856 



XIV. NUTRITIONAL VALUE OF FATS 



man as occurs with rats, insofar as the effectiveness of fat in protecting 

 the endogenous protein level is concerned. Thus Schwimmer and Mc- 

 Gavack^^ demonstrated that the ingestion of fat results in the maintenance 

 of a low level of urinary nitrogen in human subjects who partook of pro- 

 tein-free diets in amoimts considerably below that necessary for caloric 

 equilibrium, while fat-free diets did not exhibit this behavior under similar 

 experimental conditions. The sparing effect of fat on protein is exhibited 

 not only in relation to nitrogen minimum but also under several other 

 conditions. Thus, when rats were previously fed on diets containing 80% 

 of one foodstuff for a period of twenty-eight days and then were fasted 

 according to the procedure of Samuels et al.,^^ those which had previously 

 received the high-fat regimen subsequently excreted the smallest propor- 

 tion of nitrogen in the urine during the fast period, and apparently had the 

 most economical utilization of the protein during this time. The data for 

 these experiments on the several types of foodstuff are included in Table 3. 



Table 3 



The Average Nitrogen Excretion of Rats on Special Diets 



AND during a Subsequent Period of Fasting with 



Voluntary Activity, and of Rats Undergoing 



Violent Exercise" 



" Adapted from L. T. Samuels, R. C. Gilmore, and R. M. Reinecke, J. Nutrition, 36, 

 639-651 (1948). 



'' Including Standard Error of the Mean. 



An inspection of Table 3 will indicate that the amount of nitrogen ex- 

 creted in the group which had previousl}^ received the fat diet was in- 

 variably considerably less than that of those which had received carbo- 

 hydrate ; this in turn was considerably lower than that for the group which 

 had been fed protein. Moreover the nitrogen excretion in mg. per hun- 



