Protein: the target you're not hitting

Patrícia is 47, a banking executive, mother of two teenagers. Weighs 64 kg (141 lbs). Disciplined with food — I eat healthy, doctor. Breakfast: black coffee, a piece of fruit, sometimes a light yogurt. Executive lunch: large salad, grilled chicken, brown rice. Dinner: leftovers or soup. Has done Pilates twice a week for eight years.

I asked for a three-day food diary with weighing. The nutritionist calculated. Average protein intake: 51 g/day. For her weight, that is 0.8 g/kg. DEXA bone density: lumbar-spine osteopenia. Lean mass: lower quartile for age and height. Grip strength: 22 kg — borderline.

Patrícia is the common case. It is not negligence. It is a poorly explained RDA and a food industry that sells “healthy” as a synonym for low calorie.

The RDA is the floor, not the ceiling

The American Recommended Daily Allowance (RDA) for protein in adults is 0.8 g/kg/day. That number, repeated for fifty years, was calculated to prevent negative nitrogen balance in young, sedentary, healthy adults. It answers the question “what is the minimum quantity below which the body begins to cannibalize itself?” It does not answer the question “what is the ideal quantity to preserve lean mass, strength, and bone density across decades?”

These two questions have different answers — and the literature of the last fifteen years has been clear in distinguishing them.

The Stuart Phillips and colleagues review in Applied Physiology, Nutrition, and Metabolism (2016) synthesizes the evidence: to optimize long-term health, especially the preservation of lean mass, healthy adults benefit from 1.2 to 1.6 g/kg/day. In specific contexts — elderly, sarcopenic, in strength training, intentional weight loss — the band can rise to 1.6 to 2.2 g/kg/day.

The PROT-AGE position paper, published by Jürgen Bauer and colleagues in the Journal of the American Medical Directors Association in 2013, is more conservative: at least 1.0 to 1.2 g/kg/day for healthy adults >65 years old, and 1.2 to 1.5 g/kg/day for the elderly with acute or chronic disease. The ESPEN position by Nicolaas Deutz and colleagues (2014) reaches the same conclusions with more emphasis on combined exercise.

Patrícia, at 0.8 g/kg, sits in the band that covers basic biochemistry survival. She is not in the band that preserves her body for the next forty years.

Why after 40 the target rises

A phenomenon called anabolic resistance happens with age. The muscle of an older adult responds less to the same quantity of protein (and less to the same quantity of exercise) than the muscle of a young adult. To generate the same myofibrillar protein synthesis, more signal is needed — more essential amino acids, especially more leucine, per meal.

The Daniel Moore and colleagues study, published in J Gerontol A Biol Sci Med Sci (2015), showed that older men need approximately 0.40 g/kg of protein per meal to maximize muscle protein synthesis, against 0.24 g/kg in young men. For a 65 kg woman, that means about 26 g of protein per meal just to trigger the signal — and more to sustain it.

The Robert Morton and colleagues meta-analysis, published in the British Journal of Sports Medicine in 2018, aggregated 49 randomized trials and showed that supplementing protein in those who already train strength significantly increases the gain of lean mass and strength — with the effect diminishing after total intake reaches approximately 1.6 g/kg/day. Above that point, more protein does not give more muscle.

This defines a clear operational window: for most adults >40 who train strength and want to preserve (or gain) lean mass, 1.2 to 1.6 g/kg/day, distributed across three to four meals of at least 25 to 30 g of protein each, is the target band.

Leucine is the trigger

Among the essential amino acids, leucine directly activates the mTORC1 pathway — the molecular switch of muscle protein synthesis. The literature suggests a threshold: about 2.5 to 3 g of leucine per meal is the point at which synthesis is maximized in older adults. That threshold corresponds, on average, to 25–30 g of high-quality protein (high biological value).

The important detail: 30 g of protein in a single meal does more for muscle synthesis than 90 g divided across four meals of 22 g each. Distribution matters — but with a floor. A meal below the leucine threshold does not count as “anabolic stimulus.”

How much each food has (really)

The practical problem: most people poorly estimate how much they consume. Some references per portion:

• Grilled chicken, 100 g: 31 g of protein.
• Fish fillet (tilapia, salmon), 100 g: 22–25 g.
• Lean beef, 100 g: 26 g.
• 1 large egg: 6 g (the white has ~3.5 g).
• Whey protein, 30 g of powder: 22–25 g.
• Plain unsweetened Greek yogurt, 170 g: 17 g.
• Cottage cheese, 100 g: 11 g.
• Cooked lentils, 1 cup: 18 g (with lower digestibility than animal protein).
• Firm tofu, 100 g: 12–15 g.

Patrícia, in her diary, had a breakfast with 3 g of protein, lunch with 32 g, and dinner with 16 g. Breakfast was well below the leucine threshold — her body spent the entire morning in catabolic state until lunch. Simple change: replace coffee-with-fruit with two eggs + Greek yogurt + a piece of fruit. Breakfast climbed to 25 g without significantly increasing total calories.

On the “kidney overload” story

Repeated for decades, the idea that high-protein diets “overload the kidney” applies to patients with established chronic kidney disease — not to adults with normal renal function. In healthy adults, protein intakes of 1.2 to 2.2 g/kg/day, maintained for months to years, were not associated with kidney function decline or alteration of creatinine or estimated glomerular filtration rate in prospective studies. The caution applies to those who already have diagnosed disease — where the discussion is with a nephrologist — not to the general population.

The reading the Continuum makes

In Continuum Plenya, the protein target is designed case by case, with weight, body composition, kidney function, training type, and the patient's eating pattern. The nutritionist calculates the per-meal distribution, suggests practical combinations (the “standard” executive lunch is not the goal, it is the starting point), and adjusts at quarterly reassessments. Patrícia, from the beginning of the story, today consistently hits 1.4 g/kg. In six months she gained 2.1 kg (4.6 lbs) of lean mass, grip strength climbed to 28 kg, ferritin went from 41 to 79 ng/mL.

Eating “healthy” is not the same as eating enough. For the body that needs to cross thirty years from 50 onward, protein is the material with which it sustains itself — and the material that most often is missing from the plate.