The kinetics of amino acid disappearance in the small intestine is related to the extent of amino acids absorbed in growing pigs.

This study evaluated the importance of a correction for amino acids (AA) released into the hindgut on a measure of AA absorption kinetics and tested whether AA absorption kinetics are related to the extent of AA absorption using the growing pig as a model for humans. Thirty-six nine-week-old pigs (22·3 kg) received a diet containing whey protein as the sole protein source for 8 d. Pigs received their last meal containing the indigestible marker titanium dioxide before being euthanised at 1, 2, 3, 4, 6 and 12 h post-feeding. The entire content of each gastrointestinal tract (GIT) region was collected to determine AA released into the hindgut, and the kinetics and extent of AA absorption (uncorrected and corrected for AA entering the hindgut). Amounts of AA released into the hindgut increased over time (e.g. 33 and 180 mg of Glu for 4 and 6 h post-feeding). The corrected apparent amount of each AA absorbed from the GIT lumen after 4 h post-feeding was generally lower (P ≤ 0·05) than the uncorrected counterpart. Differences in both the kinetics and extent of AA absorption were observed across AA. For example, the time to reach half of the apparent AA absorption (T50) was 1·5 and 3·4 h for Met and Arg, respectively, whereas their extent of apparent absorption was 93 and 73 %. Negative correlations between parameters related to kinetics and the extent of apparent absorption were observed (e.g. for T50 r = -0·81; P < 0·001). The kinetics of AA absorption is related to the extent of AA absorption.

An Accurate Estimate of the Amino Acid Content of Human Milk Collected from Chinese Women Adjusted for Differences in Amino Acid Digestibility.

BACKGROUND: The amino acid (AA) composition of human milk is used to define the AA requirements of the infant. Thus, it is important that estimates of composition be as complete and accurate as possible. When determining AA composition using standard hydrolysis methods, some AAs are progressively destroyed while others are incompletely released. For accuracy, AA composition needs to be determined using multiple hydrolysis times. The true ileal digestibility of AAs also needs to be taken into consideration. OBJECTIVE: The objective was to bring together AA compositional (determined using multiple hydrolysis intervals) and digestibility data determined using the piglet to give an estimate of the absorbed AA profile of human milk with reference in particular to Asian females. METHODS: Mature milk was collected from Chinese females. AA analysis using multiple hydrolysis intervals and a nonlinear regression model was used to accurately estimate AA composition. Human milk, as well as a protein-free diet, were fed to piglets (n = 6), and ileal digesta were collected (piglet age, 21 d) to determine the true ileal AA digestibility of AAs in human milk. RESULTS: True ileal AA digestibility coefficients ranged from (mean ± standard error of the mean) 0.61 ± 0.081 for tyrosine to 1.01 ± 0.030 for tryptophan, with a digestibility for total nitrogen of 0.90 ± 0.013. Convergence criteria were met for the modeling for each AA, and the model had a level of significance of P < 0.0001 for each AA. The amount of available AAs (total AA content as per the model prediction multiplied by the true ileal AA digestibility coefficient determined in the piglet) are reported. CONCLUSIONS: An estimate of the absorbed AA profile of mature milk collected from Chinese females is provided. For the first time, data is presented for cysteine.

In Vitro Ileal Fermentation is Affected More by the Fiber Source Fermented than the Ileal Microbial Composition in Growing Pigs.

Background: The fermentation of undigested material in the ileum is quantitatively important. However, the respective contributions of the microbial composition and the substrate to ileal fermentation are unclear. Objective: This aim was to investigate the contribution of microbial composition and fiber source to in vitro ileal fermentation outcomes. Methods: Thirteen ileal cannulated female pigs (Landrace/Large White; 9-wk-old; 30.5 kg body weight) were given diets containing black beans, wheat bread, chickpeas, peanuts, pigeon peas, sorghum, or wheat bran as the sole protein source for 7 d (100 g protein/kg dry matter diet). On day 7, ileal digesta were collected and stored at -80°C for microbial analysis and in vitro fermentation. For each diet, a pooled ileal inoculum was prepared to ferment different fiber sources (cellulose, pectin, arabinogalactan, inulin, fructooligosaccharides, and resistant starch) for 2 h at 37°C. Organic matter fermentability and organic acid production were determined following in vitro fermentation. Data were analyzed using a 2-way ANOVA (inoculum × fiber). Results: Forty-five percent of the identified genera in the digesta differed across diets. For instance, the number of Lactococcus was 115-fold greater (P ≤ 0.05) in the digesta of pigs fed the pigeon pea diet than for pigs fed the wheat bran diet. For both in vitro organic matter fermentability and organic acid production, there were significant (P ≤ 0.05) interactions between the inoculum and the fiber source. For instance, pectin and resistant starch resulted in 1.6- to 31-fold more (P ≤ 0.05) lactic acid production when fermented by the pigeon pea inoculum than other inocula. For specific fiber sources, statistically significant correlations were found between the number of bacteria from certain members of the ileal microbial community and fermentation outcomes. Conclusions: Both the fiber source fermented and the ileal microbial composition of the growing pig affected in vitro fermentation; however, the effect of the fiber source was predominant.Curr Dev Nutr 2023;x:xx.

