Massey Research Online - Browsing by Author "Smith NW"

Browsing by Author "Smith NW"

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A Mathematical Model for the Hydrogenotrophic Metabolism of Sulphate-Reducing Bacteria.
(Frontiers Media S.A., 2019-07-17) Smith NW; Shorten PR; Altermann E; Roy NC; McNabb WC; Greening C
Sulphate-reducing bacteria (SRB) are studied across a range of scientific fields due to their characteristic ability to metabolise sulphate and produce hydrogen sulphide, which can lead to significant consequences for human activities. Importantly, they are members of the human gastrointestinal microbial population, contributing to the metabolism of dietary and host secreted molecules found in this environment. The role of the microbiota in host digestion is well studied, but the full role of SRB in this process has not been established. Moreover, from a human health perspective, SRB have been implicated in a number of functional gastrointestinal disorders such as Irritable Bowel Syndrome and the development of colorectal cancer. To assist with the study of SRB, we present a mathematical model for the growth and metabolism of the well-studied SRB, Desulfovibrio vulgaris in a closed system. Previous attempts to model SRB have resulted in complex or highly specific models that are not easily adapted to the study of SRB in different environments, such as the gastrointestinal tract. We propose a simpler, Monod-based model that allows for easy alteration of both key parameter values and the governing equations to enable model adaptation. To prevent any incorrect assumptions about the nature of SRB metabolic pathways, we structure the model to consider only the concentrations of initial and final metabolites in a pathway, which circumvents the current uncertainty around hydrogen cycling by SRB. We parameterise our model using experiments with varied initial substrate conditions, obtaining parameter values that compare well with experimental estimates in the literature. We then validate our model against four independent experiments involving D. vulgaris with further variations to substrate availability. Further use of the model will be possible in a number of settings, notably as part of larger models studying the metabolic interactions between SRB and other hydrogenotrophic microbes in the human gastrointestinal tract and how this relates to functional disorders.
Alternative protein-based foods must contribute to micronutrient adequacy
(Taylor and Francis Group on behalf of the Royal Society of New Zealand, 2024-01-29) Smith NW; Fletcher AJ; McNabb WC
Sustainable diets must consider health, economic, environmental, and social outcomes. The development and production of alternative protein foods should also make these considerations. We examined the nutritional role of these foods, with New Zealand (NZ) as a case study. We used the DELTA Model® to assess 2020 NZ nutrient supply. We then simulated the substitution of 50% of meat supply (by mass) with various plant protein sources (soy, peas, beans, and mushroom), and observed the impact on nutrient supply. NZ had an undersupply of calcium (38%), vitamin E (34% deficit), dietary fibre (20%), potassium (13%), and vitamin C (10%) compared to population requirements. Contrastingly, there was sufficient protein and amino acid supply for an additional 2.4 million people. Halving of meat supply resulted in decreased availability for potassium (21% deficit), zinc (17%), folate (10%), and iron (9%). Soy proved the best nutritional replacement for meat, with reduced deficits for all undersupplied nutrients compared to 2020. Replacement with other modelled protein sources resulted in greater nutrient deficits. The nutritional implications beyond protein must be considered when making dietary substitutions. There are clear public health reasons to fortify alternative proteins with both the nutrients lost in substitution and those already in deficit.
Animal and plant-sourced nutrition: Complementary not competitive
(CSIRO Publishing, 2022-05) Smith NW; Fletcher AJ; Hill JP; McNabb WC; Pembleton K
Debate on the sustainability of the global food system often compares the environmental, economic and health impacts of plant- and animal-sourced foods. This distinction can mask the considerable variation in impacts across and within these food groups. Moreover, the nutritional benefits of these food groups are insufficiently discussed. In this review, we highlight the nutritional contribution to the current global food system of both plant- and animal-sourced foods and place their impacts on human health in the global context. We highlight how the comparison of the environmental impacts of foods via life cycle analyses can change on the basis of the functional unit used, particularly the use of mass as opposed to nutrient content or nutrient richness. We review the literature on the affordability of nutrient-adequate diets, demonstrating the presence of both plant- and animal-sourced foods in affordable nutritious diets. Finally, we address the potential of alternative food sources that are gaining momentum, to ask where they may fit in a sustainable food system. We conclude that there is a clear place for both plant- and animal-sourced foods in future sustainable food systems, and a requirement for both for sustainable global nutrition; as such, the two groups are complementary and not competitive.
