True ileal digestibility of legumes determined by dual-isotope tracer method in Indian adults

Abstract

Background Good-quality plant protein sources are important for protein adequacy in a balanced diet. Legumes are known to be a source of good quality plant protein, but the true ileal digestibility of indispensable amino acids (IAAs) of commonly consumed legumes is not known in humans. Objectives In this study we measured the true ileal IAA digestibility of 2H-intrinsically labeled chickpea, yellow pea, and mung bean (hulled and dehulled) protein, using the dual-isotope tracer technique referenced to a standard protein ([U-13C] spirulina). The study also aimed to validate the use of [U-13C] spirulina as a reference protein in this method. Methods 2H-intrinsically labeled legumes, obtained by watering plants with deuterium oxide (2H2O), were administered in a plateau feeding method to healthy Indian adults to measure their true ileal IAA digestibility with the dual-isotope tracer technique, using [U-13C] spirulina protein or a 13C-algal IAA mixture as the standard. Result The true ileal IAA digestibilities (mean ± SD) of chickpea, yellow pea, and mung bean were 74.6 ± 0.8%, 71.6 ± 1.3%, and 63.2 ± 1.5%, respectively. The true mean ileal IAA digestibility of mung bean when referenced to [U-13C] spirulina protein or a 13C-algal IAA mixture did not differ significantly (63.2 ± 1.5% versus 64.0 ± 2.4%, P > 0.05). The true ileal IAA digestibility of mung bean improved to 70.9 ± 2.1% after dehulling. Conclusions The true mean ileal IAA digestibility of legumes in healthy Indian adults was lower than expected. Traditional processing techniques such as dehulling improve protein digestibility by about 8%. This study was registered in the Clinical Trials Registry of India (CTRI): CTRI/2017/11/010468 (http://ctri.nic.in, accessed on 28/03/2019).

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

“…In previous dual-tracer studies, similar protein quantities (21–24 g vs 18.2 g in the present study for the low-protein meal) were provided in a meal with higher energy content (714–834 kcal vs this study's meal of 513 kcal) ( 9 , 11 ). Therefore, our study's protein-to-energy ratio was only slightly higher for the low-protein meal (14.3 E% protein) but markedly higher for the present high-protein meal (27.8 E% protein) compared with other dual-tracer studies.…”

“…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.…”

“…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.…”

Protein intakes of pregnant women and children in India—protein quality implications

“…DIAAS assessment is now possible in humans, because of the recently (Kashyap et al, 2018;Kashyap et al, 2019;Shivakumar et al, 2019). For this calculation, each food group was represented by a single food.…”

“…For the second and third trimesters, the additional IAA requirements for tissue deposition were calculated separately using mean values of foetal tissue IAA composition from 12-24 and 28-40 weeks, respectively (Widdowson, 1980). The scoring pattern was calculated as the ratio of the body weight-corrected IAA requirement (mgÁkg −1 Áday −1 ) and the body weight-corrected total protein requirement (gÁkg −1 Áday −1 ) for the pregnant women studied (Kuriyan et al, 2019 (Kashyap et al, 2018;Kashyap et al, 2019) were used to calculate the DIAAS of supplementary food sources, that is, legume, egg, and meat, respectively, for pregnant women. For cereal protein, the true ileal IAA digestibility of rice was used from the study on children <2 years (Shivakumar et al, 2019), whereas the digestibility of cow's milk was assumed to be the same as hen's egg protein from the study on adults (Kashyap et al, 2018).…”