The Specific Dynamic Effects of ProteinFatand Carbohydrate as Determined with the Albino Rat at Different Planes of Nutrition

Abstract

The average specific dynamic effects resulting from the additionto a basal maintenance rationof caseinstarch and olive oilrespectivelyexpressed as percentages of the metabolizable energy of these supplementswere 31.4 per cent for casein22.5 per cent for starch and 16.5 per cent for olive oil. These values were considerably greater than the corresponding increases in heat productionover the fasting metabolismresulting from the exclusive feeding of caseinstarch and olive oilwhen these heat increments were related to the metabolizable energy ingested. As a contribution to the establishment of the causes of these differences in heat increment values determinations were madeat the different planes of nutritionof the percentages of the total heat derived from proteinfat and carbohydrateand of the sparing of body nutrientsunder the different dietary treatments. Attempts were made to confirm the existence of specific dynamic effects of body protein and fat katabolized by accounting for the sparing effects of starcholive oil and caseinon the katabolism of body tissue. All heat increment values determined with respect to fastingwith correction for the sparing of body proteinwere found to be considerably higher than the corresponding uncorrected values. The heat increment values of caseinstarch and olive oilcorrected for the sparing of both body protein and fatwere found to agree reasonably well with the heat increment values of these substances determined above maintenance—with the heat production of energy and nitrogen equilibrium as a base value. These conditions (of determination above maintenance) are believed to be as nearly correct as practicable for measuring the specific dynamic effect of any nutrient. The results obtained constitute fairly satisfactory confirmation of the conclusion of Rubner that the heat produced by the katabolism of body protein includes a factor of waste heat of utilization; and also justify the conclusion of ForbesBraman and Kriss that heat increment values of rations determined directly with reference to the fasting heat production (uncorrected for the sparing of body tissue) are lower than the true energy expense of utilization by the amounts of the dynamic effect of body substance spared.