Paul Moughan

• Massey University

The quality of a dietary protein refers to its ability to provide the EAAs necessary to meet dietary requirements. There are 9 dietary amino acids that cannot be metabolically produced in the body and therefore must be consumed as part of the diet to avoid adverse metabolic consequences. These essential amino acids (EAAs) serve a variety of roles i...

The recommended amino acid requirements of the infant are based on the amino acid composition of mature human breast milk. The amino acid composition of breast milk is usually determined following either acid or alkaline (for tryptophan) hydrolysis. For accuracy, however, the known effect of hydrolysis time on amino acid composition should be accou...

A promulgated global shift toward a plant-based diet is largely in response to a perceived negative environmental impact of animal food production, but the nutritional adequacy and economic implications of plant-sourced sustainable healthy dietary patterns need to be considered. This paper reviews recent modeling studies using Linear Programming to...

The objective of the review is to revisit the findings of the 2011 Food and Agriculture Organization of the United Nations (FAO) Expert Consultation on Dietary Protein Quality Evaluation in Human Nutrition, and to report on progress on uptake of the findings. It is evident that since 2011 there has been a concerted research effort to enhance an und...

This study evaluated the importance of correcting for amino acids (AAs) 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...

Background The rate of stomach emptying of milk from different ruminant species differs, suggesting that the small intestinal digestibility of nutrients could also differ across these milk types. Objective To determine the small intestinal amino acid (AA) digestibility of raw bovine, caprine, and ovine milk in the piglet as an animal model for the...

Quercetin, a polyphenol antioxidant, is widely distributed in food in the form of glycoside rutin, which is not readily absorbed in the gastrointestinal tract. The microbiota of the colon is known to biotransform rutin, generating quercetin aglycones that can be absorbed. We investigated the role of the ileal and colonic microbiota in rutin biotran...

Background: Organic acid synthesis by the hindgut microbiota is commonly believed to be mainly of fermentable material of dietary origin. Objective: The study aimed to determine the hindgut organic acid synthesis from fermentable material of dietary (mainly fiber) or non-dietary origin, for different types and amounts of dietary fiber in growing...

Vitamins are essential components of enzyme systems involved in normal growth and function. The quantitative estimation of the proportion of dietary vitamins, that is in a form available for utilization by the human body, is limited and fragmentary. This review provides the current state of knowledge on the bioavailability of thirteen vitamins and...

Amino acid (AA) digestibility in humans has been determined conventionally based on oro-ileal AA disappearance. With this approach it is necessary to account for undigested amino acids of body origin (endogenous AAs) found in the ileal digesta. Determination of the endogenous AAs under physiological conditions is not straight forward and the use of...

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 outc...

Background: Infant formula (IF) has to provide at least the same amount of amino acids (AAs) as human milk (HM). AA digestibility in HM and IF was not studied extensively, with no data existing for tryptophan digestibility. Objective: The present study aimed to measure the true ileal digestibility (TID) of total nitrogen and AAs in HM and IF to...

Background: Unabsorbed free amino acids (AAs) at the end of the small intestine result in a potential preventable nutritional loss. Objectives: This study aimed to quantify free AAs in terminal ileal digesta of both humans and pigs to investigate its relevance for the nutritional value of food proteins. Methods: Two studies with three diets we...

This chapter focusses on the role of science, technology and innovation (STI) in transforming the food systems of Asia and the Pacific to achieve long-term environmentally sustainable food and nutritional security (FNS). A “whole of systems” approach is required to address the issues, and that work is urgently needed to define ‘healthy’ diets for d...

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 dete...

Protein is considered to be the most satiating food macronutrient and the satiating effect may be dependent on the source of the protein. The maize-derived protein zein and milk protein casein have been shown previously to lower stomach emptying rate more than dairy whey protein, but the effect of zein on satiety has not been evaluated. The objecti...

The FAO recommends the digestible indispensable amino acid score (DIAAS) to determine protein quality in foods, preferably tested in vivo. Here, the INFOGEST in vitro digestion protocol was applied and supplemented with an analytical workflow allowing the assessment of protein digestibility and DIAAS calculation. The protocol was applied to selecte...

