Estimation of inter-individual variability of protein requirement by indicator amino acid oxidation method

• Published in: Journal of Clinical Biochemistry and Nutrition Vol. 68; no. 1; pp. 32 - 36
• Main Authors: Hayamizu, Kohsuke, Aoki, Yuma, Izumo, Nobuo, Nakano, Makoto
• Format: Journal Article
• Language: English
• Published: Japan SOCIETY FOR FREE RADICAL RESEARCH JAPAN 01.01.2021; Japan Science and Technology Agency; the Society for Free Radical Research Japan
• Subjects: Amino acids; break-point; change-point regression model; Coefficient of variation; Diet; indicator amino acid oxidation; inter-individual variability; Invasiveness; Mathematical analysis; Nitrogen balance; Original; Oxidation; protein requirement; Proteins; Regression analysis; Regression models; Variability; Variation; protein requirement; indicator amino acid oxidation; change-point regression model; break-point; inter-individual variability
• ISSN: 0912-0009; 1880-5086
• DOI: 10.3164/jcbn.20-79

The indicator amino acid oxidation (IAAO) method is a recently developed method to determine the protein requirement and is particularly useful for analyzing human subjects because of its minimal invasiveness. IAAO study is performed using two-phase regression analysis, with the break-point between these phases being the estimated average requirement. However, this method requires that the break-point lie within a certain range in advance, which is in practice difficult. Recently, the change-point regression model (CPRM) has been proposed to be more effective for two-phase regression analysis. There is also a need to re-evaluate the value corresponding to the recommended dietary allowance. Calculation of the recommended dietary allowance requires data on the average requirement and the inter-individual variability of this requirement. However, no inter-individual variability values have been reported in the IAAO method. The aim of this study was thus to estimate the inter-individual variation in protein requirement using CPRM. From seven IAAO studies, the inter-individual variability was estimated as a coefficient of variation of about 20%. The coefficient of variation of the protein requirement determined by IAAO study was wider than the ordinary coefficient of variation obtained from the nitrogen balance test.