Context and Perspectives for Establishing a Novel Database for Protein Quality of Human Foods, as Proposed by a Joint Food and Agriculture Organization of the United Nations/International Atomic Energy Agency Expert Technical Meeting in October 2022.

United Nations agencies have a long history of leading work on establishing global human nutrient requirements. Dietary protein contributes to metabolism and homeostasis and plays an essential role in human health for growth, maintenance, reproduction, and immune function (or immunity). Accurately defining the quantity and quality of protein provided by foods and diets required to meet human nutritional needs is essential to achieving global environmental and nutrition goals. There have been many scientific developments related to protein quality over the past decades, with the preferred method being the scoring approach that relates the capacity of protein sources to provide an adequate amount and proportion of nitrogen and indispensable amino acids (IAAs) in a bioavailable form (often referred to as digestibility). Questions surrounding the scoring approach and IAA metabolic availability have been discussed during past and recent expert consultations. Recently, an Food and Agriculture Organization of the United Nations/International Atomic Energy Agency technical meeting, held in Vienna, 10-13 October, 2022, reviewed and updated evidence and related methods on protein requirements and protein quality assessment and designed a framework for the development of a Protein Digestibility Database to aid dialog on the evaluation of protein quality and protein sufficiency in different populations. The database should be a living document and align with national food compositional databases.

PROTOCOL: Measuring diet-related consumer behaviours relevant to low- and middle-income countries to advance food systems research: An evidence and gap map.

This is the protocol for a evidence and gap map. The main objective of this evidence and gap map is to provide access to a systematic overview of available indicators for diet-related consumer behaviours relevant to LMICs, to support policy makers and researchers to develop, monitor and revise food policies and programmes to leverage food systems transformations for healthier and more sustainable diets.

Why Food System Transformation Is Essential and How Nutrition Scientists Can Contribute.

BACKGROUND: The International Union of Nutritional Sciences held its 21st International Congress of Nutrition in October 2017 in Buenos Aires, Argentina under the theme - From Sciences to Nutrition Security. In addition to multiple sessions on food systems and their links to diet, nutrition and health, the Congress closing lecture focused on the need to transform food systems so as to increase their capacity to provide healthy diets, making a call for greater involvement of nutrition scientists. SUMMARY: This article presents the main messages of that lecture, providing (i) an overview of global nutrition trends and their links to diets, food environments and food systems, (ii) a synopsis of the current global momentum for food system transformation and (iii) the need for nutrition scientists to leverage this momentum in terms of increased evidence generation and policy advocacy. Key Messages: Poor quality diets are increasingly leading to the compromising of human health as never before; the prevalence of undernutrition persists and remains acute in vulnerable regions, and hunger is increasing concomitantly with an unprecedented rise in overweight, obesity and nutrition-related non-communicable diseases. Increasing access to healthy diets through faster, stronger implementation of supply and demand-side strategies that address the underlying drivers of today's faulty food systems is imperative to solve these problems, as well as to address related environmental and economic costs. The global momentum for such action is increasing, but the evidence base needed to galvanize governments and hold stakeholders accountable remains yet a fledgling. To date, inputs from nutrition scientists to this reform agenda have been weak, especially given the unique contributions the field can make in terms of rigorous analysis and technical advice. Strengthened participation will require innovations in metrics and methodologies, combined with new thinking on what constitutes viable evidence and a greater willingness to engage with private sector agri-food actors.

Linking agriculture and nutrition education to improve infant and young child feeding: Lessons for future programmes.

Agriculture and food systems play a central role in nutrition by supplying nutritious, healthy and affordable foods. When integrated with nutrition education for behaviour change, agricultural interventions that supply diverse affordable foods from all food groups have great scope for improving young child and family diets. In 2014, process reviews were conducted in Cambodia and Malawi of food security projects that provided agricultural support and community-based nutrition education on improved infant and young child feeding (IYCF). In both countries, household visits were carried out with mothers/caregivers, and interviews and Focus Group Discussions (FGDs) were conducted with purposively selected project stakeholders (53 in Cambodia, 170 in Malawi), including government staff from the agriculture and health sectors. Results highlight that adoption of improved IYCF practices was facilitated by participation in nutrition education and practical cooking sessions, and supportive family and community structures. Barriers faced by families and caregivers were identified, such as women's workload and lack of access to high quality foods, namely fruits, vegetables, legumes, nuts and animal source foods. Implementation challenges regarding coordination of cross-sectoral targeting strategies and capacities of extension services to sustain community-based IYCF nutrition education need to be addressed to improve programme effectiveness and impact. The project lessons from Cambodia and Malawi are useful for integrated agriculture-IYCF nutrition education programmes to help ensure better young child nutrition outcomes.