Competition for Hydrogen Prevents Coexistence of Human Gastrointestinal Hydrogenotrophs in Continuous Culture.
(Frontiers Media S.A., 2020-05-29) Smith NW; Shorten PR; Altermann E; Roy NC; McNabb WC; Kappler U
Understanding the metabolic dynamics of the human gastrointestinal tract (GIT) microbiota is of growing importance as research continues to link the microbiome to host health status. Microbial strains that metabolize hydrogen have been associated with a variety of both positive and negative host nutritional and health outcomes, but limited data exists for their competition in the GIT. To enable greater insight into the behaviour of these microbes, a mathematical model was developed for the metabolism and growth of the three major hydrogenotrophic groups: sulphate-reducing bacteria (SRB), methanogens and reductive acetogens. In batch culture simulations with abundant sulphate and hydrogen, the SRB outcompeted the methanogen for hydrogen due to having a half-saturation constant 106 times lower than that of the methanogen. The acetogen, with a high model threshold for hydrogen uptake of around 70 mM, was the least competitive. Under high lactate and zero sulphate conditions, hydrogen exchange between the SRB and the methanogen was the dominant interaction. The methanogen grew at 70% the rate of the SRB, with negligible acetogen growth. In continuous culture simulations, both the SRB and the methanogen were washed out at dilution rates above 0.15 h-1 regardless of substrate availability, whereas the acetogen could survive under abundant hydrogen conditions. Specific combinations of conditions were required for survival of more than one hydrogenotroph in continuous culture, and survival of all three was not possible. The stringency of these requirements and the inability of the model to simulate survival of all three hydrogenotrophs in continuous culture demonstrates that factors outside of those modelled are vital to allow hydrogenotroph coexistence in the GIT.
Complex network analysis and health implications of nutrient trade
(Elsevier BV, 2024-03) Silvestrini MM; Smith NW; Fletcher AJ; McNabb WC; Sarti FM
Food trade plays a key role in global nutrition, but the essential nutrients within this trade are understudied. We investigated the global nutrient trade network from 1986 to 2020, examining the relationship with income level and health outcomes. Bilateral nutrient trade data for 48 nutrients and 254 countries/economies was produced, made accessible through an interactive online application. Nutrients of interest in the context of food security and health (protein, calcium, iron, and vitamins A and B12) were examined using network analysis, animated graphs, and logistic regression to demonstrate the inequitable nature of nutrient trade, but its positive role in current nutrition-related disease. Food trade policy should be set with micronutrient content and deficiency in mind to address food security, nutrition, and health.
Correction: Barnsley et al. Lifetime Climate Impacts of Diet Transitions: A Novel Climate Change Accounting Perspective. Sustainability 2021, 13, 5568
(MDPI (Basel, Switzerland), 2022-07) Barnsley JE; Chandrakumar C; Gonzalez-Fischer C; Eme PE; Bourke BEP; Smith NW; Dave LA; McNabb WC; Clark H; Frame DJ; Lynch J; Roche JR
The authors would like to make the following corrections about the published paper The changes are as follows: (1) Replacing the Conflicts of Interest: Conflicts of Interest: The authors declare no conflict of interest. with Conflict of Interest: The Ministry for Primary Industries (MPI) is the regulator for New Zealand’s entire primary sector. As regulator, we are responsive to the needs of all food-producing industries and have a wide range of other responsibilities. In a practical sense, our role includes protecting New Zealand from biological risk, increasing food production, minimising environmental impacts, and ensuring the food we produce in New Zealand is safe for consumers. The primary sector is wide-ranging and includes our arable and horticulture industries, as well as our red meat, dairy, fisheries and aquaculture industries. The authors apologize for any inconvenience caused and state that the scientific conclusions are unaffected. The original publication has also been updated.
