Ileal digestibility of intrinsically labeled hen's egg and meat protein determined with the dual stable isotope tracer method in Indian adults

• Published in: The American journal of clinical nutrition Vol. 108; no. 5; pp. 980 - 987
• Main Authors: Kashyap, Sindhu, Shivakumar, Nirupama, Varkey, Aneesia, Duraisamy, Rajendran, Thomas, Tinku, Preston, Thomas, Devi, Sarita, Kurpad, Anura V
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.11.2018; Oxford University Press; American Society for Clinical Nutrition, Inc
• Subjects: Adolescent; Adult; Adults; Albumen; Amino acids; Amino Acids - metabolism; animal experimentation; Animal research; Animals; Chickens; Clinical trials; cooked foods; Cooking; Diet; Dietary Proteins - metabolism; Dietary Proteins - standards; Digestibility; Digestible Indispensable Amino Acid Score (DIAAS); Digestion; dual stable isotope tracer method; egg albumen; egg protein; Egg Proteins - metabolism; Eggs; environmental enteric dysfunction; Female; Food Analysis - methods; freeze drying; Humans; ileum; Ileum - metabolism; India; Intestine; intrinsic labeling; isotope labeling; Isotopes; Kynurenine - blood; kynurenine-tryptophan ratio; laying hens; Leucine; Male; Meals; Meat; meat protein; Meat Proteins - metabolism; Medical research; Metabolism; Middle Aged; Original Research Communications; protein value; Proteins; Quality assessment; Quality control; Spirulina; Stable isotopes; Tryptophan; Tryptophan - blood; Young Adult; India; meat protein; egg protein; intrinsic labeling; dual stable isotope tracer method; EED; IAA; LT; KT; IR; ppme; LC-MS/MS; kynurenine-tryptophan ratio; KIR; environmental enteric dysfunction; Digestible Indispensable Amino Acid Score (DIAAS)
• ISSN: 0002-9165; 1938-3207; 1938-3207
• DOI: 10.1093/ajcn/nqy178

Protein 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. The 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. 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. All 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). Uniformly 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.