Available Lysine in Foods as Determined in Adult Ileostomates.

BACKGROUND: When foods are subjected to heat and pressure, a proportion of lysine is structurally altered and some will revert to lysine because of acid hydrolysis during amino acid analysis. Altered lysine molecules may be partly absorbed but are not utilized post-absorption. OBJECTIVES: A guanidination-based bioassay has been developed to determine true ileal digestible reactive lysine but it was only used in animal models (pig and rat). The objective of this study was to apply the assay and determine whether there is a difference between true ileal digestible total lysine and true ileal digestible reactive lysine in adult human ileostomates. METHODS: Six cooked or processed foods were analyzed for total lysine and reactive lysine. Six adults with a fully functioning ileostomy (4 women and 2 men; age range: 41-70 y; BMI: 20.8-28.1) participated. Foods for which total lysine > reactive lysine (cooked black beans, toasted wheat bread, and processed wheat bran), as well as a protein-free diet, were consumed by the ileostomates (n = 5 to 8; test food meals contained 25 g protein) and ileal digesta was collected. Each food was ingested twice by each participant, and the digesta was pooled. The order of foods for each participant was determined according to a Youden square. True ileal digestible total lysine and true ileal digestible reactive lysine were determined and a 2-way ANOVA model was used to analyze data. RESULTS: True ileal digestible reactive lysine was significantly lower than true ileal digestible total lysine for cooked black beans, toasted wheat bread, and processed wheat bran by 89%, 55%, and 85%, respectively (P< 0.05). CONCLUSIONS: True ileal digestible reactive lysine was lower than true ileal digestible total lysine, similar to that previously reported in pigs and rats, demonstrating the importance of determining the true ileal digestible reactive lysine contents of processed foods.

Cooked Rice-Based and Wheat-Based Food Structure Influenced Digestion Kinetics and Glycemic Response in Growing Pigs.

BACKGROUND: How starch-based food structure can affect the rate and extent of digestion in the small intestine and resulting glycemic response is not properly understood. One possible explanation is that food structure influences gastric digestion, which subsequently determines digestion kinetics in the small intestine and glucose absorption. However, this possibility has not been investigated in detail. OBJECTIVES: Using growing pigs as a digestion model for adult humans, this study aimed to investigate how physical structure of starch-rich foods affects small intestinal digestion and glycemic response. METHODS: Male growing pigs (21.7 ± 1.8 kg, Large White × Landrace) were fed one of the 6 cooked diets (250-g starch equivalent) with varying initial structures (rice grain, semolina porridge, wheat or rice couscous, or wheat or rice noodle). The glycemic response, small intestinal content particle size and hydrolyzed starch content, ileal starch digestibility, and portal vein plasma glucose were measured. Glycemic response was measured as plasma glucose concentration collected from an in-dwelling jugular vein catheter for up to 390 min postprandial. Portal vein blood samples and small intestinal content were measured after sedation and euthanasia of the pigs at 30, 60, 120, or 240 min postprandial. Data were analyzed with a mixed-model ANOVA. RESULTS: The plasma glucose Δmaxoverall and iAUCoverall for couscous and porridge diets (smaller-sized diets) were higher than that of intact grain and noodle diets (larger-sized diets): 29.0 ± 3.2 compared with 21.7 ± 2.6 mg/dL and 5659 ± 727 compared with 2704 ± 521 mg/dL⋅min, for the smaller-sized and larger-sized diets, respectively (P < 0.05). Ileal starch digestibility was not significantly different between the diets (P ≥ 0.05). The iAUCoverall was inversely related to the starch gastric emptying half-time of the diets (r = -0.90, P = 0.015). CONCLUSIONS: Starch-based food structure affected the glycemic response and starch digestion kinetics in the small intestine of growing pigs.

In vitro digestibility of dietary proteins and in vitro DIAAS analytical workflow based on the INFOGEST static protocol and its validation with in vivo data.

