FATS, CARBOHYDRATES, AND ALBUMINS. 345 



the problem from this standpoint. During one period, the food contained 

 16.08 grams nitrogen, 44 grams fat, and 466 grams carbohydrates; and 

 in a parallel experiment it contained 16.08 grams nitrogen, 146 grams fat, 

 and 250 grams carbohydrates; each gives the same number of calories 

 (2867 and 2873 calories). In both experiments practically the same 

 nitrogen balance was reached. It appears that under these conditions 

 the carbohydrates are isodynamic with the fats in respect to acting as 

 albumin sparers. Landergren * explains the greater sparing of albumin in 

 an exclusively carbohydrate diet, as compared to a diet of fats alone, by 

 the assumption that the animal organism constantly requires sugar; and 

 inasmuch as he does not believe fat can be changed into sugar, a part of 

 the albumin must be utilized, in the case of a fat diet, for the formation 

 of sugar. This part of the albumin is spared, if the food contains carbo- 

 hydrates, so that the organism then has more albumin at its disposal for 

 its remaining functions. The total albumin may be utilized as such, when 

 sufficient fat and carbohydrate has been added to the diet. This expla- 

 nation is at present only an hypothesis. 



The results as a whole, which have been obtained in studying the rela- 

 tions of the carbohydrates and fats to the transformation of albumin, 

 show that we may conclude with a great degree of probability that the 

 Law of Isodynamics holds for these nutrients among themselves. Both 

 are able to spare albumin to about the same extent. The fact that the 

 feeding of carbohydrate alone, or fat by itself, should have shown a differ- 

 ence in favor of the former, may be explained by the assumption that this 

 Law of Isodynamics is not an absolute one; i.e., the -chemical composition 

 of the foods undoubtedly plays an important part. 



We have already mentioned the most important relations existing 

 between the nitrogen-free nutrients; i.e., the fats and carbohydrates. 

 We have shown that with fats the muscles are able to perform their work 

 just as well as with carbohydrates. On the other hand, we know of 

 experiments which prove beyond question that carbohydrates can replace 

 fats; in fact, according to the Law of Isodynamics. If all nourishment 

 is withheld from an animal, it will draw on its own body, not only attack- 

 ing its own protein, but especially the fat deposits. If we substitute for 

 the fat which would be used up in this way during starvation the same 

 quantity of fat in food, we find that a complete replacement follows; 

 i.e., the animal does not touch its fat reserves. The same effect can be 

 obtained by substituting for the fat an isodynamic amount of carbohy- 

 drate. This is shown" by the following table, which gives a summary of 

 some of Atwater's experiments. 



The loss of body fat was at one time greater with a carbohydrate diet, 



E. Landergren: Skand. Arch. Physiol. 14, 112 (1903). 



