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

Abstract

BackgroundProtein 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.

Report of a member-led meeting: how stable isotope techniques can enhance human nutrition research

“…Intrinsic labelling using free amino acids in the diet can label chicken and egg. These animal-source proteins showed high digestibility, which compared well with literature values in animals and with intubation or faecal digestibility measurements in human subjects (27) . Subsequently, the negative effect of some dietary components on protein digestion, in this case black tea polyphenols, was demonstrated (28) .…”

Blood 15N:13C Enrichment Ratios Are Proportional to the Ingested Quantity of Protein with the Dual-Tracer Approach for Determining Amino Acid Bioavailability in Humans

“…This approach was shown to be a minimal invasive technique to measure dietary AA digestibility in adults, children, and cystic fibrosis patients ( 6 , 10 , 13 ). This dual-tracer approach was applied using 2 H-labeled test protein in combination with 13 C-labeled standard spirulina ( 8 , 9 , 11 ) as well as with 15 N-labeled spirulina protein in combination with 2 H-labeled phenylalanine ( 6 ). In this context, the present study evaluated the potential of using 15 N-labeling of milk protein with 13 C spirulina for measuring dietary protein AA bioavailability in humans.…”

“…This dual stable isotope tracer method has been applied for measuring the bioavailability of AAs from different intrinsically labeled proteins in humans ( 8 , 9 ). The method relies on the ingestion of a meal containing a test protein of unknown AA bioavailability, intrinsically labeled with 2 H or 15 N, together with a tracer dose of a 13 C-labeled protein or standard free AA mixture of known AA bioavailability.…”

“…Even though the dual-tracer method has been applied in several studies ( 6 , 8 , 10 ) and its results were comparable with bibliographic true ileal or apparent fecal digestibility values in pigs and humans ( 9 , 11 ), the approach has not been validated. The approach is based on several assumptions.…”

Nutritional Strategies to Offset Disuse-Induced Skeletal Muscle Atrophy and Anabolic Resistance in Older Adults: From Whole-Foods to Isolated Ingredients

“…The “food-first” (or “whole-food”) approach, unlike isolated protein components (e.g., whey protein and casein protein, discussed below), contain a variety of other non-protein derived nutrients that may facilitate intramuscular anabolic signalling, MPS and tissue remodelling [ 47 ]. This approach has gained interest in human metabolic research where, compared with studies using isolated proteins, several recent investigations have focused on the muscle anabolic response following consumption of protein-rich whole-foods, such as beef [ 48 , 49 , 50 ], eggs [ 51 , 52 ], skimmed milk [ 50 ], poultry [ 53 , 54 ] and other mixed macronutrient meals [ 55 , 56 , 57 , 58 ]. However, an in-depth discussion of the food-first approach vs. isolated proteins is beyond the scope of this review and has been discussed elsewhere [ 47 , 59 ].…”