Measurement of protein digestibility in humans by a dual-tracer method

Background: Recent evaluations of the risk of dietary protein deficiency have indicated that protein digestibility may be a key limiting factor in the provision of indispensable amino acids (IAAs), particularly for vulnerable populations living in challenging environments where intestinal dysfunction may exist. Since the digestion of protein occurs only in the small intestine, and the metabolic activity of colonic bacteria confounds measurements at the fecal level, there is a need to develop noninvasive protein digestibility measurements at the ileal level. Objective: We used a dual-tracer method with stable isotopes to characterize the digestibility of uniformly labeled [13C]-spirulina protein as a standard protein, in comparison to a mixture of 2H-labeled crystalline amino acids, and then demonstrated the use of this standard protein to measure the digestibility of selected legumes (chick pea and mung bean) through the use of proteins that were intrinsically labeled with 2H. Design: The digestibility of uniformly labeled [13C]-spirulina was first measured in 6 healthy volunteers (3 males and 3 females) by feeding it along with a standard mixture of 2H-labeled amino acids, in a dual-tracer, plateau-fed test meal approach. Next, intrinsically labeled legume protein digestibility was studied with a similar dual-tracer approach, with uniformly labeled [13C]-spirulina as the standard, when processed differently before consumption. Results: The average digestibility of IAA in spirulina protein was 85.2%. The average IAA digestibility of intrinsically 2H-labeled chick pea and mung bean protein was 56.6% and 57.7%, respectively. Dehulling of mung bean before ingestion increased the average IAA digestibility by 9.9% in comparison to whole mung bean digestibility. Conclusions: An innovative, minimally invasive “dual-stable-isotope” method was developed to measure protein digestibility, in which the ingestion of an intrinsically 2H-labeled test protein along with a 13C-labeled standard protein of known digestibility allows for an accurate measure of digestion and absorption of the intrinsically labeled protein. This minimally invasive method is critical to redefining protein quality and will aid in revisiting human protein requirements in different settings and in vulnerable populations. This trial was registered at Clinical Trials Registry—India as CTRI/2017/11/010468

Dietary Diversity Predicts the Adequacy of Micronutrient Intake in Pregnant Adolescent Girls and Women in Bangladesh, but Use of the 5-Group Cutoff Poorly Identifies Individuals With Inadequate Intake

Background: The Minimum Dietary Diversity for Women (MDD-W) indicator based on a 10-food group women dietary diversity score (WDDS-10) has been validated to assess dietary quality in nonpregnant women. Little is known about its applicability in pregnant women, and specifically pregnant adolescent girls with higher nutrient requirements. Objectives: This study aimed to 1) compare the adequacy of micronutrient intakes between pregnant adolescent girls and women, 2) examine the performance of WDDS-10 in predicting the mean probability of adequacy (MPA) of 11 micronutrients, and 3) assess how well the MDD-W cutoff of 5 groups performed in pregnant adolescent girls and women. Methods: We used data from a 2015 household survey in Bangladesh (n = 600). Nutrient intakes were estimated with a multiple-pass 24-h recall and WDDS-10 was assessed through the use of a list-based method. Multiple linear regression models adjusted for geographical clustering assessed the association between WDDS-10 and MPA. Sensitivity and specificity analysis assessed the accuracy of MDD-W in correctly classifying individuals into high (MPA \u3e0.6) or low MPA. Results: Dietary intakes of pregnant adolescent girls and women were similar in energy intake, WDDS-10 (5.1 ± 1.4), MPA (0.40 ± 0.12), and micronutrient intakes. Probabilities of adequacy were ∼0.30 for riboflavin, vitamin B-12, calcium, and zinc; 0.12-0.15 for folate; 0.16-0.19 for vitamin A; and extremely low for iron at 0.01. The WDDS-10 was significantly associated with MPA in both groups and predicted MPA equally well at population level (SD of residuals 0.11 for both). Use of the 5-food groups cutoff for MDD-W to classify individuals\u27 diets into MPA \u3e0.6, however, resulted in a low correct classification (∼40%). A cutoff of 6 food groups markedly improved correct classification. Conclusions: The WDDS-10 predicted MPA equally well for pregnant adolescent girls and women at population level. The MDD-W indicator performed poorly in classifying individuals with MPA \u3e0.6