Advantages and limitations of the methodological approaches used to study dietary shifts towards improved nutrition and sustainability

Plant-based and sustainable diet: A systematic review of its impact on obesity

The food system significantly affects the environment through land use, emissions from livestock, deforestation, and food waste. Diet sustainability considers the environmental effects of food production, distribution, and consumption. Animal products emit more greenhouse gases than plant-based foods, prompting a shift towards plant-focused diets for reduced emissions. Sustainable diets, like the EAT-Lancet model, prioritize plant-based foods, adjusting for regional eating habits. These diets aim to be both environmentally friendly and conducive to human health, addressing concerns like obesity and chronic diseases. Obesity is a major global health challenge, and its complex relationship with food production and consumption patterns calls for sustainable solutions to reduce pressure on ecosystems and promote healthier lifestyles. Tackling obesity requires holistic strategies that address not only individual health but also the broader environmental impacts of food systems. A systematic review examined the link between plant-based diets and obesity focusing on studies assessing Body Mass Index (BMI) and body fat assessment. Despite limited research, evidence suggests that adherence to a plant-based diet, particularly a healthy one, is associated with lower obesity rates. More longitudinal and intervention studies are necessary for a stronger consensus on the matter.

Greenhouse gas emissions in relation to micronutrient intake and implications of energy intake: a comparative analysis of different modeling approaches

BACKGROUND

Human diets account for 30% of greenhouse gas emissions (GHGE). Reporting dietary GHGE with or without energy standardization yields different outcomes, often resulting in conflicting conclusions regarding associations with micronutrient intake.

OBJECTIVES

This study aims to compare methods of reporting dietary GHGE, with and without consideration of energy intake, and their respective associations with micronutrient intake.

METHODS

Data were sourced from the Malmö Diet and Cancer Study, a cohort involving 25,970 participants. GHGE were estimated based on life cycle assessment data. The study explores different methods of reporting dietary climate impact: GHGE per day, GHGE per 1000 kcal, and with different energy adjustments. Association with micronutrient intake was modeled as daily intake and per 1000 kcal using linear regression models.

RESULTS

Diets with higher GHGE per day were associated with a higher daily intake of all 17 examined micronutrients. When energy was included in the model, the results for GHGE per 1000 kcal aligned well with those for GHGE per day. However, using GHGE per 1000 kcal generally showed that higher GHGE were linked to lower daily micronutrient intake. Different methods of adjusting for energy intake yielded estimates with varying directions and magnitudes of associations.

CONCLUSIONS

This study highlights the implications of energy intake when assessing the impact of dietary GHGE and demonstrates that the choice of GHGE modeling approach might have important consequences for the results and interpretation. The method of choice for modeling dietary GHGE in relation to micronutrient intake needs to be carefully considered in future studies.

A methodological framework for deriving the German food-based dietary guidelines 2024: Food groups, nutrient goals, and objective functions

BACKGROUND

For a growing number of food-based dietary guidelines (FBDGs), diet optimization is the tool of choice to account for the complex demands of healthy and sustainable diets. However, decisions about such optimization models' parameters are rarely reported nor systematically studied.

OBJECTIVES

The objectives were to develop a framework for (i) the formulation of decision variables based on a hierarchical food classification system; (ii) the mathematical form of the objective function; and (iii) approaches to incorporate nutrient goals.

METHODS

To answer objective (i), food groups from FoodEx2 levels 3-7 were applied as decision variables in a model using acceptability constraints (5th and 95th percentile for food intakes of German adults (n = 10,419)) and minimizing the deviation from the average observed dietary intakes. Building upon, to answer objectives (ii) and (iii), twelve models were run using decision variables from FoodEx2 level 3 (n = 255), applying either a linear or squared and a relative or absolute way to deviate from observed dietary intakes, and three different lists of nutrient goals (allNUT-DRV, incorporating all nutrient goals; modNUT-DRV excluding nutrients with limited data quality; modNUT-AR using average requirements where applicable instead of recommended intakes).

RESULTS

FoodEx2 food groups proved suitable as diet optimization decision variables. Regarding deviation, the largest differences were between the four different objective function types, e.g., in the linear-relative modNUT-DRV model, 46 food groups of the observed diet were changed to reach the model's goal, in linear-absolute 78 food groups, squared-relative 167, and squared-absolute 248. The nutrient goals were fulfilled in all models, but the number of binding nutrient constraints was highest in the linear-relative models (e.g. allNUT-DRV: 11 vs. 7 in linear-absolute).

CONCLUSION

Considering the various possibilities to operationalize dietary aspects in an optimization model, this study offers valuable contributions to a framework for developing FBDGs via diet optimization.

Multicriteria Measures to Assess the Sustainability of Diets: A Systematic Review

CONTEXT

Assessing the overall sustainability of a diet is a challenging undertaking requiring a holistic approach capable of addressing the multicriteria nature of this concept.