Estimating cropland requirements for global food system scenario modeling
(Frontiers Media S.A., 2022-12-16) Smith NW; Fletcher AJ; Millard P; Hill JP; McNabb WC; Ridoutt BG
Introduction: The production of plant crops is foundational to the global food system. With the need for this system to become more sustainable while feeding an increasing global population, tools to investigate future food system scenarios can be useful to aid decision making, but are often limited to a calorie- or protein-centric view of human nutrition. Methods: Here, a mathematical model for forecasting the future cropland requirement to produce a given quantity of crop mass is presented in conjunction with the DELTA Model®: an existing food system scenario model calculating global availability of 29 nutrients against human requirements. The model uses national crop yield data to assign yield metrics for 137 crops. Results: The crops with the greatest variation between high and low yielding production were specific nuts, fruits, and vegetables of minor significance to global nutrient availability. The nut crop group showed the greatest overall yield variation between countries, and thus the greatest uncertainty when forecasting the cropland requirement for future increases in production. Sugar crops showed the least overall yield variation. The greatest potential for increasing global food production by improving poor yielding production was found for the most widely grown crops: maize, wheat, and rice, which were also demonstrated to be of high nutritional significance. Discussion: The combined cropland and nutrient availability model allowed the contribution of plant production to global nutrition to be quantified, and the cropland requirement of future food production scenarios to be estimated. The unified cropland estimation and nutrient availability model presented here is an intuitive and broadly applicable tool for use in global food system scenario modeling. It should benefit future research and policy making by demonstrating the implications for human nutrition of changes to crop production, and conversely the implications for cropland requirement of food production scenarios aimed at improving nutrition.
Evaluation of Protein Adequacy From Plant-Based Dietary Scenarios in Simulation Studies: A Narrative Review
(Elsevier Inc on behalf of the American Society for Nutrition, 2024-02) Soh BXP; Smith NW; R von Hurst P; McNabb WC
Although a diet high in plant foods can provide beneficial nutritional outcomes, unbalanced and restrictive plant-based diets may cause nutrient deficiencies. Protein intake from these diets is widely discussed, but the comparison of animal and plant proteins often disregards amino acid composition and digestibility as measurements of protein quality. Poor provision of high-quality protein may result in adverse outcomes, especially for individuals with increased nutrient requirements. Several dietary modeling studies have examined protein adequacy when animal-sourced proteins are replaced with traditional and novel plant proteins, but no review consolidating these findings are available. This narrative review aimed to summarize the approaches of modeling studies for protein intake and protein quality when animal-sourced proteins are replaced with plant foods in diet simulations and examine how these factors vary across age groups. A total of 23 studies using dietary models to predict protein contribution from plant proteins were consolidated and categorized into the following themes-protein intake, protein quality, novel plant-based alternatives, and plant-based diets in special populations. Protein intake from plant-based diet simulations was lower than from diets with animal-sourced foods but met country-specific nutrient requirements. However, protein adequacy from some plant-sourced foods were not met for simulated diets of children and older adults. Reduced amino acid adequacy was observed with increasing intake of plant foods in some scenarios. Protein adequacy was generally dependent on the choice of substitution with legumes, nuts, and seeds providing greater protein intake and quality than cereals. Complete replacement of animal to plant-sourced foods reduced protein adequacy when compared with baseline diets and partial replacements.