Early nutrition plays a dominant role in infant development and health. It is now understood that the infant diet impacts the gut microbiota and its relationship with gut function and brain development. However, its impact on the microbiota-gut-brain axis has not been studied in an integrative way. The objective here was to evaluate the effects of...

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 gr...

Background and aims GlucoTRIG, based on postprandial plasma insulin and triglyceride concentrations, has been recently developed as a novel index to determine the postprandial metabolic response to the meals. This study aimed to test GlucoTRIG as a measure for ranking composite meals for their metabolic effects. Methods In a randomized cross-over...

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 s...

Background The respective roles of plant- and animal-sourced foods in sustainable healthy diets for humans remain unclear. Nutritional quality and the monetary cost of diets are key criteria among others for sustainable food production. Objective Linear programming (LP) was used to determine the composition of nutritionally adequate dietary patter...

The aim was to study the complementary effect between cereals and pulses on protein quality. The values for the digestible indispensable amino acid score (DIAAS) in cooked cereals and pulses, given alone, and blends of cooked cereals and pulses, were determined. True ileal digestibility (TID) values of amino acids for adult humans were obtained. It...

Background The degree of ileal organic matter (OM) fermentation appears to be comparable to hindgut fermentation in growing pigs. Objectives This study aimed to determine if dietary fiber sources with known different total gastrointestinal tract (GIT) fermentability in humans affect ileal and hindgut microbial communities and ileal fermentation in...

Kiwifruit (KF) fiber, a mixture of soluble and insoluble fibers, elicits mucosal changes in the gastrointestinal tract (GIT). This study aimed to define the nature of these changes in mucosal features throughout the GIT of the growing pig in response to semi-synthetic iso-fiber diets containing cellulose (CEL, low GIT luminal functionality) as the...

The oxygen (O2) concentration of gastrointestinal tract (GIT) contents decreases distally, but little is known about how O2 concentrations are influenced by ingestion of a meal. The O2 concentration in luminal contents at different GIT locations (stomach [cardia and pylorus], proximal, mid‐ and distal small intestine and caecum) and how these conce...

Objectives The protein quality digestible indispensable amino acid scores (DIAAS) require determination of amino acid (AA) bioavailability, which is often quantified as the net disappearance of dietary AAs at the end of the small intestine, so-called true ileal digestibility. It is often assumed that bioavailability is mainly influenced by protein...

It is common practice in food sustainability studies to calculate population-based average protein intakes and express environmental footprints on a gross protein basis. Such analyses, however, assume that the requirement for protein is also expressed as gross protein which is not the case. This ignores the critical role of dietary protein as a sup...

Background Calcium (Ca) can complex with free fatty acids in the gastrointestinal tract (GIT), leading to the formation of insoluble unabsorbable Ca-fatty acid soaps, contributing to the proposed effect of Ca on weight loss in humans. Objectives We determined the effect of dietary Ca concentration and the individual long-chain fatty acids on Ca-fa...

Purpose: The purpose of the study was to determine if an actinidin protease aids gastric digestion and the protein anabolic response to dietary protein. Methods: Hayward green kiwifruit (containing an actinidin protease) and Hort 16A gold kiwifruit (devoid of actinidin protease) were given in conjunction with a beef meal to healthy older subject...

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Determination of whole body rates of protein synthesis, breakdown and net balance in human subjects still has an important role in nutrition research. Quantifying the anabolic response to dietary protein intake is a particularly important application. There are different models with which to accomplish this goal, each with advantages and limitation...

The behavior of fat globules during the gastric digestion of raw and pasteurized cow, goat, and sheep whole milks was studied using a human gastric simulator. Microstructural and physicochemical analysis revealed that, initially, the coagulation of the milks in the human gastric simulator resulted in the majority of the milk fat globules being entr...

Values for the digestible indispensable amino acid score (DIAAS) of a protein are based on true ileal amino acid (AA) digestibility values obtained in adult humans or in the growing pig as an animal model. An experiment was conducted using growing pigs to determine the true ileal digestibility (TID) values of AA in six cooked Chinese pulses (kidney...

Background Recent in silico and in vitro studies have shown that gastrointestinal endogenous proteins (GEP) are a source of bioactive peptides. To date, however, the presence of such peptides in the lumen of the digestive tract has not been demonstrated. Objective We investigated the generation of GEP-derived bioactive peptides in the growing pig...

