Due to their favorable amino acid composition, milk proteins have a higher nutritional quality compared to vegetable proteins (eg PDCAAS of 1.27 for milk protein vs 0.92 for soy protein) 1-3.
Adult protein requirements WAO 2007, milk protein amino acid profile, Handbook Ecyclopedia of Dairy Sciences , Roginski, Fuquay and Fox p1993
Soy protein aino acid profile from Source: Renner E., Milk and Dairy Products in Human Nutrition, Munich, Germany, 1983 (http://joeskopec.com/aminos.html). Since no value is given in this reference for histidine, the histidine value for soy is derived from http://www.build-muscle-and-burn-fat.com/soy-versus-whey-protein.html.
FAO (2013) Food and Nutrition Paper 92, Dietary Protein quality evaluation in human nutrition: Report of an expert consultation. Rome: FAO.