Protein quality malnutrition

Authors: MANARY, MARK - Children'S Nutrition Research Center (CNRC); WEGNER, DONNA - Washington University; MALETA, KENNETH - Non ARS Employee

Submitted to: Frontiers in Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/11/2024
Publication Date: 10/23/2024
Citation: Manary, M.J., Wegner, D.R., Maleta, K. 2024. Protein quality malnutrition. Frontiers in Nutrition. 11. Article 1428810. https://doi.org/10.3389/fnut.2024.1428810.
DOI: https://doi.org/10.3389/fnut.2024.1428810

Interpretive Summary: Protein quality malnutrition occurs when diets chronically fail to deliver sufficient amino acids to support physiological functions, with current protein quality scoring systems like PDCAAS and DIAAS comparing a food's amino acid composition to requirements of healthy individuals, which may not accurately reflect the increased demands or altered metabolism experienced by malnourished children. Through analysis of protein metabolism studies and clinical feeding trials in malnourished Malawian children, researchers found that metabolic adaptation to malnutrition reduces protein kinetics (conserving amino acids but decreasing capacity to respond to infection), and that milk protein consistently outperforms vegetable proteins in promoting recovery, even when protein quality scores are similar, suggesting factors beyond standard protein quality metrics affect clinical outcomes. This research illuminates the complexities of protein metabolism in malnutrition by demonstrating that milk protein's superior clinical performance likely stems from bioactive peptides created during casein digestion that provide anti-inflammatory, antioxidant, and antimicrobial benefits through specific gut receptors, indicating that the source of dietary protein is a critical consideration beyond protein quality scores when treating malnourished children.

Technical Abstract: Protein quality refers to the evaluation of a food or a diet based on its amino acid composition, protein digestibility, and protein bioavailability. When these parameters are specified, either through direct measurement or estimation, the amino acids provided by the diet are compared to those required by a healthy individual, and based on this comparison, an adequacy ratio or score is assigned. Two widely used protein quality scoring systems are the protein digestibility-corrected amino acid score (PDCAAS) and the digestible indispensable amino acid score (DIAAS), neither of which account for the dietary source of the protein. In malnourished children, metabolic adaptations reduce the endogenous availability of amino acids and increase the demand for protein synthesis. These increased amino acid requirements are primarily driven by the presence of acute infection and the need for tissue accretion. This review examines two large clinical feeding trials involving moderately malnourished children, where dietary protein quality was carefully measured. The finding s suggest that protein quality scores alone do not reliably predict weight gain or recovery in these children and that consuming milk protein provides distinct advantages over vegetable-based proteins.