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.
Highlights
Proteins are made up of 20 different L-amino acids linked by peptide bonds
The information on the break point and its 95% confidence interval obtained from the indicator amino acid oxidation (IAAO) method for L-lysine in healthy adult subjects was extracted from the following studies
[6] This study investigated the lysine requirements of five healthy adult males as determined by the IAAO method, in which the oxidation of L-[1-13C] phenylalanine was measured as the indicator amino acid
Summary
Proteins are made up of 20 different L-amino acids linked by peptide bonds. They are important components of organisms, and their types differ depending on the number and types of amino acids, and the sequence of the peptide bonds. In recent years, research using tracers has attracted attention as an alternative [2, 3] This method was used for estimating the amino acid requirements of healthy adults in the “Joint FAO/WHO/UNU expert consultation on protein and amino acid requirements in human nutrition” in 2002 [4,5,6,7,8,9,10,11,12,13]. At the above-mentioned scientific conference, several requirements for L-lysine for healthy adults were presented, as determined using different methods included the nitrogen balance method This requirement was determined to be 30 mg/kg based on the result of the best approach at that time, 24 h indicator amino acid balance (IAAB) studies [4, 11, 12]. No re-evaluation of the results regarding L-lysine requirement obtained by the IAAO method has been performed using a statistical approach (Issue 1)
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