Improving food composition data quality: Three new FAO/INFOODS guidelines on conversions, data evaluation and food matching.

Food composition data play a key role in many sectors and the availability of quality data is critically important. Since 1984, the International Network of Food Data Systems (INFOODS) has been working towards improving food composition data quality and availability, including the development and updating of standards, guidelines and tools for food composition. FAO/INFOODS has recently published three comprehensive guidelines to improve and harmonise the compilation of data: (1) Guidelines for Food Matching, (2) Guidelines for Checking Food Composition Data prior to Publication of a User Table/Database, and (3) Guidelines for Converting Units, Denominators and Expressions. This article describes their content and development processes. Their adoption, along with additional ones planned for the future by FAO/INFOODS, should further improve the quality of published food composition data, which in turn can lead to more accurate nutrient intake estimates and more precise food labels, as well as better-targeted programs and policies.

Increasing fruit and vegetable consumption among schoolchildren: efforts in middle-income countries.

BACKGROUND: To reverse the trend of rising child obesity rates in many middle-income countries, recommendations include increasing fruit and vegetable consumption. Schools can positively impact children's eating behavior, and multicomponent interventions that include the curriculum, school food environments, and parental involvement are most effective. OBJECTIVE: To find out how fruits and vegetables feature in the dietary guidelines provided to schools, what specific schemes are available for providing these foods, the extent to which nutrition education is included in the curriculum, and how vegetables and fruits are procured in primary schools. METHODS: In 2008, a survey questionnaire previously validated and revised was sent electronically to national program managers and focal points for school feeding programs in 58 middle-income countries. The rationale was to obtain information relevant to the entire country from these key informants. The survey response rate was 46%. The information provided by 22 respondents in 18 countries was included in the current study. On average, respondents answered 88% of the questions analyzed in this paper. Of the respondents, 73% worked for the national authority responsible for school food programs, with 45% at the program coordinator or director level. RESULTS: Few countries have any special fruit and vegetable schemes; implementation constraints include cost and lack of storage facilities. Although 11 of 18 countries have both nutrient-based guidelines and school food guidelines for meals, fruits and vegetables are often not adequately specified. CONCLUSIONS: In some countries, nutrition education, special activities, school gardens, and parental participation are used to promote fruits and vegetables. Specific schemes are needed in some, together with school food guidelines that include fruits and vegetables.

Protein quality evaluation twenty years after the introduction of the protein digestibility corrected amino acid score method.

In 1989 the Joint FAO/WHO Expert Consultation on Protein Quality Evaluation recommended the use of the Protein Digestibility Corrected Amino Acid Score (PDCAAS) method for evaluating protein quality. In calculating PDCAAS, the limiting amino acid score (i.e., ratio of first limiting amino acid in a gram of target food to that in a reference protein or requirement) is multiplied by protein digestibility. The PDCAAS method has now been in use for 20 years. Research emerging during this time has provided useful data on various aspects of protein quality evaluation that has made a review of the current methods used in assessing protein quality necessary. This paper provides an overview of the use of the PDCAAS method as compared to other methods and addresses some of the key challenges that remain in regards to protein quality evaluation. Furthermore, specific factors influencing protein quality including the effects of processing conditions and preparation methods are presented. Protein quality evaluation methods and recommended protein intakes currently used in different countries vis-à-vis the WHO/FAO/UNU standards are further provided. As foods are frequently consumed in complement with other foods, the significance of the PDCAAS of single protein sources may not be evident, thus, protein quality of some key food groups and challenges surrounding the calculation of the amino acid score for dietary protein mixtures are further discussed. As results from new research emerge, recommendations may need to be updated or revised to maintain relevance of methods used in calculating protein quality.

Composition of milk from minor dairy animals and buffalo breeds: a biodiversity perspective.