Evolution of global food trade network and its effects on population nutritional status
(Elsevier BV, 2023-06-03) Silvestrini MM; Smith NW; Sarti FM; Marangoni AG
Changes in food systems during the last decades fostered the establishment of global food networks based on exchanges between countries with different income levels. Recent studies explored configuration and factors associated with trade networks of specific food items during limited periods; however, there is lack of evidence on evolution of trade networks of foods for human consumption and its potential effects on population nutritional status. We present the evolution of the global trade network of foods for human consumption from 1986 to 2020, according to country income level, and we explore potential effects of country network centrality and globalization processes on the prevalence of overweight and obesity. Results show intensification of international food trade and globalization processes in the period of analysis with implications for population nutritional status worldwide.
Examination of hydrogen cross-feeders using a colonic microbiota model
(BioMed Central Ltd, 2021-12) Smith NW; Shorten PR; Altermann E; Roy NC; McNabb WC
BACKGROUND: Hydrogen cross-feeding microbes form a functionally important subset of the human colonic microbiota. The three major hydrogenotrophic functional groups of the colon: sulphate-reducing bacteria (SRB), methanogens and reductive acetogens, have been linked to wide ranging impacts on host physiology, health and wellbeing. RESULTS: An existing mathematical model for microbial community growth and metabolism was combined with models for each of the three hydrogenotrophic functional groups. The model was further developed for application to the colonic environment via inclusion of responsive pH, host metabolite absorption and the inclusion of host mucins. Predictions of the model, using two existing metabolic parameter sets, were compared to experimental faecal culture datasets. Model accuracy varied between experiments and measured variables and was most successful in predicting the growth of high relative abundance functional groups, such as the Bacteroides, and short chain fatty acid (SCFA) production. Two versions of the colonic model were developed: one representing the colon with sequential compartments and one utilising a continuous spatial representation. When applied to the colonic environment, the model predicted pH dynamics within the ranges measured in vivo and SCFA ratios comparable to those in the literature. The continuous version of the model simulated relative abundances of microbial functional groups comparable to measured values, but predictions were sensitive to the metabolic parameter values used for each functional group. Sulphate availability was found to strongly influence hydrogenotroph activity in the continuous version of the model, correlating positively with SRB and sulphide concentration and negatively with methanogen concentration, but had no effect in the compartmentalised model version. CONCLUSIONS: Although the model predictions compared well to only some experimental measurements, the important features of the colon environment included make it a novel and useful contribution to modelling the colonic microbiota.
Food-breastmilk combinations alter the colonic microbiome of weaning infants: an in silico study
(American Society for Microbiology, 2024-09) da Silva VG; Smith NW; Mullaney JA; Wall C; Roy NC; McNabb WC; Garrido D
The introduction of solid foods to infants, also known as weaning, is a critical point for the development of the complex microbial community inhabiting the human colon, impacting host physiology in infancy and later in life. This research investigated in silico the impact of food-breastmilk combinations on growth and metabolite production by colonic microbes of New Zealand weaning infants using the metagenome-scale metabolic model named Microbial Community. Eighty-nine foods were individually combined with breastmilk, and the 12 combinations with the strongest influence on the microbial production of short-chain fatty acids (SCFAs) and branched-chain fatty acids (BCFAs) were identified. Fiber-rich and polyphenol-rich foods, like pumpkin and blackcurrant, resulted in the greatest increase in predicted fluxes of total SCFAs and individual fluxes of propionate and acetate when combined, respectively, with breastmilk. Identified foods were further combined with other foods and breastmilk, resulting in 66 multiple food-breastmilk combinations. These combinations altered in silico the impact of individual foods on the microbial production of SCFAs and BCFAs, suggesting that the interaction between the dietary compounds composing a meal is the key factor influencing colonic microbes. Blackcurrant combined with other foods and breastmilk promoted the greatest increase in the production of acetate and total SCFAs, while pork combined with other foods and breastmilk decreased the production of total BCFAs. IMPORTANCE Little is known about the influence of complementary foods on the colonic microbiome of weaning infants. Traditional in vitro and in vivo microbiome methods are limited by their resource-consuming concerns. Modeling approaches represent a promising complementary tool to provide insights into the behavior of microbial communities. This study evaluated how foods combined with other foods and human milk affect the production of short-chain fatty acids and branched-chain fatty acids by colonic microbes of weaning infants using a rapid and inexpensive in silico approach. Foods and food combinations identified here are candidates for future experimental investigations, helping to fill a crucial knowledge gap in infant nutrition.