The FAO recommends the digestible indispensable amino acid score (DIAAS) to determine protein quality in foods, preferably tested in vivo. Here, the INFOGESTin vitrodigestion protocol was applied and supplemented with an analytical workflow allowing the assessment of protein digestibility and DIAAS calculation. The protocol was applied to selected samples WPI, zein, collagen, black beans, pigeon peas, All-Bran®, and peanuts. The total protein digestibility, digestibility of individual amino acids (AA), and DIAAS values were established and compared with in vivo data for the same substrates. Total protein digestibility (total Nitrogen, r = 0.7, P < 0.05; primary amines (OPA), r = 0.6, P < 0.02; total AA, r = 0.6, P < 0.02) and digestibility of individual AA (r = 0.6, P < 0.0001) were in good agreement, between in vitro and in vivo, with a mean difference of 1.2 %. In vitro DIAAS was highly correlated with DIAAS obtained from in vivo true ileal digestibility values (r = 0.96, R2 = 0.89, P < 0.0001) with a mean difference of 0.1 %.

The role of holistic nutritional properties of diets in the assessment of food system and dietary sustainability.

Advancing sustainable diets for nutrition security and sustainable development necessitates clear nutrition metrics for measuring nutritional quality of diets. Food composition, nutrient requirements, and dietary intake are among the most common nutrition metrics used in the current assessment of sustainable diets. Broadly, most studies in the area classify animal-source foods (ASF) as having a substantially higher environmental footprint in comparison to plant-source foods (PSF). As a result, much of the current dietary advice promulgates diets containing higher proportions of PSF. However, this generalization is misleading since most of these studies do not distinguish between the gross and bioavailable nutrient fractions in mixed human diets. The bioavailability of essential nutrients including ß-carotene, vitamin B-12, iron, zinc, calcium, and indispensable amino acids varies greatly across different diets. The failure to consider bioavailability in sustainability measurements undermines the complementary role that ASF play in achieving nutrition security in vulnerable populations. This article critically reviews the scientific evidence on the holistic nutritional quality of diets and identifies methodological problems that exist in the way the nutritional quality of diets is measured. Finally, we discuss the importance of developing nutrient bioavailability as a requisite nutrition metric to contextualize the environmental impacts of different diets.

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

BACKGROUND: It is not feasible to determine the true ileal amino acid (AA) digestibility of protein sources in humans on a routine basis, and the growing pig has been recommended as an animal model for this purpose but requires further validation. OBJECTIVES: To determine and compare true ileal AA digestibility between adult human ileostomates and growing cannulated pigs for a range of food proteins. METHODS: Seven protein sources (black beans, bread, collagen, pigeon peas, wheat bran, whey protein isolate, and zein) that spanned the range of digestibilities typically seen in foods were evaluated. Six female growing pigs received each of the protein sources, as well as a protein-free diet, and digesta were collected via ileal T-cannula. Adult human ileostomates consumed the same protein sources (5-8 ileostomates, depending on the protein source), as well as a protein-free diet, and digesta were collected. Titanium dioxide and celite were included in the diets as indigestible markers. True ileal AA digestibility coefficients were determined. RESULTS: There was a significant effect of protein source (P ≤ 0.001) for all AAs. The effect of species was not significant (P > 0.05) except for total lysine (but not for available lysine). When analyzed within diets, the statistically significant species effect for true lysine digestibility was found for black beans only. Pig and human digestibility values were generally highly and significantly (P ≤ 0.05) correlated. A linear regression equation derived for true ileal AA digestibility (given as coefficients) determined in the human and pig for the overall mean of all AAs was (y = human, x = pig) y = 1.00x - 0.010, with the slope not statistically significant (P > 0.05) from unity and the intercept not different (P > 0.05) from zero. CONCLUSIONS: True ileal AA digestibility values determined in the growing pig can be directly used for predicting digestibility in adult humans.

Structural changes in milk from different species during gastric digestion in piglets.

This study investigated the structural and physicochemical changes that occur in milk, a naturally designed complex structured emulsion, during gastric digestion using the bottle-fed piglet as an animal model. The gastric digestions of cow, goat, and sheep milk were compared in male piglets euthanized at different postfeeding times to collect the stomach chyme. The cow and noncow milks separated into curd (aggregated caseins) and liquid (mostly soluble whey) phases in the piglet's stomach. For milk from all the species, the curd remained longer in the stomach because of its slow disintegration, whereas the liquid phase emptied readily. The majority of the fat globules were found to be entrapped within the protein network of the curd. The rate of release of fat globules was strongly dependent on the breakdown of the surrounding protein network of the curd. The consistency of the gastric curds changed as digestion progressed, with goat and sheep milk curds having relatively softer curd consistency and less fused protein networks, especially toward the end of digestion. This might have led to the lower protein and fat retention in the goat and sheep milk curds and relatively faster gastric emptying of these nutrients from goat and sheep milk in comparison to cow milk. This in vivo study provided new and enhanced understanding of the mechanisms of the gastric digestion of milk from different species. It may have implications for developing bioinspired structures for the controlled digestion and delivery of nutrients.

