intestinal buffer for ethanol, so the low-dose curves have fundamentally different shapes; and ethanol is psychoactive and causally implicated in injury and traffic death. §18.6.

12. b) A Mendelian randomization instrument. ⚠️ ALDH2 gave Chapter 12 a genetic natural experiment isolating alcohol's causal effect. There is no sugar equivalent — which is a large part of why this debate remains unresolved and the alcohol one increasingly isn't. §18.6.

13. b) Largely disappear. Which points to energy rather than a sugar-specific fattening property. ⚠️ This is much less deflationary than it sounds — "it's just calories" and "it doesn't matter" are different statements, and §18.7 is the difference. §18.8.

14. b) Intake fell while prevalence rose. ⚠️ This should complicate anyone's story, in both directions — and Exercise S5 asks you to generate explanations consistent with sugar still mattering, then check which are testable. §18.9.

15. b) Blood glucose is regulated and the liver makes it. Gluconeogenesis (Chapter 6 §6.5) means blood glucose cannot fall toward zero. Plus: every cell uses glucose, so no selective starvation is available; and high uptake is a consequence of tumour metabolism, not its cause — Chapter 2's reverse causation. ⚠️ The harm is real: restrictive anti-cancer diets during treatment cause weight loss when nutritional status matters most. §18.10.

16. b) An intermittent access schedule. ⚠️ Rats with continuous access largely don't show the pattern — which means the finding is at least as much about the schedule as the substance, and that qualification disappears in every retelling. §18.11.

17. b) Sugar–fat ultra-processed combinations. ⚠️ Nobody binges on sugar cubes. The compulsion described is real; calling it a sugar problem misidentifies it — and that misidentification has a cost (Chapter 34). Chapter 22 handles the actual target. §18.11.

18. b) An undisclosed, industry-shaped 1967 review. Documented by Kearns, Glantz and Schmidt in JAMA Internal Medicine (2016) from recovered internal correspondence. ⚠️ This is real and should make you uncomfortable. What it does not establish is that it single-handedly redirected the field — §18.12 attaches four qualifications. §18.12.

19. b) Year, journal, authors, sponsor, archive. ⚠️ A suppressed-truth claim is unfalsifiable and cites nothing. A documented episode names things you can go and check. This is the hardest lesson in the chapter, because Chapter 17 taught you to distrust exactly the shape this episode wears — and this one is true. §18.12.

20. b) A hazard classification about strength of evidence. ⚠️ IARC asks "could this cause cancer under any circumstances?" JECFA asks "does it, at doses people consume?" Both published in 2023 and were widely reported as contradicting each other. Group 2B also contains aloe vera extract and pickled vegetables. This is Chapter 17 §17.9's BPA structure exactly. §18.13.

Scoring

Two items worth checking regardless of score.

Question 6. ⚠️ If you missed the intestinal clearance point, you'll misread the entire fructose debate as a yes/no question. It isn't one, and that's the finding.

Question 19. ⚠️ If you missed the documented-episode test, reread §18.12. Chapters 19 and 20 both contain industry-influence claims, and you will need to sort them.