Reevaluation of the protein requirement in young men with the indicator amino acid oxidation technique

Abstract

The indicator amino acid oxidation technique defined a protein requirement that is comparable with that estimated by the application of a biphase linear regression model to nitrogen balance data in the literature. Our data and the reanalysis of the preexisting nitrogen balance data suggest that the current recommended protein requirements are too low and require reassessment.

Recent developments in understanding protein needs – How much and what kind should we eat?

“…Concern has been raised that this experimental design used a complete and balanced mixture of amino acids, instead of intact protein; and hourly meals, instead of standard meals every 4 h. An Asian group (Tian et al 2011) has conducted studies in young Chinese women using intact protein and meal feeding and applied the IAAO method to determine protein requirement. The results obtained for mean and population safe protein requirement of 0.91 and 1.09 g/(kg·day) are comparable to the estimates obtained by Humayun et al (2007). Once it is appreciated that the dietary function of protein is to provide the 20 amino acids for which tRNA exists (Institute of Medicine 2005), the observation of Tian et al (2011) are not surprising.…”

“…The World Health Organization Committees estimated mean protein requirements as 0.66 g/(kg·day) with a population requirement of 0.8 g/(kg·day), based on nitrogen balance data analyzed using mono-linear regression. A reanalysis of the published nitrogen balance data using 2-phased linear crossover analysis resulted in a mean requirement of 0.91 g/(kg·day) and a population estimate of 1.0 g/(kg·day), which are identical to that of Voit 100 years earlier (Humayun et al 2007). This estimate was confirmed using the carbon oxidation based method, IAAO, with a mean estimate of 0.93 g/(kg·day), which is essentially the same as the reanalysis of the nitrogen balance data (Humayun et al 2007).…”

“…A reanalysis of the published nitrogen balance data using 2-phased linear crossover analysis resulted in a mean requirement of 0.91 g/(kg·day) and a population estimate of 1.0 g/(kg·day), which are identical to that of Voit 100 years earlier (Humayun et al 2007). This estimate was confirmed using the carbon oxidation based method, IAAO, with a mean estimate of 0.93 g/(kg·day), which is essentially the same as the reanalysis of the nitrogen balance data (Humayun et al 2007). Concern has been raised that this experimental design used a complete and balanced mixture of amino acids, instead of intact protein; and hourly meals, instead of standard meals every 4 h. An Asian group (Tian et al 2011) has conducted studies in young Chinese women using intact protein and meal feeding and applied the IAAO method to determine protein requirement.…”

An Evaluation of Protein Intake for Metabolic Demands and the Quality of Dietary Protein in Rats Using an Indicator Amino Acid Oxidation Method

“…Humayun et al (19) reevaluated the protein requirement in young men employing the IAAO method, and the protein source of the experimental diet was consumed hourly in small meals consisting of a crystalline amino acid mixture. In the present study, casein and wheat gluten were employed as the protein source, and therefore, as the rats consumed the experimental diet at 3-h intervals, it can be considered that the mechanism of assimilation differed from that of the amino acid mixture.…”

“…In 2007, Humayun et al ( 19 ) applied the IAAO method and conducted a reevaluation study on the protein requirements in healthy young men by feeding the subjects graded protein intake as a crystalline amino acid mixture and measuring changes in the oxidation of orally administered L - [1][2][3][4][5][6][7][8][9][10][11][12][13] C]phenylalanine. However, no studies have previously been conducted on determining the protein requirement using protein itself in animals or humans employing the IAAO method.…”