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. 2021 Jan;68(1):32-36.
doi: 10.3164/jcbn.20-79. Epub 2020 Jul 31.

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

Kohsuke Hayamizu  1 , Yuma Aoki  1 , Nobuo Izumo  1 , Makoto Nakano  1
Affiliations

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

Kohsuke Hayamizu et al. J Clin Biochem Nutr. 2021 Jan.

Abstract

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.

Keywords: break-point; change-point regression model; indicator amino acid oxidation; inter-individual variability; protein requirement.

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Conflict of interest statement

No potential conflicts of interest were disclosed.

Figures

Fig. 1
Fig. 1
The oxidation pattern of amino acids in studies using the indicator amino acid oxidation (IAAO) method. The lines represent kinetic responses to graded intakes of the test amino acid. The change-point in the oxidation response has been proposed as the physiological requirement of the test amino acid for the average individual in a population.
Fig. 2
Fig. 2
An example IAAO profile by CPRM. Bold black line indicates the IAAO profile of overall subjects. Gray lines indicate individual IAAO profiles. (A) Elango,(7) (B) Bandegan,(9) (C) Rafii.(12)
See this image and copyright information in PMC

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