Biochemical and Nutritional Effects of Lysine-Reinforced Diets

Abstract

Studies were initiated to determine whether or not the nutritive value of milk could be improved by lysine supplements. Fifteen infants (1–27 months) were studied for periods ranging from 9 to 21 weeks. These children were fed standard fresh or evaporated milk formulae with supplementary foods in accord with prevailing pediatric practice. The vitamin and mineral content of the diet was as high as, or higher than, the recommended levels. The lysine-supplemented diet periods were from 3–4 weeks’ duration and were preceded and followed by control periods of equal duration. The supplement was given as l-lysine, HCl at the rate of 100 mg. of lysine/Kg./day. The biochemical effects of the lysine supplements were determined in terms of anthropometric and body weight changes, nitrogen balance, hemoglobin, total plasma protein, and blood lysine levels. Comparable and parallel measurements were done on 9 infants (2–18 months) who received no lysine supplement during observation periods which ranged from 3–20 weeks. The results of our studies showed that the body weight and nitrogen balances of 5 of the 15 infants were markedly improved by the lysine supplement. Six of the children showed no spectacular weight gains, but urinalyses showed that more nitrogen was retained than before the lysine was added, indicating that these children gained in strength and sturdiness. Blood protein levels also increased during this period. The remaining 4 infants showed no observable improvement when lysine was added to their diet, indicating that lysine-fortified diets are only effective with children who are not getting adequate nourishment from their food. The growth rate of these 4 infants was already well above average. The results of these studies bear the implication that the nutritional value of many infant foods, including cow’s milk, can be substantially improved by small additions of lysine.