A comprehensive review is presented of the nutrient composition for buffalo, mare, and dromedary camel milks at the level of breed, and species-level data for yak, mithun, musk ox, donkey, Bactrian camel, llama, alpaca, reindeer and moose milks. Average values of nutrients were calculated and compared. Interspecies values (g 100 g⁻¹) were 0.7-16.1 for total fat, 1.6-10.5 for protein, 2.6-6.6 for lactose, and 67.9-90.8 for water. Reindeer and moose milks had the highest fat and protein concentrations and the lowest lactose contents. Mare and donkey milks had the lowest protein and fat contents, in addition to showing the most appropriate fatty acid profile for human nutrition. Dromedary camel milk was most similar to cow milk in proximate composition. Moose milk was the richest in minerals, having values as high as 358 mg 100 g⁻¹ for calcium, 158 mg 100 g⁻¹ for sodium and 150 mg 100 g⁻¹ for phosphorus. Interbreed differences of 4 g 100 g⁻¹ were observed in total fat in buffalo, yak, mare and dromedary camel milks. Large interbreed differences were also present in the mineral contents in mare, buffalo and dromedary camel milks. By bringing together these compositional data, we hope to usefully widen the biodiversity knowledge base, which may contribute to the conservation and sustainable use of milk from underutilized dairy breeds and species, and to improved food and nutrition security, particularly in developing countries.

The structural characteristics of nonspecific lipid transfer proteins explain their resistance to gastroduodenal proteolysis.

The structure and stability of the allergenic nonspecific lipid transfer protein (LTP) of peach were compared with the homologous LTP1 of barley and its liganded form LTP1b. All three proteins were resistant to gastric pepsinolysis and were only slowly digested at 1 to 2 out of 14 potential tryptic and chymotryptic cleavage sites under duodenal conditions. Peach LTP was initially cleaved at Tyr79-Lys80 and then at Arg39-Thr40 (a site lost in barley LTP1). Molecular dynamics simulations of the proteins under folded conditions showed that the backbone flexibility is limited, explaining the resistance to duodenal proteolysis. Arg39 and Lys80 side chains were more flexible in simulations of peach compared with barley LTP1. This may explain differences in the rates of cleavage observed experimentally for the two proteins and suggests that the flexibility of individual amino acid side chains could be important in determining preferred proteolytic cleavage sites. In order to understand resistance to pepsinolysis, proteins were characterized by NMR spectroscopy at pH 1.8. This showed that the helical regions of both proteins remain folded at this pH. NMR hydrogen exchange studies confirmed the rigidity of the structures at acidic pH, with barley LTP1 showing some regions with greater protection. Collectively, these data suggest that the rigidity of the LTP scaffold is responsible for their resistance to proteolysis. Gastroduodenal digestion conditions do not disrupt the 3D structure of peach LTP, explaining why LTPs retain their ability to bind IgE after digestion and hence their allergenic potential.

Partially folded forms of barley lipid transfer protein are more surface active.

Thermal and chemical modification of protein structures is known to affect their interfacial activity. We have looked in detail at the effect of heating on the structure and subsequently the surface properties of LTP1, a nonspecific lipid transfer protein from barley, both in the presence and in the absence of its lipid adduct. CD and NMR spectroscopy showed that some of the protein molecules refold back to the native state structure after being heated to 100 degrees C for 2 h. However, for a proportion of the molecules, the structure of the protein was irreversibly unfolded which resulted in an increase in surface activity irrespective of the presence of the lipid adduct. These molecules show an increase in surface activity, which is normally associated with an increase in molecular flexibility and surface hydrophobicity and is a property that has been shown to be highly sensitive to structural changes. This explains why thermal and chemical modification of LTP1 is important in optimizing the surface properties of the protein that are essential in diverse applications from biosensors to beer foam.

Surface properties are highly sensitive to small ph induced changes in the 3-D structure of alpha-lactalbumin.