Global nutrient content embedded in food losses and waste: Identifying the sources and magnitude along the food supply chain
(Elsevier Ltd on behalf of Institution of Chemical Engineers, 2024-11) Beuving M; McNabb WC; Smith NW; Teodosiu C
Reducing food losses and waste (FLW) can contribute to improving nutrient availability to meet the nutritional needs of the global population. Identifying foods that contribute most to nutrient content in FLW is crucial for developing effective strategies to reduce FLW. Here, we assessed the current literature for quality and consistency of FLW data, and then evaluated the quantity of nutrients that are wasted as a consequence of FLW, identifying the primary food sources contributing to this on a global scale. Several FLW definitions and quantification methods were identified in the literature, making it difficult to compare FLW data and estimates of nutrient content in FLW between existing studies. The nutrient content in global FLW was determined for 29 nutrients from 99 food commodities with the DELTA Model®, after which the contribution of each food group to the nutrient content of FLW was calculated. An indicator was developed to assess the potential impact of resolving FLW on global nutrient availability. Nutrient content in FLW was highest for phosphorus (69 % of global requirement), tryptophan (62 %), thiamine (61 %), methionine (58 %) and histidine (54 %). For 17 out of 29 nutrients, >40 % of the global requirement was embedded in FLW. Cereals contributed most to nutrient losses, followed by fruits and vegetables. According to the indicator, rice, wheat, vegetables, maize, and milk provided the greatest opportunity for increasing nutrient supply via reduction of FLW, due to the combination of waste rates and nutrient density. Our findings highlight the importance of broadening FLW research beyond food mass to incorporate nutritional aspects as important indicators, and to identify key food items to reduce FLW for the improvement of nutrient availability.
Hydrogen cross-feeders of the human gastrointestinal tract.
(Taylor & Francis Group, 2019-01-01) Smith NW; Shorten PR; Altermann EH; Roy NC; McNabb WC
Hydrogen plays a key role in many microbial metabolic pathways in the human gastrointestinal tract (GIT) that have an impact on human nutrition, health and wellbeing. Hydrogen is produced by many members of the GIT microbiota, and may be subsequently utilized by cross-feeding microbes for growth and in the production of larger molecules. Hydrogenotrophic microbes fall into three functional groups: sulfate-reducing bacteria, methanogenic archaea and acetogenic bacteria, which can convert hydrogen into hydrogen sulfide, methane and acetate, respectively. Despite different energy yields per molecule of hydrogen used between the functional groups, all three can coexist in the human GIT. The factors affecting the numerical balance of hydrogenotrophs in the GIT remain unconfirmed. There is increasing evidence linking both hydrogen sulfide and methane to GIT diseases such as irritable bowel syndrome, and strategies for the mitigation of such health problems through targeting of hydrogenotrophs constitute an important field for further investigation.
Lifetime climate impacts of diet transitions: a novel climate change accounting perspective
(MDPI (Basel, Switzerland), 2021-05-17) Barnsley JE; Chandrakumar C; Gonzalez-Fischer C; Eme PE; Bourke BEP; Smith NW; Dave LA; McNabb WC; Clark H; Frame DJ; Lynch J; Roche JR; Carolan M
Dietary transitions, such as eliminating meat consumption, have been proposed as one way to reduce the climate impact of the global and regional food systems. However, it should be ensured that replacement diets are indeed nutritious and that climate benefits are accurately accounted for. This study uses New Zealand food consumption as a case study for exploring the cumulative climate impact of adopting the national dietary guidelines and the substitution of meat from hypothetical diets. The new GWP* metric is used as it was designed to better reflect the climate impacts of the release of methane than the de facto standard 100-year Global Warming Potential metric (GWP100). A transition at age 25 to the hypothetical dietary guideline diet reduces cumulative warming associated with diet by 7 to 9% at the 100th year compared with consuming the average New Zealand diet. The reduction in diet-related cumulative warming from the transition to a hypothetical meat-substituted diet varied between 12 and 15%. This is equivalent to reducing an average individual's lifetime warming contribution by 2 to 4%. General improvements are achieved for nutrient intakes by adopting the dietary guidelines compared with the average New Zealand diet; however, the substitution of meat items results in characteristic nutrient differences, and these differences must be considered alongside changes in emission profiles.
