(P16-010-23) Protein Quality of 15N Protein From Faba Bean Consumed As Whole Grains in Healthy Humans

Objectives: The recommended transition towards more plant-based diets, in particular containing legumes, requires a wider knowledge on plant protein bioavailability. Faba beans are cultivated in different latitudes and are used increasingly in human nutrition. We aimed to assess their nutritional protein quality in healthy volunteers equipped with an intestinal tube to implement the ileal ¹⁵N balance method.

Methods: Participants were equipped with a naso-ileal tube. After fasting overnight, they ingested a test meal, which consisted of dehulled, mashed faba bean (20 g protein in appr. 250 g portion) that was intrinsically labelled with ¹⁵N. Ileal content, plasma and urine samples were collected over an 8 h postprandial period. Undigested nitrogen (N) and amino acids (AAs) were determined, and subsequently ileal digestibility and DIAAS score. The measurement of postprandial deamination allowed to calculate the Net Postprandial Protein Utilization (NPPU). Results are presented as mean ± SD.

Results: Of the 18 healthy adults recruited, nine completed the study (7 M, 2 F, aged 33 ± 10 years, BMI 24.7 ± 2.6). The ileal N digestibility was 84.1 ± 7.7%. Postprandial deamination represented 18.7 ±3.5 % of ingested N and the NPPU was 65.8 ± 9.6%. The ileal digestibility of individual AAs varied from 85.4 ± 14.5 % for histidine to 94.6 ± 3.8 % for glutamine/glutamic acid, and the mean digestibility of individual AA was approximately 6 % higher than digestibility of N, reaching 90 ± 6 %. Histidine and tryptophan were the first limiting AA (DIAAS = 0.76 when calculated by legume-specific N-to-protein conversion factor 5.4 and DIAAS = 0.66 when using the factor 6.25). Sulfur amino acids were limiting in a lesser extend (DIA ratio = 0.92 for N x 5.4 and 0.8 for N x 6.25).

Conclusions: This study pioneeringly determines the N and AA bioavailability of faba bean ingested as whole grains. Faba bean AA digestibility was good (around 90 %) but overall protein quality was penalized by the limited histidine and tryptophan content.

Funding Sources: Strategic Research Council at Academy of Finland