Effect on Nitrogen Balance of Adult Man of Varying Source of Nitrogen and Level of Calorie Intake

Abstract

Six young men were fed semipurified diets containing 6.28 g of total nitrogen per day of which 5.50 g was furnished by the nitrogen source under investigation. Nitrogen balance was not significantly different when intact casein was fed than when 18 crystalline essential and nonessential L-amino acids simulating casein were fed. Nonessential amino acids, however, supplied by intact casein or by crystalline L-amino acids patterned as in casein, were superior to nonessential nitrogen supplied by glycine and diammonium citrate or by glycine, diammonium citrate and glutamic acid. Glycine, diammonium citrate and glutamic acid were no better as sources of nonessential nitrogen than glycine and diammonium citrate. Although no significant difference was obtained between the periods in which intact casein and the mixture of 18 essential and nonessential amino acids were given, raising the calorie intake by 500 kcal/day increased nitrogen retention from both sources.