Chapter 8 — Key Takeaways
One page. The card to reread before you advise anyone over seventy.
The RDA Is a Floor
0.8 g/kg = the minimum adequate for 97–98% of healthy adults. It answers "how little can I get away with?" and gets read as "how much should I have?"
Derived from nitrogen balance, a method with three limitations that all bias the estimate downward: balance ≠ optimal · short studies allow adaptation to look like adequacy · sweat, skin and hair losses are systematically undercounted.
IAAO methods estimate requirements closer to 1.0–1.2 g/kg.
How Much You Actually Need
| Situation | g/kg/day |
|---|---|
| RDA — minimum adequate | 0.8 |
| Healthy adult, no specific goal | 1.0–1.2 |
| Older adult (65+) | 1.0–1.2, up to 1.5 with illness |
| Resistance training | 1.6–2.2 |
| Endurance athlete | 1.2–1.6 |
| In an energy deficit | 1.6–2.4 — higher, not lower |
| ⚠️ Chronic kidney disease | Restricted, individually prescribed |
⚖️ At very high body weights, calculate from lean or adjusted body weight — total weight inflates the target by 40–50 g.
Quality
Nine essential amino acids. Complete = all nine in useful proportions (animal sources; plus soy, quinoa, buckwheat). Grains limit on lysine, legumes on methionine — which is why they complement, and why combining-at-a-meal is unnecessary.
DIAAS > PDCAAS (ileal digestibility, uncapped). It widens the animal–plant gap, which is an honest point.
Leucine is the mTOR trigger. Threshold ≈ 2.5–3 g per dose — about 25 g whey, 30–35 g most animal proteins, more from plants.
Dose, Distribution, and the Window
The plateau: MPS response maximizes around 20–40 g per meal in young adults (~0.24–0.40 g/kg). Higher in older adults, with larger training volumes, and with lower-quality protein.
That's synthesis, not absorption. You absorb essentially all of it; the surplus goes to enzymes, immune proteins, gut lining turnover, connective tissue, or is oxidized.
The window is hours — plausibly 24+ — not thirty minutes. Total daily intake dominates. Early studies were confounded by fasted training.
Default: three to four servings of 25–40 g. Breakfast is where nearly everyone falls short — a typical Western breakfast is under 10 g.
Older Adults — the headline
Anabolic resistance: the same dose produces a blunted response. Older adults may need 35–40 g per meal with adequate leucine.
Requirements up, intake down, simultaneously: appetite declines (anorexia of ageing) · taste and smell dull · chewing gets harder (and meat is the hardest food to chew and the highest-protein one) · cooking for one is miserable · medications reduce appetite · fixed incomes · and the belief that "at my age you don't need much."
Sarcopenia determines whether you can stand from a chair, climb stairs, catch a stumble, and recover from hospital. Protein plus resistance training is the intervention; each alone substantially underperforms.
Kidneys and Bones — both fears fail
| Fear | Reality |
|---|---|
| Kidneys | Raised filtration in healthy kidneys is normal adaptation, not damage. No demonstrated harm in people with normal function. ⚠️ In existing CKD, restriction is genuine evidence-based management — set by a nephrologist. |
| Bones | Acid-ash hypothesis overturned. The extra urinary calcium is substantially explained by increased intestinal absorption. Higher protein is associated with better bone density and lower fracture risk. |
And note the cost of the bone error: older adults told to limit protein for their bones were exactly the people who most needed more of it for their muscles.
Cost per 20 g of Protein
| Dried lentils | $0.25 |
| Milk | $0.50 |
| Eggs | $0.60 |
| Canned tuna | $0.88 |
| Whey powder | $0.92 — mid-table, a legitimate convenience tool |
| Chicken breast | $1.10 |
| Greek yogurt | $1.22 |
| "High protein" cereal | $2.10 |
| Protein bar | $2.90 |
| "Protein water" | $3.60 |
Ten-fold spread. No label prints this number, and it takes ten seconds to calculate.
Common Mistakes (and the fix)
| Mistake | Fix |
|---|---|
| Treating the RDA as a target | It's a floor with a known downward bias |
| "Older people need less protein" | They need more — anabolic resistance |
| Combining rice and beans at each meal | The amino acid pool does it across the day |
| "Only 30 g per meal is absorbed" | That's the synthesis plateau, not absorption |
| Sprinting to the shake within 30 minutes | The window is hours; the daily total dominates |
| Avoiding protein for kidney or bone health | Neither fear survives in healthy people |
| Buying bars to hit a target | Fix breakfast first — it's cheaper and it's where the gap is |
| Advising food without resistance training in an older adult | That's half the intervention, and the half that doesn't work alone |
Verdict Summary
| Claim | Verdict | Why |
|---|---|---|
| Plant proteins are incomplete — combine at each meal | ❌ Not supported | Amino acid pool; retracted by Lappé in 1981. Residual: plant eaters aim 10–20% higher on total |
| Protein within 30 minutes of training | 🟠 Probably false | Window is hours; daily total dominates; early studies confounded by fasted training |
| High protein damages kidneys | ❌ Not supported in healthy people | ⚠️ ✅ Genuine clinical variable in existing CKD — two different claims |
| High protein leaches calcium from bones | ❌ Not supported | Mechanism overturned; outcome evidence points the other way |
| You need a supplement to hit your target | 🟡 Unclear / it depends | Works, isn't superior to food, useful for some. Fix breakfast before you buy a tub. |
⚠️ When to See a Professional
Unintentional weight loss in an older adult is a red flag, not a success. So are: difficulty rising from a chair · a fall · substantially slowed walking speed · any hospital admission (bed rest costs muscle that takes months to rebuild).
Chronic kidney disease, a single kidney, or a transplant: protein intake is a clinical variable set by a nephrologist and renal dietitian. Do not apply the healthy-population verdict to yourself.
If you have an older parent: the question isn't "are you eating?" It's "how much protein, at how many meals?"
What We Still Don't Know
The longevity-optimal protein intake. Higher protein is well supported for lean mass, satiety, and older-adult function. Its lifespan effects are contested — some animal and observational work associates lower protein and lower mTOR signalling with longer life, while human data is inconsistent. The optimum may genuinely differ by age, lower in midlife and higher later, and the evidence can't currently settle it.
Anyone who tells you they know is extrapolating from mice.
One Thing to Remember
Ruth said: "I'm not doing anything. Why would I need it?"
It is exactly backwards. The less you do and the older you are, the more protein it takes to hold on to what you have — and the intervention that changes it costs about £4 a week and is almost never prescribed.