American Journal of Clinical Nutrition, Vol 21, 217-222, Copyright © 1968 by The American Society for Clinical Nutrition, Inc.

Nitrogen Retention of Adults Given Variable Quantities and Proportions of Lysine

¹ From Purdue University Agricultural Experiment Station and School of Home Economics, Department of Foods and Nutrition, Lafayette, Indiana

When young men and women were fed 1.5, 2.0, and 2.5 times the quantities of essential amino acids present in a previously developed basic mixture, with the exception of lysine, which was restricted to two-thirds of these amounts, mean daily retentions of nitrogen were 0.01, 0.30, and 0.56 g, respectively. Regression of nitrogen balance on intake of essential amino acids, = 532 X – 792, was linear. The slope of the line did not differ significantly from that observed earlier when lysine was not restricted, but the elevation was slightly lower. Since retention decreased from 0.56 to 0.09 g when lysine was dropped from 1,500 to 900 mg in the presence of 2.5 times the basic mixture, high levels of other essential amino acids were not used effectively when lysine was restricted.

In the second experiment, 900, 1,800, 2,700, and 3,600 mg of lysine were administered in conjunction with twice the basic mixture of other amino acids. The corresponding daily nitrogen balances were 0.16, 0.84, 0.99, and 1.09 g.