Chapter 18 — Exercises

Three tiers. 🚪 marks work on the threshold concept; 🔄 marks retrieval.

Tier 1 — Recall and Comprehension

R1. State both halves of "the dose makes the poison." Which half does wellness marketing usually lose, and which half does the "it's just calories" argument usually lose?

R2. Give the composition of sucrose and HFCS-55. Why does the difference matter less than it sounds?

R3. Name two facts that argue against HFCS being uniquely harmful — one experimental, one international.

R4. Where is most low-dose fructose cleared, and what happens at high fast doses? Why does this reframe the whole fructose argument?

R5. Give the three reasons the added-versus-natural distinction is real, none of which is about purity.

R6. State the liquid-calorie compensation finding, and give three mechanisms proposed for it.

R7. Where does the sugar–alcohol analogy hold (four points) and where does it break (four points)?

R8. Why can't you starve a tumour by cutting dietary sugar? Give three distinct reasons.

R9. What is documented about the Sugar Research Foundation episode, and what four qualifications does §18.12 attach to the causal claim built on it?

R10. IARC classified aspartame Group 2B while JECFA reaffirmed the ADI. What different question is each body answering?

R11. State the WHO free-sugar recommendation and the AHA added-sugar figures.

Tier 2 — Application

A1. 🚪 Fill the five slots. For each unanswerable question, rewrite it as an answerable one using dose · form · period · population · comparator:

a) "Is sugar bad for you?" b) "Are seed oils inflammatory?" c) "Is red meat carcinogenic?" d) "Is intermittent fasting good for you?" e) "Is coffee healthy?"

(b, c and d are Chapters 19, 26 and 21. Write your versions now; you're building the questions those chapters will answer.)

A2. Which claim is being made? Assign each statement to Claim 1, 2, 3 or 4 from §18.1, and say whether the speaker's evidence would support it:

a) "Cutting sugar helped me lose 15 pounds." b) "Fructose is metabolized in the liver just like alcohol." c) "The AHA says men should cap added sugar at 36 g." d) "Sugar should carry warning labels like cigarettes." e) "Soda taxes reduce purchasing."

A3. Theo's table. His breakdown was: soda 39 g, sweetened coffee 13 g, cereal/bars/yoghurt 11 g, savoury items 9 g, dessert 6 g.

a) What percentage reduction does eliminating soda alone achieve? b) He gives up dessert instead. What percentage does he achieve, and how does that compare with the effort involved? c) He replaces both sodas with diet versions. What has changed and what hasn't, per §18.13? d) ⚠️ He replaces both sodas with 500 mL of orange juice each. Work out what happens.

A4. Label reading. Find three packaged foods in your kitchen that don't taste sweet. For each, record the total sugars, the added sugars if listed, and every ingredient that is a sugar under another name. Which surprised you?

A5. The comparator test. §18.13 says the sweetener question is entirely about the comparator. Give the honest verdict for each substitution:

a) Diet soda replacing regular soda b) Diet soda replacing water c) Stevia in coffee replacing 2 tsp sugar d) A "sugar-free" ultra-processed snack replacing a piece of fruit

A6. 🔄 Run Chapter 17's ten-minute check on this claim, showing each stage:

"Fruit is nature's candy — the fructose still goes straight to your liver and turns into fat. If you're serious about metabolic health, cut the fruit too."

Which minute does it die at, and what is the narrower true version?

Tier 3 — Analysis and Synthesis

S1. 🚪 The threshold, tested against itself. "The dose makes the poison" is presented as resolving category-error questions.

a) Find a case where it fails — a substance where no dose is acceptable, or where the framing actively misleads. b) Does the principle apply to patterns as well as substances? What's the "dose" of a dietary pattern? c) ⚠️ Could this threshold be used to defend anything? What stops it becoming a universal excuse ("it's fine in moderation")?

S2. The isocaloric design. §18.8 and §18.15 both treat isocaloric substitution as the discriminating study design.

a) Explain precisely what it discriminates between. b) Name three practical reasons such trials are hard to run for long enough to settle this. c) If you had unlimited funding, design the trial that would resolve Claim 3. State your primary outcome, duration, comparator and sample. Then say what would still confound it.

S3. The documented-episode test. §18.12 offers a test for distinguishing real industry influence from suppressed-truth rhetoric: "names the year, the journal, the authors, the sponsor, and the archive."

a) Apply it to three claims about industry influence you've encountered. b) ⚠️ Where does the test fail? Construct a case that passes the test and is still misleading. c) Does the test help or hurt when the influence is recent enough that documents aren't public yet?

S4. Reverse causation, three ways. This chapter contains at least three reverse-causation problems: tumour glucose uptake, diet-drink cohorts, and SSB–T2D residual confounding.

a) State each precisely. b) Rank them by how confident you are that reverse causation explains the finding. c) For the one you rank most confidently, what study design would settle it?

S5. The falling-intake problem. US added sugar consumption declined from its early-2000s peak while type 2 diabetes prevalence continued to rise.

a) List five explanations consistent with sugar still mattering. b) List two consistent with it mattering less than claimed. c) ⚠️ Which of your seven can be tested, and how? (An explanation that can't be tested is doing the same work as the suppressed-truth shape, whichever side offers it.)

S6. Steelman both sides. Reread §18.15's table, then do it yourself — without looking — for a different question: should sugar-sweetened beverages be taxed?

Write the strongest version of each position, including the "what would change their mind" row. ⚠️ If you cannot fill that row for the side you disagree with, you have not understood it yet.

🪞 Reflection

M1. Theo's desserts were 8% of his added sugar and the part he'd have given up first. What's your equivalent? — the thing you'd sacrifice because it feels like the indulgence, rather than because it's the quantity.

M2. ⚠️ §18.12 asks you to accept a documented case of industry influence immediately after Chapter 17 taught you to distrust that shape. Did you feel resistance? Which way did it run — toward dismissing the documentation, or toward over-crediting it?

M3. The Project Checkpoint asks you to name one source you're keeping deliberately. Did you find that easy or did it feel like cheating? What does your answer tell you about how you frame dietary change?

M4. 🔄 Both camps in §18.15 would give Theo the same advice. Where else in this book have you seen a loud disagreement about mechanism that made almost no difference to the practical recommendation? Name two, and say why the argument persists anyway.