Estimation of L-lysine Requirement by Indicator Amino Acid Oxidation Method Using Random Effects Model

Abstract

In recent years, it has been suggested that the method for determining the requirements for indispensable (essential) amino acids be changed from the nitrogen balance method to the tracer methods. In particular, the indicator amino acid oxidation (IAAO) method has been implemented. Although the requirements for indispensable amino acids have been reported in several independent trials, no reported study has statistically integrated these data. In addition, the requirement as obtained from the IAAO method reported to date is the estimated average requirement (EAR), which will be met nutrient requirements in 50% of population only; thus, the risk of deficiency cannot be ruled out from a nutritional perspective. In this study, we statistically synthesized the data of multiple required amounts of lysine obtained by the IAAO method and attempted to accurately estimate the EAR. Further, we estimated the recommended dietary allowance (RDA) value from the obtained estimated EAR value. Analysis using a random effects model estimated that the EAR of lysine in healthy adults was approximately 37 mg/kg (95% CI: 31.2–42.5). In addition, the RDA was estimated to be about 46 mg/kg. These values are higher than the previously reported value of 30 mg/kg.