INGESTION OF CARBOHYDRATES. 171 



INGESTION OF CARBOHYDRATES. 



In the historical development of the study on the influence of food 

 upon the metabolism the first observations in which demonstrable 

 increases could be determined were those with protein. These in- 

 creases were so large that it was not at all strange that observers 

 expected to find a considerable rise in the metabolism with both fat 

 and carbohydrates. Accordingly, when a much smaller increment in 

 the metabolism was found with carbohydrates than that obtained in 

 experiments with protein, the influence of the former class of nutrients 

 was without doubt given less consideration than it should have been. 



The actual importance of the increases with carbohydrates may have 

 been obscured by several causes. First, the effect of carbohydrate 

 ingestion persists for a much shorter time than that following the inges- 

 tion of protein; hence, in the experimental period first used (24 hours) 

 the increase in the metabolism in the hours immediately following the 

 taking of the carbohydrate food may have disappeared when the values 

 for the essentially basal metabolism in the later hours of the day were 

 included; in other words, the "peak" effect of the carbohydrate inges- 

 tion was lost as a result of the lengthening of the experimental period. 



Secondly, it has frequently happened that the basal value was deter- 

 mined in 24 hours, or even longer, of complete starvation. Experi- 

 ments have shown 1 that during a period of this length without food 

 there is a very considerable draft upon the carbohydrate storage in the 

 body; consequently when carbohydrate is afterwards ingested, the 

 body attempts first to replenish the store of this material. The effect 

 on the metabolism due to the ingestion of food is thus considerably less- 

 ened by the fact that the carbohydrate is in large part not burned, but 

 simply stored as glycogen. 



In Rubner's experiment on man 2 (and in this monograph we are 

 dealing entirely with experiments on man) a series of experiments on 

 5 consecutive days was carried out. On the first day the subject fasted 

 and did no work ; on the second day he was given protein without work ; 

 on the third day protein with work; on the fourth day sugar without 

 work ; and on the fifth day sugar with work. Considering specifically 

 the fourth day, when sugar was given without work, we find that the 

 heat output per 24 hours was 2,023 calories as compared with a basal 

 value of 1,976 calories, an increment of only 47 calories. A close exam- 

 ination of the experimental procedure shows that the 3 days prior to 

 the sugar day, i. e., a day of hunger, a day with protein, and a day with 

 protein and work, all contributed toward the depletion of the glycogen 

 supply in the body, and it is not surprising that no larger increment in 

 the metabolism was found. 



'Johansson, Skand. Arch. f. Physiol., 1909, 21, p. 1. See, also, p. 70 of this monograph. 

 'Rubner, Sitzber. K. Preuss. Akad. Wiss., 1910, p. 316. 



