Comparative Protein Value of Several Vegetable Protein Products Fed at Equal Nitrogen Levels to Human Adults

The objective of the current study was to determine the protein nutritional value of several vegetable protein products processed to resemble ground beef. The test products were soy protein products, each made by slightly different extruded methods of industrial processing using basically either the defatted soy flour or the soy concentrate protein and a blended wheat protein product. Ground beef and dried whole egg were used as comparative control proteins. The human metabolic study was 32 days in length. Nine subjects were fed 4.Og N from the test products plus 0.8g N from the basal diet. Caloric intake was adjusted to maintain normal body weight. The test products were assigned at random. The protein nutriture of the subjects was evaluated by the nitrogen balance technique. Fasting venous blood samples were taken at the beginning and end of each experimental period. Results showed that the mean nitrogen balance of subjects fed extruded defatted soy flour protein, extruded soy concentrate protein and blended wheat protein products were—1.16,—1.31 and ‐0.99, respectively, as compared to the standard controls beef and egg, which were—0.42 and ‐0.34, respectively. There was a significant difference in the nitrogen balance of the standard controls and the test products but not among them. Wheat protein product which was supplemented with lysine had significantly better apparent digestibility than the soy protein products. Mean blood constituent data show that a11 values of ail subjects were within the normal range throughout the study with the exception of triglyceride for a few individuals. The egg diet resulted in a significant rise in the blood triglyceride levels over values when other diets were fed. Blood cholesterol values tended to be higher when egg, beef or normal diets were fed than when the vegetable protein diets were consumed.