Availability to Man of Amino Acids from Foods

Abstract
Two studies were conducted to determine the availability to human subjects of threonine in corn. The only difference in the diets between the two studies was that one contained 10 gm of nitrogen daily and the other, 6 gm. Availability was determined by feeding in alternate experimental periods equivalent amounts of purified threonine and corn threonine and comparing the resultant nitrogen balance. In both studies threonine in corn was completely available to man. The mean nitrogen balance of the subjects consuming the diet containing 10 gm of nitrogen and 620 mg of threonine was slightly positive, but that of subjects receiving 6 gm of nitrogen and 620 mg of threonine was distinctly negative. Failure to achieve nitrogen equilibrium with the lower nitrogen intake may be attributed to an insufficiency of nitrogen and/or calories. The threonine requirement for young women appears to exceed 280 mg per day.