How much protein do I actually need?

Seven answers, and the spread is mostly explained by who each is addressing. Gardner is answering a population adequacy question about the average American adult, who is not training and already eats about twice the requirement. Hill publishes two numbers for two different people, 1.0 to 1.3 g/kg for a general adult and at least 1.8 g/kg for a plant-based athlete training for hypertrophy, and treats the missing training rather than the missing protein as the western problem.

Roll's figure comes from a male endurance athlete in his forties training 20 to 30 hours a week, with no study behind it. Lyon and Inchauspé are both advising an ageing adult, usually over 40 and often a woman in or near menopause, whose risk is lost muscle and bone, and Inchauspé pairs her target with three resistance sessions a week rather than issuing it alone. Attia writes for people who lift and want maximum muscle. Topol writes for older adults whose main risks are cardiovascular and neurodegenerative, and his safety argument is specifically about habitual high intake sustained for decades.

Nobody here is addressing people with reduced kidney function, where the answer is different again, and only Inchauspé names an upper limit at all. Gardner's own record carries an older-adult safety flag for the same reason: the sarcopenia literature is where the population-adequacy framing is weakest and he does not address it in the source.

Wider than a seven-way spread suggests. All of them treat the RDA as a floor set to prevent deficiency rather than an individual optimum, and the argument is about what follows from that. Gardner, Lyon and Inchauspé all state that the amino acid content of protein is the same regardless of source, and nobody here disputes it.

Nobody treats protein as the thing that does the work: Hill's whole case is that the training is the part people are missing, Lyon says protein and resistance training are inseparable, Roll treats training as the thing protein serves, and Topol's objection is specifically to added protein on top of resistance training. The numbers converge more than the headlines do, and 1.6 g/kg is where they meet: it is the top of Topol's defended band, the bottom of Attia's, and the plateau the meta-analytic literature keeps landing on.

Neither Gardner nor Inchauspé recommends protein products as a first resort; he tells readers to stop buying them and she gives buying advice only to people already using powder.

For Gardner and Hill: outcome trials in general adults showing function or mortality benefits from intakes well above the RDA with training held constant, which is the comparison the existing meta-analyses do not isolate. For Lyon, Inchauspé and Attia: a demonstration that the higher end of their range adds nothing over roughly 1.6 g/kg once resistance training is present, which is the plateau the meta-analytic literature already points at, and which Inchauspé herself cites for older adults before going above it.

For Topol: adequately powered randomised trials showing that added protein improves muscle or function on top of resistance training in adults over 50, since his objection rests on ten Haaf and colleagues finding it does not.

Running the other way, prospective evidence that habitual intake above roughly 1.6 g/kg raises cardiovascular events would move Attia, since the harm signals are observational and mechanistic rather than trial-derived. For Roll: any evidence beyond his own body, since he cites none. All of them would move faster on hard outcomes, fracture, disability and mortality, than on body composition.