Chapter 8 — Further Reading

Real sources only. Where I'm unsure of exact details, I describe the source rather than inventing a citation.

The reference documents

Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Institute of Medicine / National Academies, 2005). Free through the National Academies Press.

The protein chapter is where 0.8 g/kg comes from, and reading the committee's own account of the nitrogen balance data — including its stated uncertainties — is the most efficient way to understand why §8.2 calls it a floor. The document is considerably more hedged than the number's public life suggests. For: students, clinicians, and anyone who quotes the RDA.

On IAAO: search PubMed for "indicator amino acid oxidation protein requirement" and read a review. The methodological argument between IAAO and nitrogen balance is genuinely interesting, and it's a good example of a field disagreeing about a measurement rather than about a conclusion. For: students and dietitians.

On protein in older adults — the most important section here

The PROT-AGE Study Group recommendations on dietary protein for older people, published in JAMDA (2013), and the ESPEN (European Society for Clinical Nutrition and Metabolism) guidance on protein in older adults.

These are where the 1.0–1.2 g/kg (rising to 1.2–1.5 with illness) figures come from. Both are freely findable, both are written for practitioners, and both are considerably more assertive than the RDA.

The gap between these recommendations and what older adults are actually told is the single largest unexploited opportunity in clinical nutrition, and reading them makes that gap uncomfortably visible. For: anyone with an older parent, and every clinician.

On sarcopenia: search for the EWGSOP2 (European Working Group on Sarcopenia in Older People) consensus definition, and for reviews on resistance training plus protein supplementation in older adults. The training half is at least as important as the food half — Chapter 8's Case Study 1 is why. For: everyone. If a section of this book saves someone's independence, it's this one.

On protein quality and the combining myth

Frances Moore Lappé, Diet for a Small Planet (Ballantine, 1971; revised 1981 and subsequently).

Read the 1981 or later edition's discussion of protein combining, where Lappé withdraws the requirement she popularized. It's a short passage and it's a genuinely admirable piece of public self-correction — and the fact that the original claim outlived the retraction by forty years is a case study in how corrections fail to propagate (Chapter 1 §1.4). For: everyone who was taught to combine rice and beans.

Position of the Academy of Nutrition and Dietetics on vegetarian diets (eatright.org). The professional consensus position, which addresses protein adequacy directly and is unambiguous about combining. For: plant-based eaters and anyone advising them.

On DIAAS versus PDCAAS: the FAO reports on protein quality evaluation are the primary source for the DIAAS methodology. Worth reading for why the PDCAAS cap exists and what removing it changes. For: students, and anyone arguing about plant versus animal protein quality.

On dose, timing, and the anabolic window

Alan Aragon and Brad Schoenfeld's work on nutrient timing — particularly their review examining the post-exercise "anabolic window," published in the Journal of the International Society of Sports Nutrition. This is the paper that most directly addresses §8.6, and its conclusion — that total daily protein dominates and the window is far wider than claimed — has held up well. For: anyone who has ever sprinted to a changing-room shaker.

The ISSN position stand on protein and exercise (jissn.biomedcentral.com, open access). Covers dose, timing, distribution, and quality for active individuals, with the 1.4–2.0 g/kg range for trained populations. Freely available and unusually readable for a position stand. For: coaches, trainers, and athletes.

On muscle protein synthesis dose-response: search for work by Stuart Phillips, Luc van Loon, and colleagues. These groups have produced most of the dose-response and distribution data, including the older-adult anabolic resistance findings. Phillips in particular writes accessibly about where the evidence is strong and where it's been oversold. For: students and coaches wanting the primary literature.

On the kidney and bone questions

On kidneys: search for reviews on "high protein diet renal function healthy adults." The consistent finding of no demonstrated harm in people with normal function — alongside the genuine importance of restriction in existing CKD — is well documented.

For the clinical side: KDIGO (Kidney Disease: Improving Global Outcomes) guidelines (kdigo.org) on nutrition in CKD. This is the authoritative source, and it makes clear how different the recommendation becomes once kidney function is impaired. ⚠️ If you have kidney disease, this is the literature that applies to you, not the healthy-population studies.

On bones: search for systematic reviews on dietary protein and bone health, and for position statements from bone-health organizations. The reversal of the acid-ash hypothesis is well documented and is one of the clearer examples in nutrition of a plausible mechanism losing to outcome data. For: anyone who was advised to limit protein for bone health, and anyone still advising it.

On protein and longevity — the genuinely open question

There is a real research disagreement here, and both sides are worth reading.

The case for lower protein: search for work on caloric restriction, mTOR, and lifespan in model organisms, and for observational analyses associating protein intake with mortality that differ by age. Valter Longo's research and popular writing represent the strongest version of this position — read it noting that he has commercial interests in this space, which is a reason to read carefully rather than to dismiss (Chapter 1 §1.5).

The case for higher protein: the sarcopenia and older-adult literature above, plus the lean-mass and function evidence.

Reading both is the exercise. Notice that the two bodies of evidence apply most strongly to different life stages, and that the honest conclusion in §8.13 — that the optimum may differ by age and the evidence can't currently settle it — is one that neither camp finds satisfying. For: anyone who has encountered a confident claim about protein and longevity.

Practical references

USDA FoodData Central — fdc.nal.usda.gov. The source for every figure in §8.12's table. Look up anything.

On supplement quality: third-party certification programmes — NSF Certified for Sport, Informed Sport, and USP — verify that a product contains what it claims and is free of banned substances. Chapter 16 explains why this matters more than it should have to under DSHEA 1994. For: anyone buying protein powder, and essential for competitive athletes.

A note on what to be careful with

The protein literature has an unusual problem: it's mostly correct and mostly oversold by the same people.

Fitness content citing Phillips, van Loon, Aragon and Schoenfeld is usually citing them accurately — and then attaching a product. The science of protein dose and distribution is genuinely good, and the gap between "1.6 g/kg supports muscle gain" and "buy this bar" is where the money sits.

The tell: does the source ever say "you probably already eat enough"? Most people reading fitness content are at 1.2–1.6 g/kg already. A source that never once tells a reader they're fine is selling something — and the population with the genuine deficit isn't reading fitness content at all.

She's seventy-nine and she's had toast for breakfast for forty years.