Why one protein target does not fit everyone

Protein has turned into a number people carry around like a moral score. Hit the target and the day feels disciplined. Miss it and the unease starts: not enough for muscle, not enough for aging well, not enough for metabolic health. That logic works neatly on a shaker cup. It works less neatly in real bodies.

That tension sits at the centre of new reporting from Texas A&M and the underlying 2025 Clinical Nutrition paper by Nicolaas E. P. Deutz, Robert R. Wolfe and Mariëlle P. K. J. Engelen. The authors are not arguing that protein suddenly matters more than it did last year. What they are saying is that the way nutrition science has long estimated protein requirements may smooth over differences that matter in practice — age, training status, illness, energy balance, and the constant churn of protein inside tissues.

The new work does not prove everybody should chase bigger macros. It does challenge the idea that one public-facing daily target can do every job at once. Consider the logic: a number designed to prevent deficiency at the population level is not automatically the number that best supports an older adult trying to hold on to muscle, or an active person dieting while still lifting, or a patient whose appetite has collapsed on a weight-loss drug.

Deutz put the point plainly in the Texas A&M coverage: “We need to think more on an individual basis. You cannot take one value.” That line travels well because it speaks to a real frustration. Protein advice often gets flattened into a social-media contest between camps. One side treats the current recommended dietary allowance as laughably low. The other talks as if anything above it is hype. The actual literature is messier — which is another way of saying more interesting.

What the new protein paper is actually arguing

The Deutz et al. paper in Clinical Nutrition is partly a methods paper and partly a challenge to old assumptions. Traditional protein recommendations were built largely from nitrogen-balance studies, work that tried to estimate need by measuring nitrogen in and nitrogen out. That approach shaped the familiar 0.8 g/kg/day RDA, still the headline number most consumers see.

Nitrogen balance can miss part of the picture, Deutz and colleagues argue, because it does not capture intracellular protein turnover well. Their alternative uses pulse stable-isotope tracers and compartmental modelling. A related 2024 mini-review in Frontiers in Nutrition by Engelen and Deutz says these tracer methods may do a better job estimating protein breakdown and meal response in both health and critical illness. If the older method undercounts turnover, the resulting requirement estimate may also be too low for some people.

One number from the concept paper helps explain why the authors think the field may be missing something. The model estimated net daily protein losses at about 87 g/day. That is not a universal intake prescription — it is a signal about flux. Human protein metabolism is dynamic, and the cost of replacing losses does not fall evenly across all adults in all circumstances.

That nuance matters. Methods stories often get flattened into a false before-and-after: old number bad, new number good. The new paper is not a giant randomized feeding trial that settled the question for everybody. It argues the measurement tool itself may be part of the disagreement. That is still consequential. If the measuring tape is crude, the confident advice built on top of it may also be crude.

Why the old benchmark still survives

The case for individualisation does not mean the current RDA was meaningless. In a Stanford Medicine explainer, nutrition researcher Christopher Gardner made a point that often disappears from internet debates: the 0.8 g/kg/day figure was designed to cover the needs of almost all adults, not to function as a competitive target for physique culture. Stanford’s reporting also notes an estimated average requirement of 0.66 g/kg/day, with the higher RDA acting as a safety margin.

Gardner’s wording is worth lingering on. The figure, he said, “was designed to meet the needs of 98% of American adults” and “shouldn’t be viewed as a minimum to ‘beat.’” It is a useful corrective to supplement marketing, which often treats the public-health number as embarrassingly outdated so every new tub of powder looks essential. The RDA still answers a real question. It is a baseline meant to prevent inadequacy in the general population.

But baseline is not the same as optimal for every goal. A healthy thirty-year-old who is sedentary, weight stable, and eating enough total calories is in a different situation from a seventy-year-old with low appetite. Or somebody training hard while cutting calories. Or somebody recovering from illness. Once those contexts enter the picture, the conversation stops being about one sacred number and becomes clinical.

Who may need more than the headline target

Older adults sit near the centre of this debate because muscle becomes harder to maintain with age. An older person can clear the RDA on paper and still struggle with sarcopenia, low appetite, dental issues, or the simple fact that eating enough protein at each meal becomes less automatic over time. That concern did not begin with the new Texas A&M paper.

