Determinants of amino acid bioavailability from ingested protein in relation to gut health

Abstract

Purpose of review The current review provides an update on the recent research developments regarding amino acid bioavailability in conditions of both good health and gut disorders. Recent findings Determination of amino acid bioavailability is complex and invasive. Minimally invasive methods using stable isotopes have been developed for humans. Data were collected in different models – humans, pigs and rats with various procedures – leading to interstudy variability. They mainly focused on either plant protein or the effect of food processing on animal protein. Plant protein in their original food matrix (legumes, grains, nuts) are generally less digestible (about 80%) than animal protein (meat, egg, milk; about 93%). Food processing has a limited impact on animal protein but its effect might be higher on plant protein. Few studies have documented the effect of gut disorders on protein digestibility, except in gastric bypass where paradoxical effects were reported. Data are needed to identify the amplitude of protein malabsorption in diseases such as inflammatory bowel disease or environmental enteric dysfunction. Summary The past 5 years have seen a renewed interest in amino acid bioavailability in view of assessing protein quality to support current shifts in protein sourcing. Methodological developments have been performed and several studies have reported values in various models. The question of protein digestibility in gut disorders remains poorly addressed.

Protein Quality in Perspective: A Review of Protein Quality Metrics and Their Applications

“…Some studies have indeed been conducted in humans to determine the ileal digestibility of proteins [ 64 , 65 , 66 ]. However, ileal digesta collection in human is complicated [ 67 ], and most data available to date on ileal digestibility of dietary proteins has come from animal models [ 68 ]. Based on Figure 4 , ileal digesta from pigs and rats are preferred after human ileal digesta, but over human faecal digesta [ 63 ].…”

The association between dietary branched-chain amino acids and the risk of cardiovascular diseases in Chinese patients with type 2 diabetes: A hospital-based case–control study

“…Some believed that the elevation of serum BCAA levels is probably a consequence of disease rather than a cause (46) since endogenous factors, such as insulin, are able to regulate BCAA metabolism and degradation (47). In addition, the increase in amino acid oxidation was likely to be a consequence of impaired protein synthesis, which was caused by a limitation of diet-derived amino acid intake (48). Therefore, higher BCAA intake could decrease protein degradation and oxidative stress (49), while adequate BCAA consumption is essential for maintaining glucose homeostasis and body weight (9).…”

Comparison of True Ileal Amino Acid Digestibility between Adult Humans and Growing Pigs

“…Importantly, when examining the digestibility 2 Determined using 2-factor ANOVA model. 3 Correlation for true ileal amino acid digestibility between pig and human across the seven protein sources. 4 Overall mean = mean of all amino acids (reactive lysine is included but lysine is not included in these averages).…”

“…Less invasive indirect methods to determine AA digestibility or availability in humans, such as the dual-isotope method (4) and indicator AA oxidation (IAAO) method (5), are also options. However, these methods, although showing much promise, cannot be considered routine methods and either are still under development or have not been fully validated (3,6). With the IAAO method, relatively costly intrinsic labeling of the food is not required, which is the case for the dualisotope approach, but AA availability observations are limited to one AA per assay period, which requires multiple testing days.…”