THE CARBOHYDKATES AND THEIR METABOLISM 271 



The Functions of Carbohydrate in the Diet. The paramount func- 

 tion of carbohydrate in the diet is to yield energy to the cells in the process 

 of its oxidation. It burns in the body apparently with greater ease than 

 does protein or fat, hence it may be considered as having a sparing influ- 

 ence on both. With regard to protein its influence is more specific, for 

 the intermediary products of carbohydrate metabolism, lactic acid and 

 pyruvic acid have been shown to have the power of uniting with ammonia 

 in the liver and giving rise to alanin. This conserves nitrogen for the 

 body, which would ordinarily have been excreted, Knoop (1910), Emb- 

 den (1910), and Schmitz (1910). For further discussion of the influ- 

 ence of carbohydrate on protein metabolism see the chapter on Protein 

 Metabolism, page 118. 



Influence of Carbohydrate on Intermediary Metabolism of Fat. An- 

 tiketogenesis. Ordinarily when fat burns in the body it is completely 

 oxidized to carbon dioxid and water. Under certain conditions, however, 

 the oxidation is not- complete. In cases of absolute starvation "acetone 

 bodies" (|3-hydroxybutyrie acid, aceto-acetic acid, and acetone) appear in 

 the urine, the last because of its extreme volatility is also excreted 

 through the breath. If an individual is kept on a diet of protein and fat 

 without any carbohydrate, these bodies will also appear in the urine. In 

 severe diabetes where the combustion of carbohydrates is completely lost, 

 the amount of acetone bodies formed may be enormous, over one hundred 

 grams a day. Because the aceto-acetic acid and the acetone have the car- 



nonyl (CO) radical, they are known as ketones and their formation in 



the body is called ketogenesis. All the acetone bodies originate from the 

 catabolism of fat and from certain of the amino acids of protein metabo- 

 lism. 



Because it was recognized that whenever carbohydrates burn in the 

 body ketogenesis stops and that no ketogenesis occurs as long as the body 

 is capable of oxidizing glucose, antiketogenetic properties were attributed 

 to glucose. 



In normal fasting individuals who develop kctonuria, certain sub- 

 stances like glycerol, glycocoll, alanin, and aspartic acid have proven to 

 be antiketogenetic. In diabetic individuals, however, they are without 

 effect, because they are completely converted to glucose and excreted as 

 such. Alcohol has proven to be a marked antiketogenetic substance. ((). 

 Xeubauer (1906), Benedict and Torok (1906).) 



In 1913 Ringer and Frankel performed a series of experiments on 

 diabetic dogs who developed considerable ketonuria. After adminis- 

 tering acetaldehyde to these dogs they found a very marked antiketogenetic 

 effect. At the same time they also obtained an increase in the glucose 

 elimination. They suggested the idea that it was possible that acetalde- 



