The Specific Dynamic Effects of Amino Acids and Their Bearing on the Causes of Specific Dynamic Effects of Proteins

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Abstract
The specific dynamic effects of glutamic acid, glycine, alanine, tyrosine, aspartic acid and asparagine were determined by feeding these amino acids to rats in considerable quantities (some equicaloric) as supplements to a basal maintenance ration. The increases in heat production due to the supplements were measured with respect to the heat production of maintenance as a base value. All amino acids showed positive dynamic effects. The results were expressed in ten different ways, and a study was made of the relationships between the heat increments and the various metabolic factors. The heat increments expressed in relation to ingested or urinary nitrogen, as well as the values expressed per millimol of amino acid metabolized, were found to be highly variable, and showed no direct correlation between the specific dynamic effects of amino acids and nitrogen metabolism. The results expressed as Calories per gram of carbon of the amino acids metabolized were much more uniform than those expressed per gram of extra urinary nitrogen, thus indicating that the metabolism of carbon is probably a more important factor in the production of the specific dynamic effects than is the metabolism of nitrogen. The closest correlation was found between the dynamic effects and the metabolizable energy of the amino acids. The results are consistent with the theory that dynamic effects of amino acids, and therefore of proteins, are byproducts of intermediary chemical reactions (oxidative and synthetic) and energy changes, and they do not lend support to the idea that certain amino acids or certain of their cleavage products act in the body as special metabolic stimulants in the pharmacodynamic sense.