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The Gaseous Exchange of the Human Subject

III. As Affected by Small Quantities of Levulose

(From the Nutrition Laboratory of the Carnegie Institution of Washington, Boston, Mass.)

The respiratory exchange of a human subject was determined while the was in the post-absorptive condition and during 3 to 4 hours after the ingestion of levulose in amounts from 5 to 104 grams, which were taken in water at 37°C.

The maximum respiratory quotient was found mostly during the second half hour after levulose, and, with the larger quantities, the increases in the quotients were larger and continued later than with the smaller quantities.

The increase in apparent catabolism of carbohydrate represented 30 to 34 per cent of the amount of levulose given the subject, with the exception of 14 per cent in the experiments with 5 grams of levulose and 53 per cent in the experiments with 15.5 grams. Although the values, 29 and 31 per cent, were found for 52 and 104 grams, not all possible increases are included as the experiments were too short in duration.

Increases in heat production were found in all groups, which varied from 0.5 calorie in 1 hour after 5 grams of levulose to 46 calories in 4 hours after 104 grams. The minimum increase in proportion to the amount given was 1.5 calories in 2 hours after 21 grams.

The specific dynamic action varied from 2 per cent with 21 grams of levulose to 12 per cent with 104 grams, although in the latter case the total heat increment was not measured.

Although the values obtained for carbohydrate after levulose are treated mathematically as increases in metabolism of carbohydrate, a discussion is given with respect to the significance of the changes in the respiratory quotient, and the probability is favored that the reaction after levulose is one of conversion of carbohydrate into an oxygen-poor substance (fat), even when the respiratory quotient does not rise above unity.