Chapter 14 — Exercises

C1 — the ferritin question — is the highest-yield exercise in Part III, and possibly in the book. If you tick two boxes, do it this week.

Difficulty legend: ⭐ basic recall · ⭐⭐ applied · ⭐⭐⭐ synthesis and judgment · ⭐⭐⭐⭐ extension

Selected answers in Appendix J.

Part A — Conceptual Understanding ⭐

A1. Give four ways minerals behave differently from vitamins, and one consequence of each.

A2. Compare heme and non-heme iron: sources, absorption range, and susceptibility to modification.

A3. List four enhancers and four inhibitors of non-heme iron absorption.

A4. What is hepcidin and what does it do? What happens to it during inflammation?

A5. Explain the difference between ferritin and hemoglobin, and describe the order in which iron depletion proceeds.

A6. Why is a normal ferritin not always reassuring? What would you measure alongside it?

A7. List six groups at elevated risk of iron deficiency.

A8. Why is blood calcium useless as a measure of calcium nutrition?

A9. Why is serum magnesium a poor marker of magnesium status?

A10. What is the UL for zinc, and what does exceeding it chronically cause?

A11. Why are Brazil nuts a genuine caution rather than a health food?

A12. Name four reasons iodine intake has been falling in some wealthy countries.

A13. State what is and isn't disputed about sodium.

Part B — Applied Analysis ⭐⭐

B1. Devi's ferritin is 11 with a hemoglobin of 12.6. Explain to a non-specialist, in four sentences, why she is iron-deficient despite a "normal" blood test.

B2. List every factor contributing to Devi's iron deficiency. Aim for six, and identify which one is an energy problem rather than an iron problem.

B3. Design an iron-repletion plan for a vegetarian athlete. Include: supplement timing relative to tea/coffee and calcium, what to take it with, dietary changes, and what you'd monitor and when.

B4. A 58-year-old man is found to have iron deficiency anemia. His GP prescribes iron. What has been missed, and why does it matter?

B5. Explain why calcium supplements improve bone density slightly but don't reliably reduce fractures. Name the Chapter 2 concept involved.

B6. Walt takes 50 mg of zinc daily in an "immune blend." Calculate how far above the UL that is, explain the mechanism of harm, and describe what you'd monitor.

B7. A pregnant woman uses Himalayan pink salt, avoids dairy, and drinks oat milk. Which mineral is the concern, why, and what would you check?

B8. Two people argue about sodium: one cites DASH-Sodium, one cites PURE. Explain what each study showed, why they appear to conflict, and where the methodological dispute actually sits.

Part C — Skills & Practice ⭐⭐–⭐⭐⭐

C1. Answer the ferritin question. The Project Checkpoint's Step 1. Tick the boxes honestly. Two or more → ask for ferritin with CRP, using the exact sentence: "Could I have my ferritin checked as well as my full blood count?"

C2. Fix your absorption for free. Audit when you drink tea and coffee relative to meals, and when you take any calcium or iron supplement. Move tea and coffee to between meals. This costs nothing and the effect is substantial.

C3. Check your salt. Is it iodized? Check the label, not your memory. If you're pregnant or planning, check whether your prenatal contains iodine — not all do.

C4. Add up your minerals against the UL. Every supplement, multivitamin, and fortified product. Particularly zinc (UL ~40 mg) and selenium (UL ~400 µg). Anything over?

C5. Estimate your potassium. Using Appendix A, estimate a day's potassium intake. Compare to 2,600–3,400 mg. Most people are well below — where are you, and what one food would move it most?

C6. Find your sodium. Not the shaker — the packages. Add up sodium from packaged and restaurant food over two days. Compare to your total. What proportion came from the shaker?

C7. Ask someone. If you know a woman who runs, cycles, or trains seriously, ask whether her ferritin has ever been checked. The answer is usually no. (Readers of drafts have found two confirmed deficiencies doing this.)

Part D — Synthesis & Critical Thinking ⭐⭐⭐

D1. The chapter refuses to resolve the sodium question. Is that appropriate humility or an abdication? A reader has to eat tonight. What should a book do when the evidence is genuinely contested?

D2. Ferritin is cheap, the indications are clear, and it's routinely not measured. Design a system change that would fix this. What would it cost, and what would it displace?

D3. Iodized salt is a public health triumph being quietly undone by consumer preference for specialty salts and plant milks. Whose problem is this to solve, and how? Consider mandatory fortification of plant milks.

D4. The chapter says iron deficiency is "a finding, not a diagnosis." Apply that principle to three other findings in this book. Where else does treating the number risk missing the cause?

D5. Calcium supplementation has weak fracture evidence, and protein plus resistance training has better evidence. Yet calcium is recommended far more often. Why? What does that reveal about how recommendations are selected?

Part M — Mixed & Interleaved Practice ⭐⭐–⭐⭐⭐

M1. (With Chapter 13.) State the threshold concept, then give the vitamin version (Walt) and the mineral version (Devi) side by side. What's structurally identical about them?

M2. (With Chapter 4.) Devi's energy availability is 31.8 kcal/kg FFM. Explain why her iron problem is partly an energy problem, and why supplementing iron without fixing energy would be incomplete.

M3. (With Chapter 6.) Name three mechanisms by which low iron impairs endurance performance, using the metabolic pathways from Chapter 6.

M4. (With Chapter 12.) The sodium J-curve and the alcohol J-curve share a structural problem. Name it, and say what evidence would resolve each.

M5. (With Chapter 8.) For fracture risk in an older adult, rank these by strength of evidence: calcium supplements · vitamin D · protein intake · resistance training. Justify.

M6. (With Chapters 7 and 11.) Phytate inhibits iron, zinc and calcium absorption. Chapter 7 gave whole grains ✅ despite this. Reconcile.

M7. (With Chapter 5.) Walt's "immune blend" contained 50 mg zinc and 3,000 µg biotin. Using Chapter 14 and Chapter 13, describe both harms — one nutritional, one diagnostic.

M8. (Revisit at Chapter 23.) Predict how Chapter 23 will handle iron in athletes. What specifically will it add beyond this chapter?

Part E — Research & Extension ⭐⭐⭐⭐

E1. Read the literature on iron deficiency without anemia — particularly trials of iron repletion for fatigue in non-anemic women and for performance in athletes. How consistent are the findings? What ferritin threshold do the trials use, and does it vary?

E2. Investigate hepcidin and exercise. How long after hard training is absorption suppressed, and what does that imply for supplement timing in athletes? This is genuinely practical and rarely taught.

E3. Read the DASH-Sodium trial and the PURE sodium analyses, plus at least two commentaries on the spot urine versus 24-hour urine measurement dispute. Write a page on what would settle it.

E4. Investigate the re-emergence of iodine insufficiency in a wealthy country — the UK, US, Australia and several European countries all have relevant literature. What's driving it, who is affected, and what policy responses have been proposed?

E5. Read about hereditary hemochromatosis — prevalence, genetics, presentation, and why iron supplementation without testing is dangerous. Then consider whether population screening would be justified.

E6. Look into the soil depletion claim properly. Find the historical food composition comparisons, then find the methodological critiques. Where does the evidence actually land, and why do selenium and iodine behave differently from iron and zinc?