Where 0.8 g/kg Came From
The '0.8 g/kg/day' RDA is shared by the US, EU, and Korea's KDRI 2020. But knowing where the number came from changes how you read it. RDAs trace to 1940s nitrogen balance studies — measuring the intake at which nitrogen in equals nitrogen out, with a safety margin. In short, it is the 'minimum to avoid deficiency,' not 'optimum for health.'
McMaster's Stuart Phillips has argued for years that this figure is 'systematically low' for active adults, elders, and lifters. Nitrogen balance does not measure functional outcomes like muscle protein synthesis (MPS), signaling, immunity, or bone health — only whether nitrogen leaks.
Morton 2018 BJSM — 1.6 g/kg Is the Hypertrophy Ceiling
Morton, Murphy, Schoenfeld, Phillips et al. 2018 in British Journal of Sports Medicine was a watershed meta-analysis: 49 RCTs, n=1,863 of resistance-trained adults. Findings:
- Added protein significantly increased lean mass — but no further benefit beyond 1.6 g/kg/day (95% CI 1.03–2.20)
- Effect largest in young adults; blunted with age ('anabolic resistance')
- Total daily protein matters more than source or timing
For a 70 kg adult, 1.6 g/kg is ~112 g — twice the RDA's 56 g. Caveat: only in those actually lifting. Protein without training does not grow muscle.
Elders Need More — PROT-AGE 2013
Bauer et al. 2013 in Journal of the American Medical Directors Association — the PROT-AGE international consensus — recommends 1.0–1.2 g/kg/day for adults 65+, rising to 1.2–1.5 g/kg with acute illness, chronic disease, or active lifestyles.
The reason is anabolic resistance: elder muscle responds more weakly to the same protein dose. A stronger stimulus (more protein, more leucine) is required. Sticking to the RDA accelerates the slide into sarcopenia.
Per-Meal Protein — The Leucine Threshold and the 20–40 g Rule
Total isn't everything; distribution matters.
Witard et al. 2014 in American Journal of Clinical Nutrition found ~2.5–3 g of leucine per meal triggers maximal MPS. Leucine is the molecular switch for mTORC1. Below threshold, MPS doesn't fire.
Practically, that's 20–40 g of high-quality protein per meal — 100 g chicken, four eggs, one block of tofu, or 200 g Greek yogurt plus nuts. Macnaughton 2016 in Physiological Reports showed 40 g out-stimulated 20 g after whole-body resistance training, challenging older 'plateau at 20 g' thinking.
Four evenly-spaced meals (20–40 g each) accumulate more 24-hour MPS than one large bolus (Areta 2013). Korean eating patterns concentrate protein at lunch and dinner with sparse breakfasts — fixing breakfast alone yields large gains.
Targets by Population
| Population | g/kg/day | Evidence | Sample plan (60 kg) |
|---|---|---|---|
| Average sedentary adult | 0.8–1.0 | RDA, KDRI 2020 | 48–60 g — 2 eggs + half tofu + 100 g chicken |
| Active adult / dieting | 1.2–1.6 | Morton 2018 BJSM | 72–96 g — above + yogurt, fish |
| Resistance trainee | 1.6–2.2 | Morton 2018, Helms 2014 | 96–132 g — 4 meals × 25–33 g |
| Healthy adults 65+ | 1.0–1.2 | Bauer 2013 PROT-AGE | 60–72 g — dairy, eggs, fish, legumes each meal |
| 65+ chronic illness / rehab | 1.2–1.5 | PROT-AGE | 72–90 g — with clinician guidance |
| Elite endurance / competitive athletes | 1.6–2.0 | Jäger 2017 ISSN | 96–120 g — adjust for training load |
Animal vs Plant — The DIAAS Era
Quality matters as much as quantity. In 2013 FAO replaced PDCAAS with DIAAS (Digestible Indispensable Amino Acid Score), measured at the terminal ileum for accuracy.
- Dairy, egg, beef: DIAAS ≥ 1.0 (complete)
- Soy isolate, pea isolate: 0.7–0.9
- Wheat or rice alone: 0.4–0.6 (require complementation)
Van Vliet et al. 2015 in J Nutr found whey out-stimulated soy for MPS at equal protein doses in young adults. But Pinckaers et al. 2024 follow-up shows that higher doses or smart blends (soy + pea + rice) match animal protein. The lesson isn't 'plant is inferior'; it's 'compensate with quantity and variety.'
Korean food culture is rich in plant protein — soy, tofu, cheonggukjang, soybean sprouts. One block of tofu (~300 g) contains 24–30 g protein, on par with a chicken breast.
Pre-Sleep Protein — Snijders 2015
Snijders et al. 2015 in Journal of Nutrition found that 40 g of casein 30 min before bed significantly raised overnight MPS, with 12-week follow-up showing hypertrophy and strength gains. Casein is 'slow,' clotting in the stomach and releasing amino acids over 7–8 hours — ideal anabolic support during the fasted night.
Practical alternatives: cottage cheese, Greek yogurt, milk + nuts. Reduce or shift timing if reflux or indigestion occurs.
Does High Protein Damage the Kidneys?
The most common worry is 'high protein = kidney damage.' In healthy kidneys, there is no evidence for this.
Devries et al. 2018 in Journal of Nutrition — a meta-analysis of 28 RCTs — found no meaningful adverse effect of high protein on eGFR in healthy adults. 'Hyperfiltration' is an adaptive response, not damage. Shams-White 2017 meta found high protein neutral or beneficial for bone, correcting the old 'protein leaches calcium' myth.
Exception: those with diagnosed chronic kidney disease (CKD). Protein restriction is part of standard staged care. Anyone with suspected kidney issues, long-standing diabetes, or hypertension should set protein targets with a clinician.
Korea: Supplement Market and Diet Redesign
Korea's 2022 nutrition survey shows mean intake near 1.0 g/kg/day — meeting the RDA. But the average hides distribution problems:
- Breakfast gap: traditional Korean breakfast (rice + soup + kimchi) often < 10 g protein
- Elder deficit: 30–40% of those 75+ fall short
- Lunch/dinner skew: a 50 g bolus may exceed leucine threshold but is inefficient over 24 hours
Korea's protein drinks, bars, and powders have boomed 20%+/year for five years — gym culture, marketing, mainstreamed 'protein.' Supplements are safe tools, but 'food first, supplement to fill gaps' remains the rule. A daily mix of milk, eggs, beans, tofu, fish, and lean meat beats a tub of powder.
Conclusion: Whose Number Is It?
0.8 g/kg is the floor for an average sedentary adult. If you're a 30-something who lifts three times a week, the science says 1.2–1.6 g/kg. For a 65-year-old mother, 1.0–1.2 g/kg. For hypertrophy, up to 1.6 g/kg. 20–40 g per meal, 3–4 meals a day, animal and plant mixed, capped by a glass of milk before bed. Protein beyond the RDA isn't excess — it's design.
