A COMPARISON OF THE EFFECTS ON THE HUMAN RESPIRATORY EXCHANGE OF HEXOSES INGESTED SEPARATELY AND TOGETHER

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Abstract
With the helmet open-circuit apparatus a study was made of the respiratory exchange of an adult man before and after ingestion of 20 gm. each of glucose, fructose, and galactose and after various combinations of 2 sugars in 20-gm. amts., each, during 1 hr. previous to ingestion and for 21/2 hrs. after ingestion, in 15-min. periods. Glucose and fructose together, galactose and fructose, and galactose and glucose, produced nearly the same rise in R.Q. as the summation of the rises with the sugars given separately. Slightly smaller rises were caused by 40 gm. of lactose than the equivalent 20 gm. of glucose and 20 gm. of galactose given together, but the return to the preingestion values in the R.Q. was not so rapid with lactose. When glucose and fructose were given together, the increase in carbohydrate combustion averaged 9.2 gm. as compared with 8.3, the sum of the increases when given separately. Galactose and fructose together produced 11.3 gm. increase as compared with 10.8 separately; galactose and glucose together 9.2 gm. as compared with 6.1 separately, and the equivalent in lactose, 9.3 gm. All the results as to increased R.Q. and combustion were more uniform than for increased heat production. When 20 gm. each of glucose and fructose were given together, the increased heat production (2.4 cal.) was equal to the summation of the two given separately. However, the effect of 20 gm. each of fructose and galactose together was 6.8 cal. as compared with 2.1 when summated, and of galactose and glucose together, 8 as compared with 1.5. The qualitative reactions due to the ingestion of hexoses were thus the same whether given separately or together, but some other factor than the transformations of the carbohydrates played a role in bringing about the increases in heat production when galactose was ingested with some other sugar. The cause may be the presence of more unabsorbed galactose in the alimentary tract when other sugars are ingested, or the greater formation of lactic acid in the intermediary metabolism of galactose, or the smaller formation of glycogen when other glycogen formers are available.

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