From a digestibility point of view soy, egg whites, casein, milk and whey have a digestibility of 1.0 measured using the 'Protein Digestibility Corrected Amino Acid Score'(PDCAAS). This is a method of evaluating the protein quality based on the amino acid requirements of humans. Things like beans, peanuts, beef and lentils are not as digestible and have PDCAAS between 0.52 and 0.68.