Cereal Chem 49:223 - 231.  |  VIEW ARTICLE
Interrelationships of Leucine with Lysine, Tryptophan, and Niacin As They Influence Protein Value of Cereal Grains for Humans.

C. Kies and H. M. Fox. Copyright 1972 by the American Association of Cereal Chemists, Inc. 

The most striking difference between the typical amino acid proportionality pattern of wheat and corn grains is the high leucine content of corn. A series of three studies has been completed on possible leucine interactions with nutrients supplied by these cereals in low amounts in proportion to human needs or for which availability is questioned. In all three studies, adult human subjects were fed diets containing 4.0 g. nitrogen (N) per day from whole-ground wheat grain or whole-ground wheat grain plus L-leucine to total the level commonly found in corn grain. The specific objectives were to compare the effectiveness on protein nutriture of supplementation (with lysine, tryptophan, and niacin) of wheat diets containing high and normal amounts of leucine. Mean N balances (grams per day, respectively) were: of the eight subjects fed wheat alone, wheat plus lysine, wheat plus leucine, or wheat plus leucine and lysine, -0.66, -0.12, -1.08, and -0.69; of the nine subjects fed wheat alone, wheat plus tryptophan, wheat plus leucine, or wheat plus leucine and tryptophan, -0.90, -1.00, -1.19, and -1.39; of the ten subjects fed wheat alone, wheat plus niacin, wheat plus leucine, or wheat plus leucine and niacin, -0.95, -0.87, -1.20, and -0.92. These results suggest that high- level leucine content of corn is an important factor in the relatively poorer nutritional performance of corn grain, in comparison to wheat grain, in human feeding trials. Lysine supplementation of wheat was shown to be effective regardless of leucine content, although the amount of lysine added was not completely able to overcome the adverse effect of the increased amount of leucine. Niacin supplementation was effective only at high leucine-intake levels. Tryptophan supplementation was ineffective or had a slight negative effect at both levels of leucine intake.