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Comparison of Urea and Diammonium Citrate as Sources of Nonspecific Nitrogen for Human Adults¹

Department of Food and Nutrition, College of Home Economics and Nebraska Agricultural Station, University of Nebraska, Lincoln, Nebraska, 68503

Nonspecific nitrogen may be defined as nitrogen from any metabolically useable, nontoxic source. The objective of the current project was to compare the effectiveness of urea and diammonium citrate as sources of nonspecific nitrogen for human adults. In both studies composing the project, essential amino acids were supplied by a mixture of purified crystalline L-form essential amino acids formulated according to the Rose minimal requirement pattern. In the first study, mean nitrogen balances of subjects receiving 1.77 g N supplements from urea + glycine or diammonium citrate (DAC) + glycine were –1.65 g and – 1.12 g, respectively. When the two supplements were raised to supply 4.77 g N, mean N balances were –0.85 g (urea + glycine) or –0.52 g (DAC + glycine). At the 7.77 g N supplementation level, mean N balances were +0.12 (urea + glycine) and +0.28 (DAC + glycine) and at the 10.77 g N supplementation level mean values were +0.74 (urea + glycine) and +0.72 (DAC + glycine), respectively. In the second study, mean nitrogen balances of subjects receiving supplements of 4.2 g N from urea or DAC were –0.42 g and –0.24 g N, respectively. Results suggest that urea is a less efficient source of nonspecific nitrogen than DAC, but that this difference can only be demonstrated when total nitrogen intake is less than optimal.

KEY WORDS: • nonspecific nitrogen • urea • diammonium citrate • amino acids • proteins

¹ Published with the approval of the Director as Paper no. 3442, Journal Series, Nebraska Agricultural Experiment Station. Funds for support of this project were provided by the Nebraska Agricultural Experiment Station, Project no. 91-7.

Manuscript received 21 August 1972.