Abstract
ABSTRACTBackgroundProtein quality assessment through the Digestible Indispensable Amino Acid Score requires accurate measurements of true ileal protein and amino acid digestibility, for which a dual isotope technique was recently developed. However, the ileal digestibility of indispensable amino acids (IAA) in humans from high-quality proteins is not well known.ObjectiveThe aim of this study was to intrinsically label hen's egg and meat protein by the use of uniformly 2H-labeled amino acids, and to measure their true ileal indispensable amino acid (IAA) digestibility via the dual isotope method in humans.Design 2H-labeled lyophilized boiled egg white protein, whole boiled egg, and cooked meat were obtained from layer hens (BV-300) administered a uniformly 2H-labeled amino acid mix orally for 35 d with their daily feed. The ileal IAA digestibility of these proteins was determined with reference to digestibility of previously characterized [U-13C]spirulina in a dual tracer method in healthy Indian subjects whose intestinal health was measured by the plasma kynurenine-to-tryptophan (KT) ratio.ResultsAll subjects had normal KT ratios. The mean ± SD true ileal IAA digestibility of 2H-labeled egg white protein, whole boiled egg, and cooked meat was 86.3% ± 4.6%, 89.4% ± 4.5%, and 92.0% ± 2.8%, respectively. Leucine digestibility correlated with the KT ratio (r = −0.772; P = 0.009).ConclusionsUniformly 2H-labeled hen's egg and meat protein can be used to measure ileal IAA digestibility by the dual isotope tracer approach in humans. The mean IAA digestibility values for these high-quality proteins in the healthy Indians studied were similar to values obtained in earlier human and animal experiments. Leucine digestibility in these meal matrices correlated with the KT ratio, but this aspect needs further evaluation. This trial was registered at the Clinical Trials Registry of India (http://ctri.nic.in) as CTRI/2018/03/012265.
Highlights
Recent recommendations have emphasized the importance of dietary protein quality and the need for its assessment by use of the Digestible Indispensable Amino Acid Score, necessitating true ileal digestibility measurements on individual indispensable amino acids (IAAs) with respect to a nutritional reference, such as milk or egg white protein [1]
The IAA enrichment of egg white tracer of the initial parts of the pilot study with the 6 mg tracer dose and the 12-mg IAA tracer dose is shown in Supplemental Figure 2
The reported apparent fecal amino acid and fecal nitrogen digestibility values in the literature ranged from 90% to 97% [15, 22, 23], and were similar to values found in the present study
Summary
Recent recommendations have emphasized the importance of dietary protein quality and the need for its assessment by use of the Digestible Indispensable Amino Acid Score, necessitating true ileal digestibility measurements on individual indispensable amino acids (IAAs) with respect to a nutritional reference, such as milk or egg white protein [1]. A dual isotope method for measuring the human ileal digestibility of different IAAs in intrinsically labeled protein was proposed [4], in which the measurement of absorbed amino acids from a 2H intrinsically labeled test protein could be compared against that for a 13C intrinsically labeled standard protein with known digestibility It is suited for measurements in vulnerable age groups and the study of varying physiological states. The mean IAA digestibility values for these high-quality proteins in the healthy Indians studied were similar to values obtained in earlier human and animal experiments Leucine digestibility in these meal matrices correlated with the KT ratio, but this aspect needs further evaluation.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