Mathematical modelling supports the existence of a threshold hydrogen concentration and media-dependent yields in the growth of a reductive acetogen.
(Springer Nature Limited, 2020-05-01) Smith NW; Shorten PR; Altermann E; Roy NC; McNabb WC
The bacterial production of acetate via reductive acetogenesis along the Wood-Ljungdahl metabolic pathway is an important source of this molecule in several environments, ranging from industrial bioreactors to the human gastrointestinal tract. Here, we contributed to the study of reductive acetogens by considering mathematical modelling techniques for the prediction of bacterial growth and acetate production. We found that the incorporation of a hydrogen uptake concentration threshold into the models improves their predictions and we calculated this threshold as 86.2 mM (95% confidence interval 6.1-132.6 mM). Monod kinetics and first-order kinetics models, with the inclusion of two candidate threshold terms or reversible Michaelis-Menten kinetics, were compared to experimental data and the optimal formulation for predicting both growth and metabolism was found. The models were then used to compare the efficacy of two growth media for acetogens. We found that the recently described general acetogen medium was superior to the DSMZ medium in terms of unbiased estimation of acetogen growth and investigated the contribution of yeast extract concentration to acetate production and bacterial growth in culture. The models and their predictions will be useful to those studying both industrially and environmentally relevant reductive acetogenesis and allow for straightforward adaptation to similar cases with different organisms.
Modeling the Contribution of Milk to Global Nutrition
(Frontiers Media S.A., 2022-01-13) Smith NW; Fletcher AJ; Hill JP; McNabb WC; Skeaff SA
Nutrient-rich foods play a major role in countering the challenges of nourishing an increasing global population. Milk is a source of high-quality protein and bioavailable amino acids, several vitamins, and minerals such as calcium. We used the DELTA Model, which calculates the delivery of nutrition from global food production scenarios, to examine the role of milk in global nutrition. Of the 29 nutrients considered by the model, milk contributes to the global availability of 28. Milk is the main contributing food item for calcium (49% of global nutrient availability), Vitamin B2 (24%), lysine (18%), and dietary fat (15%), and contributes more than 10% of global nutrient availability for a further five indispensable amino acids, protein, vitamins A, B5, and B12, phosphorous, and potassium. Despite these high contributions to individual nutrients, milk is responsible for only 7% of food energy availability, indicating a valuable contribution to global nutrition without necessitating high concomitant energy intakes. Among the 98 food items considered by the model, milk ranks in the top five contributors to 23 of the 29 nutrients modeled. This quantification of the importance of milk to global nutrition in the current global food system demonstrates the need for the high valuation of this food when considering future changes to the system.
The classification and evolution of bacterial cross-feeding
(Frontiers Media S.A., 2019-01-01) Smith NW; Shorten PR; Altermann E; Roy NC; McNabb WC; Harcombe W
Bacterial feeding has evolved toward specific evolutionary niches and the sources of energy differ between species and strains. Although bacteria fundamentally compete for nutrients, the excreted products from one strain may be the preferred energy source or a source of essential nutrients for another strain. The large variability in feeding preferences between bacterial strains often provides for complex cross-feeding relationships between bacteria, particularly in complex environments such as the human lower gut, which impacts on the host's digestion and nutrition. Although a large amount of information is available on cross-feeding between bacterial strains, it is important to consider the evolution of cross-feeding. Adaptation to environmental stimuli is a continuous process, thus understanding the evolution of microbial cross-feeding interactions allows us to determine the resilience of microbial populations to changes to this environment, such as changes in nutrient supply, and how new interactions might emerge in the future. In this review, we provide a framework of terminology dividing bacterial cross-feeding into four forms that can be used for the classification and analysis of cross-feeding dynamics. Under the proposed framework, we discuss the evolutionary origins for the four forms of cross-feeding and factors such as spatial structure that influence their emergence and subsequent persistence. This review draws from both the theoretical and experimental evolutionary literature to provide a cross-disciplinary perspective on the evolution of different types of cross-feeding.
