Determination of Indispensable Amino Acid Digestibility of the Red Kidney Bean in Humans Using a Dual Stable Isotope Tracer Method.

Protein quality of the red kidney bean (RKB), a common source of dietary protein, has been assessed using the protein digestibility-corrected amino acid score (PDCAAS) determined in animal models using mainly oro-fecal digestibility. More recently, the FAO recommended to use digestible indispensable amino acid score (DIAAS) instead of PDCAAS but highlighted insufficient data on true ileal indispensable amino acid (IAA) digestibility of proteins because amino acids are absorbed in the ileum. Using a recently developed dual stable isotope tracer method, we aimed to measure each IAA digestibility as representation of true ileal digestibility of the RKB, Phaseolus vulgaris, in humans consuming a typical Jamaican meal. RKB-IAAs were intrinsically labeled by adding 2H2O to the plants. Uniformly labeled-[13C]-spirulina (standard protein) was added to a meal prepared with the labeled RKB and fed to 10 healthy adults (5 males, 5 females) in a nonrandomized trial as primed/intermittent doses to achieve a steady state IAA enrichment in plasma. Enrichment of 2H- and 13C-labeled IAA in plasma and the bean was measured by mass spectrometry. Each IAA digestibility (except tryptophan and histidine) was calculated as the ratio of plasma 2H-IAA to meal 2H-IAA divided by the ratio of plasma 13C-IAA to meal 13C-IAA adjusted for loss of 2H-atom during transamination and digestibility of spirulina. Adequate IAA labeling (>1000 ppm 2H excess) and plasma plateau isotopic enrichment were achieved. Mean RKB-IAA digestibility (%) was 79.4 ± 0.5, ranging from 69.0 ± 1.2 (threonine) to 85.7 ± 1.7 (lysine). The dual stable isotope tracer digestibility data are similar to published oro-fecal digestibility supporting substantial nitrogen exchange in the colon. The individual IAA digestibility is useful to derive DIAAS to replace PDCAAS. Using published RKB-IAA composition, extrapolated DIAAS was 0.63 based on the lowest score for methionine. https://register. gov; ID: NCT-04118517.

Thomas DJ ，Riley C ，Devi S ，Kurpad AV ，Preston T ，Francis R ，Chambers B ，Brown O ，Badaloo AV ... -  《-》

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

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. 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. 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. 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. 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).

Kashyap S ，Varkey A ，Shivakumar N ，Devi S ，Reddy B H R ，Thomas T ，Preston T ，Sreeman S ，Kurpad AV ... -  《-》

Pinto Bean Amino Acid Digestibility and Score in a Mexican Dish with Corn Tortilla and Guacamole, Evaluated in Adults Using a Dual-Tracer Isotopic Method.

Ultra-processed foodstuffs have been replacing traditional beans with tortillas in the Mexican diet in the last decades. Therefore, scientific support is needed to promote a return to good-quality traditional dishes. This study aims to evaluate the amino acid digestibility and score of pinto beans (Phaseolus vulgaris) consumed with corn tortillas and guacamole in adults using the dual-tracer method. The pinto beans were intrinsically labeled using 250 mL of 2H2O (99.8%) per 19 L pot with 3 plants. A paste of cooked beans on toasted corn tortillas and guacamole topping were administered to 3 male and 3 female adults (21-25 years old; BMI, 19-23.5 kg/m2). The protocol was plateau feeding given along with U-[13C]-spirulina protein to evaluate indispensable amino acid (IAA) digestibility using the dual-tracer method. Blood samples were taken in the plateau state. The digestibility of each IAA of the bean protein was calculated by the ratio of its enrichment in the beans to the spirulina in the meal and its appearance in plasma collected in the plateau state, as a percentage corrected by spirulina digestibility. Additionally, the digestible IAA score (DIAAS) was calculated. The 2H enrichment of IAA in the pinto beans was 471 parts per million excess. The isotopic enrichment of 2H and 13C in IAA at 5-8 hours presented plateau states with mean CVs of 12.2% and 13.3%, respectively. The mean digestibility of IAA from pinto beans was 77% ± 1.6%, with the lowest value for threonine. The DIAAS calculated with respect to the pattern requirement for children older than 3 years, adolescents, and adults was 83%, with methionine and cysteine being the limiting amino acids. A Mexican dish of pinto beans, tortillas, and guacamole is a good source of protein as evaluated in adults and could be promoted as a nutritious snack. The assay is registered with the Ethical Committee of the Centro de Investigación en Alimentación y Desarrollo, A.C. as CE/015/2019.

