Chapter 9 — Quiz

Twenty-one questions. Attempt before opening.

Multiple Choice

1. "Saturated" refers to:

  • a) How the fat behaves in your arteries
  • b) The carbon chain carrying its full complement of hydrogen — no double bonds
  • c) How much fat is in the food
  • d) Whether the fat is from an animal
Answer **b.** It's a statement about hydrogen and double bonds. The fact that the word *sounds* like a claim about physiology has done a remarkable amount of rhetorical work for fifty years.

2. Butter is approximately:

  • a) 100% saturated fat
  • b) 63% saturated, 26% monounsaturated
  • c) 30% saturated
  • d) Entirely trans fat
Answer **b.** And the general point matters more than the number: **no food is one type.** Lard has more monounsaturated than saturated fat; olive oil is about 14% saturated.

3. Industrial trans fats are uniquely harmful because they:

  • a) Contain more calories per gram
  • b) Raise LDL and lower HDL simultaneously
  • c) Cannot be digested
  • d) Are radioactive
Answer **b.** No other fat does both. On cardiovascular risk they were substantially worse than the saturated fat they were promoted as replacing.

4. The FDA's 2015 action on partially hydrogenated oils was to:

  • a) Ban them outright immediately
  • b) Determine they were no longer "generally recognized as safe" (GRAS)
  • c) Require a warning label
  • d) Recommend voluntary reduction
Answer **b.** The GRAS determination, with phase-out following. This is the clearest public health success in modern nutrition — and it took decades.

5. The "Keys cherry-picked 7 of 22 countries" claim:

  • a) Is straightforwardly true and well documented
  • b) Confuses the Seven Countries Study with a separate critique using international food-supply statistics
  • c) Was invented recently with no basis
  • d) Was admitted by Keys
Answer **b.** The 22-country figure comes from the Yerushalmy and Hilleboe analysis. Keys's Seven Countries Study was a separately designed prospective cohort with countries chosen for practical and methodological reasons. **There was a legitimate methodological criticism; "cherry-picking" is a garbled version of it.**

6. Replacing saturated fat with refined carbohydrate produces:

  • a) Substantial cardiovascular benefit
  • b) Modest benefit
  • c) No benefit, possibly worse outcomes
  • d) The same benefit as replacing it with polyunsaturated fat
Answer **c.** This is the low-fat era, and it's why meta-analyses of habitual saturated fat intake look null. The comparator does all the work.

7. Which substitution has the best supporting evidence?

  • a) Saturated fat → refined carbohydrate
  • b) Saturated fat → polyunsaturated fat
  • c) Total fat → carbohydrate
  • d) Unsaturated fat → saturated fat
Answer **b.** Consistent across trials and cohorts, and it's the recommendation that survives from the whole diet-heart era: **"replace saturated fat with unsaturated fat"** — not "eat less fat."

8. The 300 mg/day dietary cholesterol limit was dropped from US guidance because:

  • a) Cholesterol turned out to be harmless in all contexts
  • b) The liver adjusts its own production in response to intake, so dietary cholesterol's effect on blood cholesterol is modest for most people
  • c) The egg industry lobbied successfully
  • d) Nobody could measure it
Answer **b.** With three real complications: hyper-responders exist, cholesterol-rich foods often travel with saturated fat, and the picture in type 2 diabetes remains unsettled.

9. Conversion of ALA to DHA in humans is:

  • a) Highly efficient — over 50%
  • b) Poor — commonly estimated under 1–5%
  • c) Impossible
  • d) Better in men than women
Answer **b.** EPA conversion is somewhat better (~5–10%). This is why oily fish, which supplies EPA and DHA directly, is treated as a separate recommendation from ALA-rich plants.

10. The omega-6/omega-3 ratio hypothesis is weakened primarily because:

  • a) Omega-6 fats don't exist in the diet
  • b) Increasing dietary linoleic acid does not reliably increase tissue arachidonic acid, and higher LA intake is generally associated with lower cardiovascular risk
  • c) The ratio has not actually changed historically
  • d) Arachidonic acid is not inflammatory
Answer **b.** The conversion is tightly regulated. Note the honest residual: the omega-3 side of the hypothesis is genuinely supported — most people would benefit from more EPA and DHA — and the *absolute* amount may matter more than the ratio.

11. REDUCE-IT and STRENGTH reached different conclusions about high-dose omega-3. The most discussed explanation is:

  • a) One used a much larger sample
  • b) REDUCE-IT used a mineral oil placebo whose group showed rising LDL and inflammatory markers
  • c) STRENGTH was never completed
  • d) They studied different diseases
Answer **b.** The controversy is genuinely unresolved, and until it is, high-dose omega-3 sits in real uncertainty rather than in a settled verdict.

