Complete Protein

A complete protein contains all nine essential amino acids — the ones the body cannot make — in amounts that make it a standalone protein source. Animal proteins (whey, casein, egg, meat) and soy are complete; most single plant sources are not, which is why plant powders blend them. It is a protein-quality fact, not a ranking of foods by worth: an incomplete protein in a varied diet is not a problem, and "complete" on a label is a claim about the amino profile, nothing more. Protein-quality scores like PDCAAS and DIAAS put numbers on this.