Is the recommended daily allowance for protein too low?
It answers a narrower question than most people think. The 0.8 g/kg figure is the intake at which almost nobody loses body nitrogen, derived from balance studies, so it is a floor for avoiding deficiency. A newer method puts the requirement higher, and the expert groups already recommend more for older adults and for people training.
Key takeaways
- The RDA is 0.8 g per kilogram a day, and it is a floor for preventing deficiency rather than a target for good outcomes.
- It came from nitrogen balance studies, which measure whether you are losing body nitrogen, not whether you are thriving.
- A different method, indicator amino acid oxidation, has repeatedly landed higher: around 1.2 to 1.3 g/kg in the groups tested.
- The expert groups have not waited for the RDA to move: 1.0 to 1.2 g/kg over 65, and 1.4 to 2.0 for people training.
- None of this makes the RDA wrong. It makes it an answer to a question most people are not asking.
Almost every argument about protein intake is really an argument about this one number, so it is worth being precise about what it is.
What the RDA is an answer to
The Recommended Dietary Allowance for protein is 0.8 g per kilogram of body weight a day for healthy adults, set in the 2005 Dietary Reference Intakes.1
It was derived from nitrogen balance studies. Protein is the only macronutrient containing nitrogen, so measuring nitrogen going in against nitrogen coming out tells you whether the body is holding its own. Find the intake where balance is reached for nearly everyone, and you have the RDA.
Read that method back and the limits are visible in it. It answers: below what intake do people start losing body nitrogen? It does not answer: at what intake do people keep the most muscle, recover best, or age with the most strength? Those are different questions and nitrogen balance was never built to reach them.
The report itself is careful about this. It set the acceptable range at 10 to 35 percent of energy from protein, and declined to set an upper limit at all, saying there was no evidence base from which to derive one.1
What a different method finds
The main alternative is indicator amino acid oxidation, which tracks how the body handles a marker amino acid as protein intake varies. Where nitrogen balance asks whether you are losing ground, this asks at what point the body stops burning off an indicator because it finally has enough to build with.
It lands higher, consistently.
| Nitrogen balance (the RDA) | Indicator amino acid oxidation | |
|---|---|---|
| Average requirement | 0.66 g/kg/day | 0.96 g/kg/day |
| The figure covering nearly everyone | 0.80 g/kg/day | 1.29 g/kg/day |
Those numbers come from a study of women over 65, and the gap between the columns is about 60 percent.2 A 2023 review lays out the broader argument that the current US recommendations are due for reconsideration on these grounds.3
Two honest caveats belong with that table. The study was small, and one method landing higher than another is an argument for revising a guideline, not a revision. The RDA has not moved.
The expert groups did not wait
The more useful observation is that nobody working on ageing or sports nutrition treats 0.8 as the operating number anyway.
- PROT-AGE, 2013: at least 1.0 to 1.2 g/kg/day for healthy adults over 65, and 1.2 to 1.5 with acute or chronic illness.4
- ESPEN, 2014: the same range, reached independently.
- Sports nutrition guidance: 1.4 to 2.0 g/kg/day for people training to build or keep muscle.
None of these contradict the RDA. They sit above it, for populations the RDA was not written about, and they have been in place for over a decade.
What this means for your number
Less than the framing of the debate suggests, and it is worth saying so plainly rather than turning a methods argument into a reason to eat much more.
Going from 0.8 to 1.2 g/kg is about a third more protein, not double. For a 70 kg adult that is 56 g against 84 g: one additional proper serving in the day, usually at breakfast, which is where almost everyone's shortfall lives.
And it is one third more of a nutrient with no demonstrated upper limit in healthy adults, which is a question worth answering separately rather than assuming in either direction.
The recommendations by situation, and how to turn a per-kilogram rate into grams, are in how much protein you need per day.
Where the general argument stops applying
All of the above is about healthy adults. If your kidney function is reduced, if you have liver disease, or if protein is already managed as part of your treatment, then the number is a clinical decision and the debate on this page is not yours to settle from a website. Take it to the clinician who has your history.
More questions about Protein basics
Has the RDA actually changed?
No. It has been 0.8 g per kilogram of body weight a day for healthy adults since the 2005 Dietary Reference Intakes and has not been revised. What has changed is that professional groups working on ageing and on sports nutrition publish higher figures for the populations they cover, and those sit alongside the RDA rather than replacing it.
What is wrong with nitrogen balance?
Nothing, for the question it asks. It measures whether nitrogen in matches nitrogen out, which detects a deficit. It is less good at finding the intake associated with better muscle, recovery or function, and it tends to underestimate requirements because of how losses are measured and extrapolated. It answers where the floor is, not where you want to be.
Does this mean I should eat much more protein?
It means the floor is not the target, which for most people is a moderate change rather than a dramatic one. Going from 0.8 to around 1.2 g/kg is roughly a third more, not double. Where your own figure lands depends on age, weight and whether you train, and anyone managing a medical condition that touches protein should take the question to their clinician rather than to a calculator.
References
- Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids
- Dietary protein requirement of female adults >65 years determined by the indicator amino acid oxidation technique is higher than current recommendations
- Is It Time to Reconsider the U.S. Recommendations for Dietary Protein and Amino Acid Intake?
- Evidence-based recommendations for optimal dietary protein intake in older people: a position paper from the PROT-AGE Study Group
