Between- and within-person variability in postprandial blood amino acid kinetics after ingestion of a good and a moderately digestible protein source: a randomised trial.

Abstract

Protein intake and the resulting postprandial aminoacidemia are important anabolic stimuli. However, considerable individual variation in postprandial amino acid (AA) kinetics can be expected. In this study, the aim was to quantify the variability in postprandial AA kinetics within and between individuals after consumption of a moderately digestible plant protein concentrate (lucerne (alfalfa), LPC) and an easily digestible animal protein concentrate (whey, WPC). Eighteen healthy young adults consumed a 20 g protein drink on five occasions (3xLPC; 2xWPC). Plasma AA kinetics were calculated, and a mixed model was fitted to describe within- and between-individual variability and to calculate the intra-class correlation coefficient (ICC). AA kinetics showed significant variation between and within individuals, both for WPC and LPC. Between-individual variation in postprandial response for total AA (TAA) or total essential AA (TEAA) was in general larger than within-individual variation for WPC with the ICC with or without blood volume (BV) correction ranging from 0·45 to 0·77. For LPC, the within-individual variation of the TAA response was higher than the between-individual variation, and for TEAA they were more or less equal, with the ICC with or without BV correction ranging from 0·34 to 0·58 for LPC. Subjects with a high level of aminoacidemia for one protein source were not necessarily those with a high level for the other protein source. Our results indicate that between- and within-person variation in postprandial AA kinetics are substantial and should not be neglected.