How much protein do you actually need? A grown-up answer.

Few numbers in nutrition are quoted with more confidence and less context than the daily protein recommendation. Public health agencies publish 0.8 grams per kilogram of bodyweight. Strength coaches publish double that. Both numbers are real. Both are answers to different questions. Almost nobody tells you which question they are answering, which is how a perfectly reasonable conversation became a marketing one.

This piece walks through where each figure comes from, what the trials actually show, and how to land on a number that fits your life rather than someone else's product.

§ Where the 0.8 g/kg floor comes from

The Recommended Dietary Allowance of 0.8 grams of protein per kilogram of bodyweight per day was set by the Institute of Medicine in 2005, derived primarily from nitrogen balance studies in young adults. Nitrogen balance is a crude tool — it measures whether nitrogen consumed roughly matches nitrogen excreted, and is calibrated to prevent deficiency in the general population. The Institute itself noted at the time that the RDA was a minimum sufficient intake for healthy sedentary adults, not an optimum for performance, recovery, or healthy ageing.

Two consequences follow. First, the RDA is the right answer if the only question is 'what stops me getting sick?'. Second, it is the wrong answer for almost everyone reading this, because almost nobody is asking only that question.

§ Why the influencer numbers are not made up either

The 1.6 to 2.2 g/kg numbers you see on fitness platforms come largely from resistance-training literature. A 2018 meta-analysis by Morton and colleagues, published in the British Journal of Sports Medicine, pooled forty-nine randomised trials and found that additional dietary protein produced meaningful gains in lean mass and strength up to roughly 1.6 g/kg/day, with diminishing returns beyond that point. For trained lifters in a calorie deficit, the ceiling drifts a little higher.

These are not invented numbers. They are answers to a different question: how much protein is needed to maximise muscle protein synthesis under repeated mechanical stress? If you are not lifting heavy things, you do not need to eat as if you were.

"The honest answer is a range. The range depends on what you are asking your body to do."

§ The number most adults should actually aim for

For an adult who walks, occasionally lifts, wants to preserve muscle into their fifties and sixties, and is not deliberately dieting, the consensus across the modern literature lands between 1.2 and 1.6 grams per kilogram of bodyweight per day. A 70-kilogram person lands somewhere between 84 and 112 grams. That is, roughly, a palm-sized portion of protein at each of three meals plus a substantial snack.

This range is not radical. It is the position taken by Stuart Phillips and colleagues in a widely-cited 2016 paper in Applied Physiology, Nutrition, and Metabolism, and is consistent with the International Society of Sports Nutrition's 2017 position stand. It is roughly double the public-health RDA, which is exactly what you would expect once you remember that the RDA was never trying to answer this question.

§ Older adults need more, not less

The most consequential update to the protein conversation in the last decade concerns ageing. With age, muscle protein synthesis becomes blunter — a phenomenon called anabolic resistance. A given dose of protein produces a smaller signal in a sixty-five-year-old body than in a twenty-five-year-old body. The implication is unintuitive but important: older adults need to eat more protein per meal to get the same biological work done.

The PROT-AGE Study Group, an international consortium of geriatric and nutrition specialists, recommends 1.0 to 1.2 g/kg/day for healthy older adults and 1.2 to 1.5 g/kg/day for those with acute or chronic illness, alongside resistance exercise. ESPEN, the European clinical nutrition society, has issued broadly similar guidance. Both groups explicitly warn against applying the general-population RDA to people over sixty-five.

The clinical relevance is sarcopenia — the slow, accelerating loss of muscle mass and function that drives falls, fractures, hospitalisations, and the slow erosion of independence in the last decade of life. The literature here is not contested at the margins. The intervention is protein plus resistance training. The under-prescription is widespread.

§ Distribution matters more than the daily total

A second piece of the puzzle, often missed in the headline number, is timing. Muscle protein synthesis is a switch, not a dimmer. It is triggered by a per-meal threshold of leucine — one of the essential amino acids — which is reached at roughly 0.4 grams of protein per kilogram of bodyweight per meal in healthy adults, and somewhat higher in older adults.

Practically: four meals of 25 to 40 grams of protein each will produce more muscle protein synthesis across a day than a single 120-gram dinner. Schoenfeld and Aragon, in a careful 2018 review for the Journal of the International Society of Sports Nutrition, conclude that three to four protein-containing meals at intervals of three to five hours is a defensible target for most goals. This is not exotic eating. It is the default shape of most ordinary diets — once breakfast contains actual protein.

§ Whole food covers almost everyone

The supplement industry has a clear interest in framing protein as a problem only it can solve. The data does not really support that framing. A modestly built adult who eats eggs or Greek yoghurt at breakfast, a chicken or tofu lunch, fish or pulses with dinner, and a glass of milk somewhere in the day clears the upper end of the range without difficulty.

Powders are convenient. They are not magic. The meta-analyses that show clear benefits from protein supplementation almost universally show those benefits in people who would otherwise have been under-eating protein. If your existing meals already meet the target, the marginal benefit of a shake is close to zero.

§ What the science does not support

Several confident claims circulating in the wellness conversation are not supported by the current evidence base.

• →The body cannot use more than 30 grams of protein at a meal. This is a misreading of older absorption studies. Larger doses are absorbed and used, with a slightly slower release; the muscle-protein-synthesis response plateaus, but the rest of the protein is not wasted.
• →High protein intake damages healthy kidneys. Repeated systematic reviews in adults with normal renal function have found no causal link. The concern is real in people with established kidney disease and should be discussed with a clinician in that context.
• →Plant protein is functionally inferior to animal protein. Per gram of leucine it is somewhat less efficient at triggering muscle protein synthesis, which matters at the margins. A varied plant-forward diet that hits the daily total works perfectly well; this is now well demonstrated.

§ A simple framework

Pick a target inside the 1.2–1.6 g/kg/day range based on age and activity. Spread it across at least three meals, each clearing roughly a palm-sized portion of a protein-dense food. Lean toward the upper end if you are over fifty, training with weights, recovering from illness, or losing weight. Lean toward the lower end if you are young, sedentary, and not trying to change your body composition. Adjust based on how you feel and how your strength is trending over months, not days.

That is the grown-up answer. It is less satisfying than a slogan, which is why the slogans keep winning. Take the slower answer anyway. Your future hips will thank you.