A Growth Response of Rats to Glutamic Acid when Fed an Amino Acid Diet

A purified diet containing an amino acid mixture patterned after wheat gluten and supplemented with histidine, lysine, methionine, threonine and tryptophan provided an unusually high rate of gain in rats. When the nonessential amino acids (except cystine and tyrosine) were eliminated from the diet, either singly or in certain combinations, it was found that the omission of glutamic acid in each instance resulted in a greatly reduced growth rate. The omission of other nonessential amino acids had no such effect. Progressively greater weight gains were obtained when increments of glutamic acid were added to a glutamic acid-free diet. The glutamic acid-free diet permitted a gain of only 14.9 gm/week. Maximum growth rate (34.9 gm/week) was obtained with the 5.66% level of glutamic acid. These findings are contrasted with the results of others which did not show glutamic acid to be superior to other sources of nonspecific nitrogen in synthetic amino acid diets.