The effects of orally administered ovine serum immunoglobulin on dental plaque and associated oral immunity in cats were investigated. The two treatment groups consisted of 1) cats that were fed unsupplemented kibble (control diet) and 2) cats that were fed the same kibble but coated with a freeze-dried ovine serum immunoglobulin preparation (ovine...

Coagulation of milk in the stomach is the first crucial step in its digestion. Using a human gastric simulator, the dynamic gastric digestion of goat and sheep skim milk were compared with that of cow skim milk, focusing particularly on their physical characteristics. The gastric contents were analyzed for changes in dry matter and microstructure,...

Background: The traditional dairy-cattle-based industry is becoming increasingly diversified with milk and milk products from non-cattle dairy species. The interest in non-cattle milks has increased because there have been several anecdotal reports about the nutritional benefits of these milks and reports both of individuals tolerating and digestin...

This study characterised the in vitro ileal fermentability of different substrates in the growing pig, adopted as an animal model for the adult human, and compared in vitro ileal and caecal fermentation in the pig. Substrates (arabinogalactan 'AG', cellulose, fructooligosaccharide 'FOS', inulin, mucin, citrus pectin, and resistant starch) were ferm...

Background The quantification of faecal Ca-fatty acid soaps is important to understand how fatty acids behave in the gastrointestinal tract. Objective As current methods to extract Ca-fatty acid soaps from faeces give low recoveries an accurate assay to determine the amount of fatty acid soaps in faeces was developed. Method Ca-fatty acid soaps a...

Spray‐dried animal plasma sourced from bovine, porcine or other animal origin is often used as a main feed ingredient in the diets of weanling piglets to improve growth performance. The objective of this study was to determine the effect of animal plasma in diets on the performance of piglets in the post‐weaning period, with and/or without pathogen...

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...

The amounts of animal-sourced foods required to achieve a least-cost nutritious diet depend on the food prices prevalent in each country. Using linear programming, we determine least-cost dietary patterns in the United States and the constituent amounts of animal-sourced foods. We considered local foods and prices from 2009–2010, and the average en...

Background: This study aimed to develop a novel criterion, GlucoTRIG, to rank meals for healthiness, that considers both glycaemic (serum insulin) and lipaemic (serum triglycerides) responses. Methods: Healthy volunteers (n = 10) were recruited with the aim of deriving a standard GlucoTRIG value for a reference meal. Volunteers consumed the refe...

Dietary fibre fermentation in humans and monogastric animals is considered to occur in the hindgut, but it may also occur in the lower small intestine. This study aimed to compare ileal and hindgut fermentation in the growing pig fed a human-type diet using a combined in vivo/in vitro methodology. Five pigs (23±1.6 kg (mean±SD) bodyweight) were fed...

Dynamic low-amplitude oscillatory rheology was used to study the gelation properties of skim milk gels made at 37°C, using glucono-δ-lactone alone (acid gels) or a combination of glucono-δ-lactone and porcine pepsin (“combination gels”). The protein contents of the skim milks increased in the order goat milk < cattle milk < buffalo milk < sheep mil...

The objective of this study was to evaluate the relationship among the number of bacteria, number of goblet cells, gut mucin gene expression, mucin protein and immunity protein levels of rats fed a diet containing freeze‐dried ovine Ig (FD). Sprague Dawley male rats were used in a 21‐days study and were fed a basal control diet (BD; no Ig) and a te...

Background: Endogenous amino acids (AAs) contribute to terminal ileal digesta and must be corrected for in determining coefficients of true ileal digestibility. Such estimates are also needed for the factorial calculation of AA requirements. Objective: The effect of the form of delivery of dietary AAs on endogenous nitrogen and AA flows at the e...

Background: A highly soluble iron-casein complex has been developed for food fortification purposes with the aim to provide high iron bioavailability. Objective: We aimed to determine the iron bioavailability of the iron-casein complex relative to that of ferrous sulfate (control) when given with whole milk in healthy young women. Methods: A r...

Dietary amino acid digestibility is a fundamental measure of importance in protein quality evaluation. Determining amino acid digestibility in humans, as the disappearance of an amino acid across the total digestive tract, has been discredited. Extensive cecal and colonic microbial metabolism renders fecal estimates of amino acids misleading. True...

