Did you know that up to 30 % of the protein you eat can be ineffective for muscle synthesis if its amino acid profile is incomplete? A 2022 meta‑analysis in Journal of the International Society of Sports Nutrition found that athletes consuming low‑quality protein sources needed ≈ 1.6 g/kg more total protein to achieve the same muscle‑protein synthesis rates as those eating high‑quality proteins.
What Is the Protein Quality Index?
The protein quality index (PQI) quantifies how well a dietary protein meets human amino acid requirements, focusing on digestibility and the completeness of its essential amino acid (EAA) profile. Two mainstream scoring systems are used:
- PDCAAS (Protein Digestibility‑Corrected Amino Acid Score) – the older WHO/FAO method, capped at 1.0.
- DIAAS (Digestible Indispensable Amino Acid Score) – the newer FAO recommendation, values can exceed 1.0 for exceptionally high‑quality proteins.