The Classification and Evolution of Bacterial Cross-Feeding
(Frontiers Media S.A., 2019-05-14) Smith NW; Shorten PR; Altermann E; Roy NC; McNabb WC; Harcombe W
Bacterial feeding has evolved toward specific evolutionary niches and the sources of energy differ between species and strains. Although bacteria fundamentally compete for nutrients, the excreted products from one strain may be the preferred energy source or a source of essential nutrients for another strain. The large variability in feeding preferences between bacterial strains often provides for complex cross-feeding relationships between bacteria, particularly in complex environments such as the human lower gut, which impacts on the host's digestion and nutrition. Although a large amount of information is available on cross-feeding between bacterial strains, it is important to consider the evolution of cross-feeding. Adaptation to environmental stimuli is a continuous process, thus understanding the evolution of microbial cross-feeding interactions allows us to determine the resilience of microbial populations to changes to this environment, such as changes in nutrient supply, and how new interactions might emerge in the future. In this review, we provide a framework of terminology dividing bacterial cross-feeding into four forms that can be used for the classification and analysis of cross-feeding dynamics. Under the proposed framework, we discuss the evolutionary origins for the four forms of cross-feeding and factors such as spatial structure that influence their emergence and subsequent persistence. This review draws from both the theoretical and experimental evolutionary literature to provide a cross-disciplinary perspective on the evolution of different types of cross-feeding.
The role of holistic nutritional properties of diets in the assessment of food system and dietary sustainability
(Taylor and Francis Group, 2023) Dave LA; Hodgkinson SM; Roy NC; Smith NW; McNabb WC
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 β-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.
The role of meat in the human diet: evolutionary aspects and nutritional value
(Oxford University Press on behalf of the American Society of Animal Science, 2023-04-15) Leroy F; Smith NW; Adesogan AT; Beal T; Iannotti L; Moughan PJ; Mann N
Implications Aspects of human anatomy, digestion, and metabolism diverged from other primates, indicating evolutionary reliance on, and compatibility with, substantial meat intake. Implications of a disconnect from evolutionary dietary patterns may contribute to today’s burden of disease, increasing the risk for both nutrient deficiencies and chronic diseases. Meat supplies high-quality protein and various nutrients, some of which are not always easily obtained with meat-free diets and are often already suboptimal or deficient in global populations. Removal of meat comes with implications for a broad spectrum of nutrients that need to be accounted for, whereas compensatory dietary strategies must factor in physiological and practical constraints. Although meat makes up a small part (<10%) of global food mass and energy, it delivers most of the global vitamin B12 intake and plays a substantial role in the supply of other B vitamins, retinol, long-chain omega-3 fatty acids, several minerals in bioavailable forms (e.g., iron and zinc), and a variety of bioactive compounds with health-improving potential (e.g., taurine, creatine, and carnosine). As a food matrix, meat is more than the sum of its individual nutrients. Moreover, within the diet matrix, it can serve as a keystone food in food-based dietary interventions to improve nutritional status, especially in regions that rely heavily on cereal staples. Efforts to lower global meat intake for environmental or other reasons beyond a critical threshold may hinder progress towards reducing undernutrition and the effects this has on both physical and cognitive outcomes, and thereby stifle economic development. This is particularly a concern for populations with increased needs and in regions where current meat intake levels are low, which is not only pertinent for the Global South but also of relevance in high-income countries.

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