Chapter 19 — Self-Check Quiz

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

Questions

1. The "seed oils" category is defined primarily by:

• a) Linoleic acid content above a set threshold
• b) Provenance — seed origin, industrial extraction, refining
• c) Smoke point
• d) Omega-6 to omega-3 ratio

2. Approximate linoleic acid content, highest to lowest:

• a) Canola > safflower > olive
• b) Safflower > soybean > canola > olive
• c) Olive > canola > soybean
• d) All seed oils are approximately equal

3. Which is usually not on the "hateful eight" list despite having roughly three times canola's linoleic acid?

• a) Coconut oil
• b) Peanut oil
• c) Butter
• d) Palm oil

4. The strongest factual point on the sceptical side is:

• a) Seed oils were unknown before 1900
• b) Human adipose tissue linoleic acid content rose substantially over the past half-century
• c) Seed oils cause measurable inflammation in trials
• d) Hexane residues exceed safety limits

5. Adipose tissue measurement is valuable as an exposure assessment because:

• a) It is cheaper than food surveys
• b) It doesn't depend on anyone remembering what they ate
• c) It measures disease directly
• d) It can be done retrospectively on any patient

6. The enzyme competition at the heart of the ratio argument involves:

• a) Lipoprotein lipase
• b) Delta-6 desaturase, shared by the omega-6 and omega-3 pathways
• c) HMG-CoA reductase
• d) Pancreatic lipase

7. When tested directly, increasing dietary linoleic acid:

• a) Reliably raised CRP and IL-6
• b) Generally did not raise circulating inflammatory markers
• c) Raised inflammatory markers only in men
• d) Has never been tested

8. The more decisive failure of the mechanism is that raising LA intake:

• a) Lowers adipose LA
• b) Does not proportionally raise tissue arachidonic acid — the conversion is regulated and saturable
• c) Raises EPA and DHA
• d) Has no effect on adipose composition

9. Essential fatty acid deficiency presents with:

• a) Anaemia and glossitis
• b) Scaly dermatitis, impaired wound healing, growth failure in infants
• c) Night blindness
• d) Peripheral neuropathy

10. The existence of EFA deficiency matters to this debate because:

• a) It proves seed oils are healthy
• b) It means the coherent sceptical argument must be about dose, not toxicity
• c) It disproves the ratio hypothesis
• d) It is only relevant to infants

11. Person A cuts omega-6 by 60%; Person B eats oily fish twice weekly. Both reach a 6:1 ratio. The key difference is:

• a) Person A's EPA/DHA status is largely unchanged; Person B's is substantially raised
• b) Person B's ratio is misleading
• c) There is no meaningful difference
• d) Person A has better outcomes

12. ALA-to-EPA/DHA conversion in humans is:

• a) Highly efficient
• b) Poor — a small percentage, lower still for DHA, and lower in men
• c) Impossible
• d) Dependent on vitamin C

13. The Sydney Diet Heart and Minnesota Coronary Experiment reanalyses found that replacing saturated fat with linoleic acid:

• a) Raised cholesterol and increased mortality
• b) Lowered cholesterol but did not reduce mortality
• c) Had no effect on cholesterol
• d) Reduced mortality substantially

14. The strongest counter-argument to those trials is that:

• a) They were too small to analyze
• b) The intervention oils included margarine high in industrial trans fat
• c) They were never peer reviewed
• d) The data were fabricated

15. The alarming oxidation research applies principally to:

• a) Sealed bottles in a cupboard
• b) Oil heated once at home and discarded
• c) Repeatedly heated commercial fryer oil
• d) Cold-pressed oils

16. Which has the lowest smoke point?

• a) Refined canola
• b) Ghee
• c) Butter
• d) Refined avocado

17. Refining a seed oil:

• a) Lowers its smoke point
• b) Raises its smoke point, removes antioxidants, and can generate small amounts of trans fat
• c) Has no effect on smoke point
• d) Adds antioxidants

18. Residual hexane in finished refined oil is:

• a) Above regulatory limits
• b) In the parts-per-million range, far below established limits
• c) Undetectable by any method
• d) The main safety concern with seed oils

19. §19.11's confounding problem means:

• a) Seed oils are proven safe
• b) Seed oil intake and ultra-processed food intake are not separable exposures, preventing both indictment and exoneration
• c) Only randomized trials can be trusted
• d) Cohort studies have been discontinued

20. Why do people who eliminate seed oils often genuinely feel better?

• a) The omega-6 ratio normalizes within days
• b) Removing seed oils removes fried takeaway, packaged snacks and most ultra-processed food — a bundled intervention
• c) Placebo effect only
• d) Tallow contains compounds that reduce inflammation

Answers

1. b) Provenance. ⚠️ Chapter 18 Case Study 1's exact failure: a provenance category answering a compositional question. Canola (~19% LA) is closer to olive oil (~10%) than to safflower (~70%), and it's on the list; peanut (~32%) usually isn't. §19.1.

2. b) Safflower > soybean > canola > olive. Roughly 70% > 51% > 19% > 10%. ⚠️ A sevenfold spread inside a category treated as homogeneous. §19.1.

3. b) Peanut oil. ~32% linoleic acid. Its absence from the list is the clearest demonstration that the category tracks origin rather than composition. §19.1.

