Nitrogen balance studies with amino acid supplemented low-protein diet in uremia

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Abstract
Apparent nitrogen balance was studied in 14 patients with advanced renal failure and uremic symptoms during treatment with a 20-g protein diet supplemented with varying amounts of a mixture of the essential amino acids and histidine. Total nitrogen intake and urinary loss of nitrogen were determined by analysis. With an assumed mean loss of 2 g N per 24 hr from feces and skin all patients were in negative nitrogen balance on the 20-g protein diet only. The diet was supplemented with the essential amino acids as proposed by Rose and histidine in amounts corresponding to 1.3 and 2.6 g N per 24 hr iv or 1.3 g N per 24 hr orally. The apparent nitrogen balance was considerably improved with all supplementation schedules. Supplementation with 1.3 g N per 24 hr iv, however, could not bring the patients into nitrogen balance taking fecal and dermal nitrogen losses into account, while about half of the patients were judged to be in nitrogen balance on supplementation with 2.6 g N per 24 hr iv or 1.3 g N per 24 hr orally. Apparent nitrogen balance was better when 1.3 g N was given by mouth than iv and the difference between 1.3 g N by mouth and 2.6 g N iv was less than 1.3 g N. This indicates that the essential amino acids were more efficiently utilized when given by mouth. Supplementation of the 20 g diet with 1.3 g N as essential amino acids and histidine by mouth appears to be sufficient for clinical use. Evaluation of results of long-term treatment necessitates other techniques than short-term nitrogen balance studies.