Evaluation of the nutritional quality of dietary proteins: data and doubts.

Dietary protein quality is influenced by several factors, especially the am ino acid content, and their bioavailability. The method recommended by the FAO/WHO (1985, 1990) for dietary protein quality assessment is based on the ability of the protein to satisfy the essential amino acid requirements. T he Protein Digestibility Corrected Amino Acid Score (PD-CAAS) has been prop osed as a quality index and takes into account both the essential amino aci d composition and protein digestibility. This index can easily be routinely used but some conceptual and methodological limits must be considered, suc h as the determination of both nitrogen and essential amino acid requiremen ts, the bioavailability of dietary amino acid and the validation of the qua lity indexes.