4. b) Adipose tissue LA rose substantially. ⚠️ Take this seriously — it's a documented tissue-level change in human body composition across decades, and it's routinely omitted by people arguing the mainstream position. "Unprecedented" is not "harmful," but it is an excellent reason to investigate. §19.3.

5. b) It doesn't depend on recall. ⚠️ Chapter 2 §2.5's biggest problem in nutrition epidemiology — self-reported intake — is bypassed entirely. This makes it one of the better exposure measurements in the whole field. §19.3.

6. b) Delta-6 desaturase. Both the omega-6 and omega-3 pathways use it, so more LA means less ALA converted. This competitive step is what makes the ratio argument mechanistically coherent — and it is a real biochemical relationship. §19.4.

7. b) Generally did not raise inflammatory markers. Across systematic reviews of controlled trials. ⚠️ The trials are modest and the markers are proxies — real limitations — but the prediction was clear, it was tested repeatedly, and it wasn't confirmed. §19.5.

8. b) It does not proportionally raise tissue AA. ⚠️ This is the broken link, and it's the load-bearing one. Adipose LA rises with intake (§19.3 measured it); membrane AA largely doesn't follow, because the conversion is regulated and saturable. A pathway existing is not the same as a pathway being rate-limiting — Chapter 13's antioxidants, exactly. §19.5.

9. b) Scaly dermatitis, impaired wound healing, growth failure. Documented in patients on fat-free parenteral nutrition and in infants on inadequate formulas; it resolves when LA is provided, which is what makes it a deficiency. §19.4.

10. b) The coherent sceptical argument must be about dose. ⚠️ A framework calling LA a toxin has to explain a named deficiency syndrome caused by its absence. The defensible version argues requirement is 1–2% of energy and intake is 5–8% — that's an argument about excess, and it's the one §19.12 asks to see specified. §19.4.

11. a) Person A's EPA/DHA status is largely unchanged. ⚠️ Same ratio, two routes, completely different physiological meaning — and the number on the page is identical. Because ALA conversion is poor, cutting omega-6 doesn't reliably put EPA and DHA in tissue. Eating fish does. §19.5.

12. b) Poor. A small percentage, worse for DHA, lower in men than women. ⚠️ This is why preformed EPA/DHA from oily fish (🟢) is the best-evidenced action in the chapter — it bypasses the bottleneck entirely. §19.5.

13. b) Lowered cholesterol but did not reduce mortality. Recovered data, reanalyzed and published in the BMJ (Sydney 2013, Minnesota 2016, Ramsden et al.). ⚠️ This is real and uncomfortable for the mainstream position, and anyone presenting this debate without it is not giving you the argument. §19.6.

14. b) The oils included trans-rich margarine. ⚠️ A trial of trans-fat-containing margarine is not a trial of canola oil — and Chapter 9 established trans fat as genuinely harmful. Plus high dropout, institutionalized populations, short exposure. They're also a real publication-bias scandal — Chapter 2 §2.8's file drawer, vindicated, which is a point that applies to all the literature including the parts sceptics like. §19.6.

15. c) Repeatedly heated commercial fryer oil. ⚠️ This is the studied condition, and it isn't your cupboard. The chemistry is certain enough that jurisdictions regulate fryer oil on total polar compounds. "Seed oils oxidize and produce toxic aldehydes" is true; "therefore the bottle in your kitchen is delivering them" doesn't follow from those studies. §19.8.

16. c) Butter, at roughly 150°C — well below refined canola (~220–230°C), ghee (~250°C) and refined avocado (~260°C). ⚠️ The popular claim that refined seed oils are "unstable and shouldn't be heated" is backwards on this specific measure. §19.9.

17. b) Raises smoke point, removes antioxidants, can generate small trans. ⚠️ All three, which is why §19.10 gives three separate verdicts. Refining removes the free fatty acids and particulates that smoke — so the process the argument objects to is the one that raises the smoke point — while also stripping polyphenols and, at the deodorizing step, generating small trans amounts. §19.9, §19.10.

18. b) Parts-per-million, far below limits. ❌ Not a meaningful risk in the finished product. (The occupational and environmental case for hexane is separate and more legitimate — and it isn't about your cooking oil.) §19.10.

19. b) Not separable exposures. ⚠️ And the confounding is symmetric — it prevents the cohorts from indicting seed oils and from exonerating them, because "diet quality" adjustments are partly measuring seed oil intake. This is why the epidemiology cannot settle this debate and probably never will. §19.11.

20. b) A bundled intervention. ⚠️ You cannot remove seed oils without removing fried takeaway, packaged snacks, most restaurant food and most UPF — six changes, one credited (Chapter 17 §17.1, shape 8). This is not a debunk: the intervention works and the explanation is wrong, which is the most common pattern in this book. Chapter 22 has the actual mechanism. §19.11.

Scoring

Three items worth checking regardless of score.

Question 8. ⚠️ The broken link is the chapter's decisive finding. If you missed it, you'll keep reading the mechanism as though it were evidence.

Question 15. ⚠️ If you missed the form question, you'll act on the wrong thing — changing your cupboard instead of your takeaway.

Question 20. ⚠️ This is the one that generalizes furthest, and Chapter 22 depends on you having it.