The change in structure of bovine alpha-lactalbumin in environments of decreasing pH from pH 7 to pH 3 was followed using high-resolution NMR and hydrogen exchange studies. The effect of the changes in the structure on the surface properties of the protein was also measured. As the pH was decreased from pH 7 toward pH 2, at which alpha-lactalbumin adopts a molten globule state, a small but increasing proportion of the molecules in the sample partially unfold. There was on average a loss of tertiary structure and a change in the environment of the tryptophan residues. A significant proportion of the change measured by both circular dichroism spectroscopy and interfacial methods observed as the pH was decreased from pH 7 to pH 4 was found to be irreversible upon readjustment back to pH 7. These changes in the sample conferred an increase in surface hydrophobicity and affected the surface properties. The surface activity was found to be highest at pH 4. This was because the increasing flexibility and surface hydrophobicity of the molecule with decreasing pH was balanced by the simultaneous increase in net charge repulsion. This conclusion was also confirmed by measurements of surface shear rheology. Interestingly the interfacial dilatational rheology was highest at the isoelectric point, indicating the dominant role of the charge interaction in controlling this parameter.

Post-translational modification of barley LTP1b: the lipid adduct lies in the hydrophobic cavity and alters the protein dynamics.

NMR techniques have been used to characterise the effects of a lipid-like post-translational modification on barley lipid transfer protein (LTP1b). NMR chemical shift data indicate that the lipid-like molecule lies in the hydrophobic cavity of LTP1b, with Tyr 79 being displaced to accommodate the ligand in the cavity. The modified protein has a reduced level of backbone amide hydrogen exchange protection, presumably reflecting increased dynamics in the protein. This may result from a loosening of the protein structure and may explain the enhanced surface properties observed for LTP1b.

Heat treatment of bovine alpha-lactalbumin results in partially folded, disulfide bond shuffled states with enhanced surface activity.

Prolonged heating of holo bovine alpha-lactalbumin (BLA) at 80 degrees C in pH 7 phosphate buffer in the absence of a thiol initiator improves the surface activity of the protein at the air:water interface, as determined by surface tension measurements. Samples after 30, 60, and 120 min of heating were analyzed on cooling to room temperature. Size-exclusion chromatography shows sample heterogeneity that increases with the length of heating. After 120 min of heating monomeric, dimeric, and oligomeric forms of BLA are present, with aggregates formed from disulfide bond linked hydrolyzed protein fragments. NMR characterization at pH 7 in the presence of Ca2+ of the monomer species isolated from the sample heated for 120 min showed that it consisted of a mixture of refolded native protein and partially folded protein and that the partially folded protein species had spectral characteristics similar to those of the pH 2 molten globule state of the protein. Circular dichroism spectroscopy showed that the non-native species had approximately 40% of the alpha-helical content of the native state, but lacked persistent tertiary interactions. Proteomic analysis using thermolysin digestion of three predominant non-native monomeric forms isolated by high-pressure liquid chromatography indicated the presence of disulfide shuffled isomers, containing the non-native 61-73 disulfide bond. These partially folded, disulfide shuffled species are largely responsible for the pronounced improvement in surface activity of the protein on heating.

Characterization of the molten globule of human serum retinol-binding protein using NMR spectroscopy.

The molten globule state is a partially folded conformer of proteins that has been the focus of intense study for more than two decades. This non-native fluctuating conformation has been linked to protein-folding intermediates, to biological function, and more recently to precursors in amyloid fibril formation. The molten globule state of human serum retinol-binding protein (RBP) has been postulated previously to be involved in the mechanism of ligand release (Ptitsyn, O. B., et al. (1993) FEBS Lett. 317, 181-184). Conserved residues within RBP have been identified and proposed to be key to folding and stability, although a link to a molten globule state has not previously been shown (Greene, L. H., et al. (2003) FEBS Lett. 553, 39-44). In this work, a detailed characterization of the acid-induced molten globule of RBP is presented. Using stopped-flow fluorescence spectroscopy in the presence of 8-anilino-1-naphthalene sulfonic acid (ANS), we show that RBP populates a state with molten-globule-like characteristics early in refolding. To gain insight into the structural features of the molten globule of RBP, we have monitored the denaturant-induced unfolding of this ensemble using NMR spectroscopy. The transition at the level of individual residues is significantly more cooperative than that found previously for the archetypal molten globule, alpha-lactalbumin (alpha-LA); this difference may be due to a predominantly beta-sheet structure present in RBP in contrast to the alpha-helical nature of the alpha-LA molten globule.