The elements of the science of nutrition / by Graham Lusk.

  • Graham Lusk
Date:
1917
Catalogue details

Licence: In copyright

Credit: The elements of the science of nutrition / by Graham Lusk. Source: Wellcome Collection.

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    or “repeated fast” was then initiated which lasted 104 days with no harmful results. The day to day history of the starving organism must now be considered. INFLUENCES AFFECTING PROTEIN METABOLISM In the first days the amount of protein metabolized depends upon the two factors, the glycogen content of the individual and the quantity of protein ingested before the starvation period. The influence of the first factor was shown by Prausnitz.1 Fifteen individ- uals (mostly medical students who were taking a course of instruc- tion in the laboratory) fasted for sixty hours. The first day’s urine was collected beginning after twelve hours of fasting. The second day’s urine contained in 12 cases more nitrogen than that of the first day of starvation. The lower protein destruction on the first starvation day must have been due to the continued use of sugar from the glycogen supply. It is known that the combustion of sugar considerably reduces the protein metabolism, so the second day and not the first of starvation should be taken as the basis of the fasting protein metabolism. This influence of glycogen metabolism on that of protein during the first and second days of fasting is beautifully shown in experi- ments by Benedict2 (see also p. 98). INFLUENCE OF GLYCOGEN METABOLISM ON THAT OF PROTEIN IN FASTING. WEIGHTS IN GRAMS Individual First Day Second Day Glycogen Metabolized N Elimi- nated Glycogen Metabolized N Elimi- nated Total Per Kg. Total Per Kg. S. A. B 181.6 3-15 5-84 29.7 0.52 11.04 S. A. B 135-3 2.31 10.29 18.1 0.31 11.97 S. A. B 64.9 1.09 12.24 23.1 o-39 12-45 H. C. K 165.6 2-33 9-39 44-7 0.64 14.36 H. R. D 32.8 o-59 13-25 41.6 0.76 13-53 It is evident that where there is an abundant glycogen reserve the protein metabolism is reduced by the oxidation of carbohydrates, but where there is little glycogen to draw upon the protein metabo- lism is high even on the first day of starvation. 1 Prausnitz, W.: Z. f. Biol., 1892, 29, 151. . . 2 Benedict, F. G.: “The Influence of Inanition on Metabolism, Carnegie Insti- tution of Washington, Bull. 77, 1907.