A 2015 Journal of Nutrition study by C. W. Bales and C. S. Ritchie, using the indicator amino acid oxidation technique, estimated an average requirement of 0.96 g/kg/day in women older than sixty-five, with the upper 95% confidence interval reaching 1.29 g/kg/day. That does not create a universal target for all older adults. It does show why some clinicians and dietitians have been uneasy with the idea that one broad population number settles the issue.

Stanford Medicine’s Marily Oppezzo makes the real-world version of that point. Older adults and people losing weight may need more protein to preserve lean mass, she said, but protein is not magic on its own. “The biggest thing that stops muscle loss is strength training.” That sentence should probably be stapled to half the protein discourse online. More grams do not cancel out inactivity. They also do not guarantee muscle retention when total energy intake is too low or illness is dragging appetite down.

The same caution applies to active people. Coverage of the new paper and related expert commentary often points to ranges around 1.2 to 1.6 g/kg/day for athletes or other specific groups. Those numbers may be reasonable in context. They are also easy to misuse. A range built for training adaptation, recovery, or dieting under load is not a general instruction for every office worker who saw a high-protein meal plan on TikTok.

What the protein boom gets right, and wrong

The current protein boom is not pure nonsense. It responds to a real shift in the evidence base — away from thinking only about deficiency diseases and toward function: muscle retention, satiety, recovery, and aging. Readers are not wrong to notice that the conversation has moved.

Modern protein culture, though, often behaves as if uncertainty itself has disappeared. A person plugs weight into an app, gets one daily gram total, then shops as if that number arrived from a scanner rather than a patchwork of population studies, performance research, and practical compromises. The NPR explainer on protein intake captures why the confusion persists. The question is easy to ask in public but hard to answer without knowing age, training, goals, health status, and how much food someone can realistically eat.

This is also where the new tracer work is most helpful, even before it changes formal guidelines. It reminds readers that protein need is not a personality test. It is a context-dependent biological question. The best intake for a sedentary adult trying simply to avoid inadequacy may differ from the best intake for a postmenopausal lifter, and both may differ again from the best intake for somebody on a GLP-1 drug who is unintentionally eating very little. A single macro target can be a useful starting point. It becomes misleading when it pretends to be a full diagnosis.

There is another quiet implication here. If requirement estimates become more individual, food quality and eating pattern matter more too. Someone who spreads protein across meals, gets enough total calories, and continues resistance training may solve a muscle-maintenance problem very differently from someone who tries to solve it with one large shake at night. The new paper does not settle meal timing. It does argue for a more adult frame: first identify the problem, then match the protein strategy to it.

Where this leaves a reader right now

The safest conclusion is not glamorous. The old benchmark still has value. The new research suggests it may not be enough detail for every life stage or goal. Both of those things can be true at the same time.

For readers, that means treating the RDA as a public-health floor rather than a universal performance prescription, and treating higher targets as context-specific rather than inherently superior. It also means resisting the idea that more is always better. Protein powders can be convenient. They are not evidence by themselves. Anyone considering a major increase in protein intake — especially older adults, people with kidney disease, or people eating much less because of illness or weight-loss medication — should discuss it with a clinician or dietitian first.

The deeper lesson from Deutz and colleagues is not that nutrition science failed to notice protein until the influencer era. It is that a mature field keeps revisiting how it measures what matters. Sometimes the new finding is a nutrient. Sometimes it is the ruler.

And if that ruler is changing, the practical question for readers becomes less theatrical and more useful. Not how much protein is everyone supposed to eat. Who, exactly, is the number for?

References

1. Deutz NEP, Wolfe RR, Engelen MPKJ. A new concept to establish protein requirements. Clinical Nutrition. 2025. https://www.sciencedirect.com/science/article/abs/pii/S0261561425000378
2. Engelen MPKJ, Deutz NEP. Compartmental analysis: a new approach to estimate protein breakdown and meal response in health and critical illness. Frontiers in Nutrition. 2024. https://www.frontiersin.org/journals/nutrition/articles/10.3389/fnut.2024.1388969/full
3. Bales CW, Ritchie CS. Dietary protein requirement of female adults >65 years determined by the indicator amino acid oxidation technique is higher than current recommendations. The Journal of Nutrition. 2015. https://www.sciencedirect.com/science/article/pii/S0022316622085820