Metabolic response to egg white and cottage cheese protein in normal subjects

In type II diabetic subjects, we previously demonstrated differences in the serum insulin, C-peptide, and glucagon response to ingestion of seven different protein sources when administered with 50 g of glucose. The response was smallest with egg white and greatest with cottage cheese protein. In the present study, we compared the responses to 50 g of the above two proteins ingested without glucose in normal male subjects. We also determined the proportion of each ingested protein converted to urea nitrogen. The incremental area response integrated over 8 hours for serum insulin, C-peptide, glucagon, alpha-amino-nitrogen (AAN), and urea nitrogen were all approximately 50% less following egg white. This was associated with a 50% smaller conversion of protein to urea. Overall, 70% of the cottage cheese but only 47% of the egg white protein could be accounted for by urea formation. Most likely the smaller hormonal response to egg white is due to poor digestibility of this protein.