American Journal of Clinical Nutrition, Vol 25, 912-915, Copyright © 1972 by The American Society for Clinical Nutrition, Inc.

Comparative utilization of casein-lactalbumin and spun soy protein diets by human subjects

¹ From the Department of Home Economics, University of Vermont, College of Agriculture and Home Economics, Burlington, Vermont 05401

The utilization of freeze-dried spun soy protein was compared with that of casein-lactalbumin with both proteins adjusted to the FAO provisional pattern, using crystalline amino acids in two studies with young men. Criteria of utilization were nitrogen balance, urea nitrogen and ammonia nitrogen excretion, with 15-day test periods and a cross-over experimental design.

In the first study, 0.4 g protein/kg body wt per day was fed. There were no significant differences between treatments for all three criteria comparing the last 10-day means on each protein. However, the mean nitrogen balance for all subjects was substantially more negative on the last 10 days of the second period than on the first period, with a difference close to the 5% level of significance.

In the second study, 0.45 g protein/kg body wt per day was fed. Again there were no significant differences between treatments for all criteria. However, the mean negative balance was reduced to near equilibrium and showed no significant difference between the two periods.

These studies show that spun soy protein and casein-lactalbumin appear to be equally well utilized when supplemented with crystalline amino acids to the same pattern of amino acids.