Whole-body protein turnover (protein synthesis, breakdown, and net balance) model enables quantification of the response to a variety of circumstances, including the response to meal feeding. In the fed state, the whole-body protein turnover model requires taking account of the contribution of absorbed tracee to the observed total appearance of tra...

The natural food-derived compound curcumin (from turmeric root) is known for its anti-inflammatory and anti-oxidant effects. However, due to its poor solubilty when consumed in isolation, it is poorly bioavailable. In this crossover study we compared the bioavailability of curcumin from a meal containing either curcumin powder, turmeric powder or g...

Immunoglobulin (Ig) is the one of the main anti‐infective components of blood, colostrum and breast milk. It is the unique glycoprotein that defends the body from harmful bacteria, viruses and other environmental pathogens by either binding to them or by forming an encapsulating barrier. The expansion of antimicrobial and immunomodulatory products...

Objectives This study aimed to compare ileal and hindgut fermentations in the pig model using a combined in vivo/in vitro methodology. Methods Pigs (23 kg bodyweight, n = 5) were fed a human-type diet for 15 days. On day 15, pigs were euthanased and the small intestine was immediately dissected out and ligated in three equal lengths. Digesta from...

Intrinsically-labeled dietary proteins have been used to trace various aspects of digestion and absorption, including quantifying the contribution of dietary protein to observed post-prandial amino acid and protein kinetics in human subjects. Quantification of the rate of appearance in peripheral blood of an unlabeled (tracee) amino acid originatin...

Many in vivo, in vitro and combined in vivo–in vitro methodologies have been developed to study the mechanisms involved and sites of nutrient digestion and absorption in the gastrointestinal tract. Moreover, different approaches within each of these methodologies have also been developed. Some of the methodologies/approaches can be applied to multi...

The effect of kiwi fruit at two dietary levels on the adaptation of intestinal fermentation over time in the growing pig was studied. A semi-synthetic fibre-free diet and two semi-synthetic diets containing kiwi fruit as a model fibre source (133 or 266 g/kg (DM basis); 28 or 48 g fibre/kg) were formulated and the diets contained titanium dioxide a...

Background: Actinidin, a cysteine protease in kiwifruit (KF), increases both the gastric digestion and gastric-emptying rate of beef muscle protein. Objective: This study aimed to determine the relation between the rate of digested nitrogen entering the small intestine (SI; a function of the extent of gastric digestion and gastric-emptying rate)...

Background The form of dietary nitrogen (free peptides or intact proteins) may influence the amount of endogenous amino acids found at the terminal ileum of the pig, and it has been speculated that hydrolyzed dietary protein may lead to increased endogenous amino acids. Objective To compare the effect of dietary free peptides on ileal endogenous n...

Background: The loss of endogenous (nondietary) amino acids (AAs) from the gastrointestinal tract (GIT) is an important component underlying the adult human dietary requirement for protein and essential AAs (EAAs). Although data with regard to endogenous AA losses to the end of the small intestine have been published, to our knowledge there are no...

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:...

Traditionally, the study of nutrition has been based on a reductionist approach, reducing a food to its constituent nutrients and then investigating the effects of these nutrients, either singly or together, on metabolism and metabolic outcomes. Nutrients are not consumed in isolation but, rather, are consumed in the form of foods. For this reason,...

Background Substantial microbial fermentation may occur mainly in the lower small intestine (SI) of human adults, but there is no established methodology to determine this. Objective The study aimed to develop a combined in vivo and in vitro methodology for ileal fermentation based on the pig as an animal model for digestion in human adults. Meth...

Protein is the only dietary macronutrient required for life. As such, it is reasonable to consider dietary protein as the centerpiece of a healthy eating pattern. To do so requires consideration of what type of protein should be eaten. Account should be taken of the quality of the protein, the density of the protein in the protein food source, and...

One of the limitations for ranking foods and meals for healthiness on the basis of the glycaemic index (GI) is that the GI is subject to manipulation by addition of fat. Postprandial lipemia, defined as a rise in circulating triglyceride containing lipoproteins following consumption of a meal, has been recognised as a risk factor for the developmen...

