Protein

What is protein?

Protein is a polymer of amino acids folded into a functional shape by the sequence of its constituent residues. Nine of the twenty proteinogenic amino acids are essential — the body cannot synthesise them and must obtain them from food. In dietary terms, protein delivers 4 kcal per gram and supplies the nitrogen the body uses to build muscle, connective tissue, enzymes, and antibodies, and to keep the plasma amino-acid pool from being depleted between meals.

How much do you need?

The RDA is a floor, not a target — it is the intake at which about 97.5% of the population will avoid negative nitrogen balance. The higher numbers in trained, older, or dieting adults reflect measurably better outcomes on function-level endpoints (lean mass retention, strength, gait speed), not just nitrogen balance.

Where protein comes from

• Animal foods: meat, poultry, fish, eggs, dairy. Complete amino-acid profiles, high digestibility (DIAAS > 1.0 for most cuts and dairy).
• Legumes and pulses: beans, lentils, chickpeas, soy, edamame. Lower in methionine than animal foods but paired with grains across the day the shortfall closes.
• Whole grains, nuts, seeds: secondary contributors; higher in lysine when combined with legumes.
• Manufactured isolates: whey, casein, soy, pea, rice, hemp protein isolates. Grams of protein per calorie are unmatched, and they are the archetypal NOVA Group 4 ingredient.

Distribution and quality

Muscle protein synthesis peaks around 0.3–0.4 g/kg per meal (Moore, American Journal of Clinical Nutrition 2009;89:161–168; Schoenfeld & Aragon 2018). Spreading intake across three or four meals of that size beats loading it into one large dinner, particularly in adults over 60 where "anabolic resistance" raises the per-meal threshold.

Quality is captured by two measures: PDCAAS (older, capped at 1.0) and the newer DIAAS published by the FAO (2013 report on Protein Quality Evaluation). Whole milk, egg, whey, and soy isolate score at or above 1.0; wheat, rice, and most single plant sources score 0.4–0.9 in isolation but rise sharply in mixed diets.

Protein in ultra-processed foods

Because isolates are cheap and functionally flexible, "high-protein" packaging usually signals a Group 4 formulation: bars, shakes, snack puffs, protein cereals. These products meet the macronutrient number on the label but arrive with emulsifiers, sweeteners, and flavour systems — the same additive profile Monteiro (2019) uses to identify UPF. The Hall randomised feeding trial (Cell Metabolism 2019;30:67–77) showed that even calorie- and protein-matched UPF diets drove +508 kcal/day of spontaneous intake versus a whole-food comparator.

How NakedCalorie treats protein

Absolute protein content is not scored directly — a food does not get a higher score for being "high protein". Protein-isolate ingredients on the label do count toward NOVA Group 4 classification. See protein isolates for the ingredient-level view, carbohydrates and dietary fats for the other macros, and Group 4 ultra-processed foods for why the formulation matters more than the protein number.