Correction: Tracking physical breakdown of rice- and wheat-based foods with varying structures during gastric digestion and its influence on gastric emptying in a growing pig model.

Correction for 'Tracking physical breakdown of rice- and wheat-based foods with varying structures during gastric digestion and its influence on gastric emptying in a growing pig model' by Joanna Nadia et al., Food Funct., 2021, DOI: 10.1039/D0FO02917C.

Tracking physical breakdown of rice- and wheat-based foods with varying structures during gastric digestion and its influence on gastric emptying in a growing pig model.

There is currently a limited understanding of the effect of food structure on physical breakdown and gastric emptying of solid starch-based foods during gastric digestion. Moisture uptake, pH, particle size, rheological, and textural properties of six solid starch-based diets from different sources (Durum wheat and high amylose white rice) and of different macrostructures (porridge, native grain, agglomerate/couscous, and noodle) were monitored during 240 min of gastric digestion in a growing pig model. Changes in the physical properties of the gastric digesta were attributed to the influence of gastric secretions and gastric emptying, which were both dependent on the buffering capacity and initial macrostructure of the diets. Differences between the proximal and distal stomach regions were found in the intragastric pH and texture of the gastric digesta. For example, rice couscous, which had the smallest particle size and highest buffering capacity among the rice-based diets, had the shortest gastric emptying half-time and no significant differences between proximal and distal stomach digesta physical properties. Additionally, a relationship between gastric breakdown rate, expressed as gastric softening half-time from texture analysis, and gastric emptying half-time of dry matter was also observed. These findings provide new insights into the breakdown processes of starch-based solid foods in the stomach, which can be beneficial for the development of food structures with controlled rates of breakdown and gastric emptying during digestion.

Determination of True Ileal Amino Acid Digestibility in the Growing Pig for Calculation of Digestible Indispensable Amino Acid Score (DIAAS).

Digestible indispensable amino acid score (DIAAS) has been recommended by the FAO for the evaluation of protein quality in human foods, but the application of DIAAS is currently limited because of a lack of published data on the true ileal amino acid (AA) digestibility of AAs in foods. The importance of DIAAS is highlighted. To calculate DIAAS, it is necessary to determine the true ileal AA digestibility of human foods using the growing pig as an animal model for the human based on previous FAO recommendations. A method is described in detail in Supplemental Methods to determine the true ileal AA digestibility of foods for humans using the pig as a model for the adult human. Adoption of the method will enable consistency in the development of databases on predicted true ileal AA digestibility in human foods for the calculation of DIAAS.

Cooking Conditions Affect the True Ileal Digestible Amino Acid Content and Digestible Indispensable Amino Acid Score (DIAAS) of Bovine Meat as Determined in Pigs.

Background: Cooking processes affect the physical, chemical, and structural properties of meat proteins. Cooking may also affect the protein quality of meat, as indicated by the true ileal digestibility of individual amino acids, the content of each truly digestible amino acid, and the digestible indispensable amino acid score (DIAAS). Objective: The study aimed to determine the effect of the cooking process (raw, not cooked; boiled; grilled; pan-fried; roasted) of beef on true (standardized) ileal amino acid digestibility, true ileal digestible amino acid content, and DIAAS. Methods: Beef topside steak was subjected to one of the following conditions: raw, boiled, grilled, pan-fried, or roasted, followed by mincing. The growing pig was used as an animal model for the adult human. Diets containing the raw or cooked meats (10% crude protein content) were fed to growing pigs (n = 6 per diet; mean ± SEM bodyweight, 23.6 ± 0.48 kg) and samples of terminal ileal digesta were collected under anesthesia. True ileal amino acid digestibility of the beef was determined and DIAAS values were calculated. Results: There were only minor differences in true ileal amino acid digestibility across cooking conditions with all amino acids having true ileal amino acid digestibility in the range of 90-100%. In general, boiled meat had the highest true ileal digestible amino acid content (total of 724 g/kg dry matter), and roasted meat the lowest (total of 641 g/kg dry matter; P < 0.001). The DIAAS was greater (P < 0.001) for the raw, boiled, and pan-fried meat treatments (97-99%) than for roasted meat (91%) or grilled meat (80%). The high DIAAS (range 80-99%) across cooking conditions confirms that bovine meat is a high-quality protein source. Conclusion: Cooking conditions affect the true ileal digestible amino acid content and DIAAS of beef, as determined with the use of the pig model.