12. ApoB predicts cardiovascular risk better than LDL-C because it measures:

  • a) The total cholesterol in the blood
  • b) The number of atherogenic particles, each of which carries exactly one ApoB
  • c) The size of the particles only
  • d) HDL function
Answer **b.** It's a numbers game — more particles means more encounters with the artery wall. Two people with identical LDL-C can carry very different particle counts.

13. HDL is described as "a marker, not a lever" because:

  • a) It doesn't exist in the blood
  • b) Drugs that raise HDL have repeatedly failed to reduce cardiovascular events, and Mendelian randomization hasn't supported a simple causal role
  • c) It is impossible to measure
  • d) It only matters in women
Answer **b.** The observational association is robust; the causal interpretation isn't supported. HDL is better read as an indicator of metabolic health than as something to raise.

14. For cooking oil selection, the more important property is:

  • a) Smoke point
  • b) Oxidative stability, which tracks degree of saturation
  • c) Colour
  • d) Price
Answer **b.** Which produces a counterintuitive result: extra-virgin olive oil performs better under household conditions than its modest smoke point suggests, because of its monounsaturated profile and polyphenol antioxidants.

True / False

One-line justification.

15. Saturated fat has been exonerated by recent research.

Answer **False.** It has been **de-escalated**, not exonerated. The null meta-analyses are the unspecified-comparator problem; the LDL mechanism holds; LDL's causal role has if anything strengthened. The honest summary is: real, modest, comparator-dependent, and oversold for thirty years.

16. Coconut oil's MCT content makes it metabolically distinct from other saturated fats.

Answer **False, mostly.** Coconut oil is 80–90% saturated, predominantly **lauric acid** — a 12-carbon fatty acid that behaves much more like a long-chain fat than like the true MCTs (C6–C10) the research concerns. Controlled trials consistently find it raises LDL relative to unsaturated plant oils.

17. PREDIMED was a low-fat trial.

Answer **False, and this is the point.** The Mediterranean arms were **higher** in total fat than the control arm advised to reduce fat. The fat was olive oil and nuts. It's the strongest trial evidence in this chapter, and it points at patterns rather than at a macronutrient.

18. Flax oil is a good choice for frying.

Answer **False.** Highly polyunsaturated, therefore highly susceptible to oxidation. **Dressings only, never heat.** Same for walnut oil.

19. Naturally occurring trans fats in dairy and beef carry the same risks as industrial trans fats.

Answer **False.** They're chemically distinct, consumed in much smaller quantities, and the evidence does not show the same harms. The ✅ verdict in this chapter is specifically about **industrial** trans fats.

Short Answer

20. Explain, in four sentences, how Theo's two contradictory saturated fat headlines can both be accurate.

Answer The meta-analysis compared people who habitually ate **more** saturated fat to people who ate **less**, with whatever they actually ate instead — which across those Western cohorts was substantially refined carbohydrate. The guidance rests on **substitution analyses and trials** where saturated fat was replaced with a *specified* alternative, usually polyunsaturated fat. Replacing saturated fat with PUFA reduces risk; replacing it with refined carbohydrate does not. **Both studies are correct; they are answering different questions, and neither headline stated its comparator.**

21. A patient asks: "Should I stop eating butter?" Give the honest answer in the form the chapter argues for.

Answer **"Compared to what?"** — and then work it through with them. If butter is replaced with **olive oil**, the evidence supports the change: it lowers LDL, and the substitution has the best trial support in the whole diet-heart literature. If it's replaced with **low-fat baked goods or refined snacks**, the change is not supported and may be worse. If they use butter on toast twice a week, the whole question is trivial relative to their alcohol intake, fiber intake, and total energy balance — which is what I told Theo. **And the second half of the answer:** what's their actual risk picture? LDL or ApoB, family history, blood pressure, smoking, diabetes. ⚠️ Butter is a small lever; lipid management is a clinical conversation, and a book about food should be clear about the limits of food.

Scoring

Score Reading
18–21 Strong. You can hold both camps at arm's length, which is the hardest thing this chapter asks.
14–17 Good. Reread §9.5 (substitution) and §9.6.
10–13 Reread §9.4–§9.6 together. The history and the substitution frame have to land as one thing.
Under 10 Reread the chapter. Chapters 10, 19, and 26 all depend on it.

And check yourself on one thing: did you find one of the two 🔬 verdicts in §9.6 easier to accept than the other? Which one, and did that track the evidence or your priors?