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

Lusk, Graham, 1866-1932.

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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protein. The possible sources are two in number—carbohydrates and fats. In starvation no carbohydrates are ingested and their supply in the form of reserve glycogen is usually counted as being negligible in such experiments as these. The only other source from which the 169.95 grams of extra carbon could have been derived is fat, and as fat contains 76.52 per cent, of carbon, a destruction of 222.1 grams of fat may be calculated. This fasting man therefore destroyed: Protein 70.81 grams. Fat 222.1 “ That such metabolism actually did take place was further indicated by the comparison of the amount of oxygen needed for the destruction of the above constituents, and the amount of oxygen absorption as determined by the experiment. From the constituents of the protein and fat destroyed, Petten- kofer and Voit deducted the constituents of the urine, which contains part of the C and H belonging to protein. The balance of the carbon and hydrogen was fit for oxidation to carbon dioxid and water. Their calculation may thus be presented: Composition of the protein burned Composition of fat burned Weight in Grams C H 0 ••• 37*i6 5.8 17.1 .... 169.95 25.7 25.1 Total C, H, and 0 metabolized Deduct quantity in the urine .. . . 207.11 8.2 3i-5 2.0 42.2 7.6 Balance available for respiratory CO2 and H20 Oxygen required ,... 198.9 . ... 530.4 29-5 235-7 34-6 Total 0 required for the formation of C02 and H20 Less 0 in the protein and fat Oxygen actually required Oxygen absorption as determined • 73i-5 • 779-9 Difference We may reach the same result by using the most modern figures for the oxygen requirement in the metabolism of the food-stuffs. We now know that to burn 100 grams of meat protein requires 133.43 grams of oxygen, and to burn 100 grams of fat requires 288.5 grams,