Calderón de la Barca AM ，Martínez-Díaz G ，Ibarra-Pastrana ÉN ，Devi S ，Kurpad AV ，Valencia ME ... -  《-》

Measurement of True Indispensable Amino Acid Digestibility by the Dual Isotope Tracer Technique: A Methodological Review.

The digestible indispensable amino acid score uses ileal digestibility of each indispensable amino acid (IAA) of a dietary protein to calculate its protein quality. However, true ileal digestibility, which is the exclusive sum of digestion and absorption of a dietary protein up to the terminal ileum, is difficult to measure in humans. It is traditionally measured using invasive oro-ileal balance methods but can be confounded by endogenous secreted protein in the intestinal lumen, although the use of intrinsically labeled protein corrects for this. A recent, minimally invasive dual isotope tracer technique is now available to measure true IAA digestibility of dietary protein sources. This method involves simultaneous ingestion of 2 intrinsically but differently (stable) isotopically labeled proteins, a (2H or 15N-labeled) test protein and (13C-labeled) reference protein whose true IAA digestibility is known. Using a plateau-feeding protocol, the true IAA digestibility is determined by comparing the steady state ratio of blood to meal test protein IAA enrichment to the similar reference protein IAA ratio. The use of intrinsically labeled protein also distinguishes between IAA of endogenous and dietary origin. The collection of blood samples makes this method minimally invasive. As the α-15N and α-2H atoms of AAs of the intrinsically labeled protein are prone to label loss because of transamination, underestimation of digestibility, appropriate correction factors need to be employed when using 15N or 2H labeled test protein. The true IAA digestibility values of highly digestible animal protein by the dual isotope tracer technique are comparable to that measured by direct oro-ileal balance measurements, but no data are yet available for proteins with lower digestibility. A major advantage is that the minimally invasive method allows for true IAA digestibility measurement in humans across different age groups and physiological conditions.

Kashyap S ，Bellam HRR ，Preston T ，Devi S ，Kurpad AV ... -  《-》

Protein-quality evaluation of complementary foods in Indian children.

The types of food in complementary feeding of infants and young children are important for growth and development. Food protein quality, as measured by the Digestible Indispensable Amino Acid Score (DIAAS), requires the determination of true ileal digestibility of indispensable amino acids (IAAs) in children. First, the aim of this study was to measure the true ileal IAA digestibility of 4 (rice, finger millet, mung bean, and hen egg) commonly consumed complementary foods in children aged <2 y using the dual-isotope tracer method. Second, we calculated the DIAAS of complementary feeding diets and their relation to stunting in a representative Indian rural population. Rice, finger millet, and mung bean were intrinsically labeled with deuterium oxide (2H2O), whereas egg was labeled through oral dosing of hens with a uniformly 2H-labeled amino acid mixture. True ileal IAA digestibility was determined by the dual-isotope tracer technique. The DIAAS of complementary food protein was calculated in children aged 1-3 y from a nationally representative survey to evaluate its relation with stunting. True ileal IAA digestibility was lowest in mung bean (65.2% ± 7.1%), followed by finger millet (68.4 %± 5.3%) and rice (78.5% ± 3.5%), and was highest for egg (87.4% ± 4.0%). There was a significant inverse correlation of complementary food DIAAS with stunting in survey data (r = -0.66, P = 0.044). The addition of egg or milk to nationally representative complementary diets theoretically improved the DIAAS from 80 to 100. The true ileal IAA digestibility of 4 foods commonly consumed in complementary diets showed that the DIAAS was associated with stunting and reinforces the importance of including animal source food (ASF) in diets to improve growth. This trial was registered at http://ctri.nic.in/clinicaltrials/login.php as CTRI/2017/02/007921.

Shivakumar N ，Kashyap S ，Kishore S ，Thomas T ，Varkey A ，Devi S ，Preston T ，Jahoor F ，Sheshshayee MS ，Kurpad AV ... -  《-》