Protein and amino acids
Proteins are chains of amino acids folded into working shapes. The sequence of those building blocks helps determine what a protein does, from carrying out chemical reactions to forming part of a cell’s structure.
From chains to building blocks
A protein’s primary structure is the order of its amino acids. That sequence influences how the chain folds and how it interacts with other molecules. During digestion, dietary proteins are broken into smaller peptides and amino acids; those products can then enter the body’s amino acid pool for new protein synthesis or other metabolic routes.
The body continually makes and breaks down proteins. The amino acids released from food and existing proteins can be reused, while some are used in other chemical pathways.
Essential means dietary supply
The body can make some amino acids, while others must come from food. The latter are called essential or indispensable amino acids. The commonly listed nine are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. “Essential” describes the source requirement; it does not rank one amino acid as more valuable than another.
Foods provide mixtures of amino acids in different proportions. Total protein tells you the overall amount; an amino acid profile describes the building blocks within it.
Reference values are population tools
EFSA’s adult protein values use body weight: it reports an Average Requirement of 0.66 g per kilogram per day and a Population Reference Intake of 0.83 g per kilogram per day for high-quality protein. These are reference values for healthy populations, with assumptions about protein quality and usual mixed diets.
EFSA did not set separate reference values for individual indispensable amino acids. Its protein reference applies to healthy adults; needs in growth, pregnancy and lactation are considered separately.
References
Source-checked educational draft. Human editorial review pending.
NIH National Library of MedicineBiochemistry, Primary Protein StructureSource accessed 2026-09-05NIH National Library of MedicineBiochemistry, Essential Amino AcidsSource accessed 2026-09-05NIH National Library of MedicineBiochemistry, Protein CatabolismSource accessed 2026-09-05European Food Safety AuthorityScientific Opinion on Dietary Reference Values for proteinSource accessed 2026-09-05