The Relationship of Carbohydrate Metabolism to Protein Metabolism
IV. The Effect of Substituting Fat for Dietary Carbohydrate
One Figure
W. S. T. Thomson and
H. N. Munro
Department of Biochemistry, University of Glasgow, Scotland
1. When fat is exchanged isocalorically for carbohydrate inthe diet of the rat, urinary nitrogen output increases for afew days and then returns to its former level. The transitorynature of the response may account for the failure of some investigatorsto observe any difference in nitrogen balance between groupsof rats receiving equicaloric diets of differing fat and carbohydratecontent.
2. Exchange of fat for carbohydrate in protein-containingmealsleads to a much greater increase in nitrogen output thanoccursafter a similar exchange in meals devoid of protein.Thus themain consequence of replacing the carbohydrate of amixed dietby fat is a deterioration in the utilization of dietaryprotein.
3. The change in nitrogen balance resulting fromsubstitutionof fat for carbohydrate is of similar magnitude,whether thefat is fed with the protein of the diet or apartfrom it. Thisindicates that the phenomenon is essentially dueto removalof carbohydrate from the protein-containing mealand not toan adverse effect of feeding fat with protein.
4.There is a linear relationship between the amount of carbohydratefed along with the protein of the diet and the nitrogen balanceof the rat.