Dietary protein quality has been recognized as a critical issue by international authorities because it can affect important functions of the body. To predict protein quality, the FAO introduced the Digestible Indispensable Amino Acid Score. This score depends on ileal amino acid (AA) digestibility; therefore, the assumption is made that AAs are no...

Protein is the most satiating macronutrient and is source dependent, with whey protein thought to be particularly satiating. The purported satiating effect of whey protein may be due to the unique mixture of proteins in whey or to the major constituent individual proteins (β-lactoglobulin and α-lactalbumin). The objective of the study was to compar...

The world currently faces one of its greatest challenges, that of feeding in a sustainable manner, nine billion people by the year 2050. It is estimated by the FAO that meat consumption alone will double by 2050. There will be an important role for the pig and poultry industries in meeting this challenge. Considerable progress has been made over th...

Body protein and therefore dietary protein have a central role metabolically. Dietary protein is digested in the gastrointestinal tract by the action of both mammalian and bacterial enzymes, and small peptides and free amino acids are absorbed mainly in the small intestine by a tightly controlled integrated system. Absorbed amino acids may have spe...

Background: It has been assumed that short-chain fatty acids (SCFAs) in the colon originate mainly from dietary fiber fermentation. However, SCFAs in the colon are also produced from the fermentation of nondietary material. Objectives: We aimed to predict the relative contributions of dietary and nondietary substrates in the production of SCFAs...

Dietary protein is considered more satiating than carbohydrate, and whey protein is more satiating than other protein sources. The purported satiating effect of whey protein may be due to direct effects of the unique mixture of proteins in whey, due to the effects of peptides released upon digestion and/or its amino acid composition. The objective...

Human gastrointestinal endogenous proteins (GEP) include the proteins mucins, serum albumin, digestive enzymes, and proteins from sloughed epithelial and microbial-cells. GEP play a vital role in the digestion of food, but are also simultaneously digested by proteases and peptidases of the gastrointestinal tract (GIT). Recent studies suggest that d...

The biological processes underlying the partitioning of amino acids and energy during animal growth are well understood qualitatively. However, if a deeper mechanistic understanding is to be achieved, such as to allow generalised predictions of growth outcomes, these biological processes need to be described quantitatively, along with critical cont...

The aim of this review is to identify the origin and implications of a nondietary material present in digesta and feces that interferes with the determination of dietary fiber in gastrointestinal contents. Negative values for ileal and fecal digestibility of dietary fiber are commonly reported in the literature for monogastric animal species, inclu...

Gastric protein hydrolysis may influence gastric emptying rate and subsequent protein digestibility in the small intestine. This study examined the gastric hydrolysis of dietary protein from raw and roasted almonds in the growing pig as a model for the adult human. The gastric hydrolysis of almond proteins was quantified by performing tricine-sodiu...

The intestinal epithelium of adult humans acts as a differentially permeable barrier that separates the potentially harmful contents of the lumen from the underlying tissues. Any dysfunction of this boundary layer that disturbs the homeostatic equilibrium between the internal and external environments may initiate and sustain a biochemical cascade...

A recently proposed paradigm suggests that, like their dietary counterparts, digestion of gastrointestinal endogenous proteins (GEP) may also produce bioactive peptides. With an aim to test this hypothesis, in vitro digests of four GEP namely; trypsin (TRYP), lysozyme (LYS), mucin (MUC), serum albumin (SA) and a dietary protein chicken albumin (CA)...

The Food and Agriculture Organization of the United Nations recently recommended the adoption of a new and improved scoring system (Digestible Indispensable Amino Acid Score [DIAAS]) to quantify dietary protein quality. The DIAAS is based on the relative digestible content of the indispensable amino acids (IAAs) and the amino acid requirement patte...

The effect of dietary kiwifruit inclusion level on the digestibility of kiwifruit fibre and dietary nutrients was studied. Ileal cannulated pigs (50 ± 1.9 kg) were fed a fibre-free diet for seven days (n = 14) followed by kiwifruit-containing diets (133 or 266 g kiwifruit/kg dry matter) (n = 7) for 44 days followed by the fibre-free diet (n = 14) f...

It is well known that endogenous bioactive proteins and peptides play a substantial role in the body's first line of immunological defence, immune-regulation and normal body functioning. Further, the peptides derived from the luminal digestion of proteins are also important for body function. For example, within the peptide database BIOPEP (http://...