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Chapter 13 — Further Reading
The single best resource
NIH Office of Dietary Supplements fact sheets — ods.od.nih.gov
Free, regularly updated, available in both consumer and professional versions, and there is one for every vitamin in this chapter. They state plainly where evidence is weak, list drug interactions and upper limits, and name the populations genuinely at risk.
If you read one thing from this page, make it the B12 fact sheet and the vitamin D fact sheet. They are better than any table I could print and they'll be current after this book isn't. For: everyone. Genuinely the highest-value free nutrition resource in existence.
The reference framework
Dietary Reference Intakes (National Academies) — free through the National Academies Press. The source for EAR, RDA, AI and UL, and for the reasoning behind each value.
Worth reading the introductory chapter on how the DRIs are derived even if you never look up a number. It's where §13.2's point about the RDA being set to cover 97–98% comes from, and understanding that single fact defuses most supplement marketing. For: students, clinicians, and anyone who has ever been told "most people don't get enough."
FDA guidance on the Daily Value and supplement labelling (fda.gov) — explains why labels show
%DV rather than %RDA, and how the DV figures were set. Relevant to Exercise C4.
On folic acid — the success story
The MRC Vitamin Study Research Group, "Prevention of neural tube defects: results of the Medical Research Council Vitamin Study," The Lancet, 1991. The trial that settled it. Short, readable, and genuinely one of the most consequential nutrition papers ever published.
Czeizel and Dudás (NEJM, early 1990s) for the primary-prevention trial in Hungary.
On fortification outcomes: search for national analyses of neural tube defect prevalence before and
after mandatory folic acid fortification — the CDC (cdc.gov) publishes US data, and Canadian,
Chilean and other national analyses are findable. Reading actual prevalence curves is more persuasive
than any summary.
For: everyone. This is what a nutrition victory looks like, and almost nobody has seen it.
On B12 and metformin
American Diabetes Association Standards of Care in Diabetes (diabetesjournals.org, published
annually and freely available). Search within it for the B12 recommendation in metformin-treated
patients. This is the guidance that Chapter 13's opening case violates, and it is not obscure.
For: anyone taking metformin, and every clinician who prescribes it.
On B12 more broadly: the NIH ODS B12 fact sheet, and reviews on B12 deficiency diagnosis — particularly the role of methylmalonic acid when serum B12 is borderline, which is the test that resolves the ambiguous results.
On PPIs and B12: search for "proton pump inhibitor vitamin B12 deficiency" reviews. The association is well documented and rarely acted on.
On vitamin D — read both sides of the threshold dispute
The National Academies (IOM) 2011 report on calcium and vitamin D — the basis for the ~20 ng/mL adequacy framing, and explicit about what the committee concluded and why.
The Endocrine Society clinical practice guideline on vitamin D — the basis for the higher sufficiency threshold.
Read both. The disagreement is genuine, partly definitional, and it determines whether "most people are deficient" is true. Very few readers have looked at the actual reasoning on either side. For: anyone who has been told their vitamin D is low.
The VITAL trial (NEJM, 2018) and its subsequent analyses — vitamin D and omega-3 for cardiovascular disease and cancer. Read the main paper and at least one commentary arguing it was misinterpreted.
On the isolated-nutrient failures
ATBC and CARET — see Chapter 2's further reading. The National Cancer Institute
(cancer.gov) has accessible summaries.
SELECT (Selenium and Vitamin E Cancer Prevention Trial) — published in JAMA. Read what was expected and what was found.
On homocysteine-lowering trials: search for "homocysteine lowering cardiovascular outcomes trials". The pattern — marker moved exactly as designed, events unchanged — is the cleanest surrogate-endpoint failure available and it's worth seeing in the primary literature.
Cochrane reviews on antioxidant supplementation and mortality — freely available in plain-language summary. Note the direction of the findings and the certainty ratings.
On vitamin C
Cochrane: "Vitamin C for preventing and treating the common cold." Free plain-language summary. Read it, including the subgroup finding in people under extreme physical stress — that exception is real, is rarely mentioned, and is a good example of a genuine signal buried inside a null result.
On Linus Pauling: his advocacy is a case study in how far a Nobel laureate's confidence can travel without evidence. Worth reading about as an epistemics lesson rather than a chemistry one.
On toxicity and interactions
NIH ODS fact sheets again — each includes a UL section and a drug interactions section.
On biotin interference: the FDA safety communications on biotin and laboratory test interference (2017, updated subsequently). Short, specific, and directly relevant to Chapter 16. ⚠️ If you take a "hair, skin and nails" supplement, read this one before your next blood test.
On vitamin K and warfarin: guidance from anticoagulation services — the message is consistency, not avoidance, and the patient-facing materials are generally good.
A note on what to be careful with
The vitamin literature has an unusual asymmetry compared with the rest of this book: the deficiency science is among the strongest and least contested material in all of nutrition, and it sits directly alongside a marketing category built on extending it far beyond where it holds.
The failure mode is to reject both together. A reader who correctly concludes that most supplement claims are unsupported, and therefore stops taking B12 while eating a vegan diet, has made a much worse error than the one they were trying to avoid.
The test that separates them: does the claim identify who is deficient, why, and how it would be measured? Folic acid before conception specifies the population, the mechanism, the timing, and the dose. "Supports immune health" specifies nothing — and the difference between those two sentences is the whole of Part III.