OBJECTIVE

The aim was to identify and summarize the multicriteria measures used to assess the sustainability characteristics of diets reported at the individual level by healthy adults.

DATA SOURCES

Articles were identified via PubMed, Scopus, and Web of Science. The search strategy consisted of key words and MeSH terms, and was concluded in September 2022, covering references in English, Spanish, and Portuguese.

DATA EXTRACTION

This systematic review followed the PRISMA guidelines. The search identified 5663 references, from which 1794 were duplicates. Two reviewers independently screened the titles and abstracts of each of the 3869 records and the full-text of the 144 references selected. Of these, 7 studies met the inclusion criteria.

DATA ANALYSIS

A total of 6 multicriteria measures were identified: 3 different Sustainable Diet Indices, the Quality Environmental Costs of Diet, the Quality Financial Costs of Diet, and the Environmental Impact of Diet. All of these incorporated a health/nutrition dimension, while the environmental and economic dimensions were the second and the third most integrated, respectively. A sociocultural sustainability dimension was included in only 1 of the measures.

CONCLUSION

Despite some methodological concerns in the development and validation process of the identified measures, their inclusion is considered indispensable in assessing the transition towards sustainable diets in future studies.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD42022358824.

Which dietary shifts to improve nutritional quality while reducing diet cost in the French West Indies?

BACKGROUND

The French West Indies are facing increasing rates of obesity and diet-related chronic diseases. Food prices are more than 30% higher compared with mainland France, while a large part of the population is socioeconomically disadvantaged. The affordability of a healthy diet is a key issue.

OBJECTIVE

To identify dietary shifts allowing to achieve nutritional adequacy while reducing the cost of Guadeloupean and Martinican adult diets.

METHODS

Dietary intakes of 1112 adults (≥ 16y) were obtained from a cross-sectional survey conducted on a representative sample of the Guadeloupean and Martinican populations. Diet cost was based on mean prices of 1357 foods compiled from a Martinican supermarket website. Individual optimized diets respecting all nutritional recommendations with minimized departure from the initial diet were designed under different scenarios of cost constraint: none, not exceeding the initial diet cost (COSTinit), and 10%-step reductions (COST-X%); the initial diet cost referring to the cost of the diet based on initial dietary intakes and mean food prices.

RESULTS

Without cost constraint, achieving nutritional adequacy while departing the least from initial diet increased diet cost on average (+ 20%) and for 74% of adults. In COSTinit, achieving nutritional adequacy was possible for 98% of adults and induced an increase in the amount of fruit & vegetables, unrefined starches, dairy products (especially milk), eggs and vegetable fats, and a decrease in sweetened beverages (especially among < 30y), refined cereals, sweetened products, meat and fish. In COST-30% scenario, achieving nutritional adequacy was possible for 93% of adults and induced the same dietary shifts as in COSTinit, but modified their magnitude, notably a smaller increase of vegetables (increase of + 7 g/d in the COST-30% scenario and + 86 g/d in the COSTinit scenario, both relative to initial diet), a larger increase of dairy (+ 90 g/d and + 72 g/d, respectively) and starchy foods (+ 112 g/d and + 54 g/d), and a larger reduction of meat (-48 g/d and -12 g/d). Increases in fruits (~ + 80 g/d) and unrefined starches (+ 127 g/d), and decreases in sweetened beverages (~ -100 g/d) and fish (~ -40 g/d) were maintained.

CONCLUSIONS

Nutrition prevention programs promoting the affordable and nutritious dietary shifts identified in the present study, i.e. reduction in animal flesh foods (meat, fish) as well as refined cereals and sweet products in favour of an increase in healthy plant-based foods and animal co-products (dairy, eggs), could help improve nutritional adequacy of the Guadeloupean and Martinican populations.

An overview of approaches for assessing the environmental sustainability of diets - a scoping review for Nordic Nutrition Recommendations 2023

Assessing the environmental impacts of food, food systems and diets is highly complex due to the multitude of processes involved, the uncertainty in assessment models, the variability in production systems and the large range of products available. No single assessment method alone can provide a complete evidence base. The increasing number of Life Cycle Assessment and food system analyses, and more recently the integration of planetary boundaries offer insights from which we can draw some robust high-level conclusions, whilst recognising there is a need for more detailed analysis to capture the inherent nuances of more location and context-specific situations. Despite the complexity of assessing the environmental sustainability of food, diets and food systems, there are a number of key considerations that could be used to guide this process, and in doing so, they help to increase utility of the outcomes and limit unintended adverse consequences. We identified five key considerations that can be applied (consider the thresholds, consider the system, consider the variables, consider the context and consider the spillover) to ensure assessments are comprehensive.

Can micronutrient requirements be met by diets from sustainable sources: outcomes of dietary modelling studies using diet optimization

BACKGROUND

Consumption of diets from sustainable sources is required for planetary health, however, large sections of the population, including females of reproductive age and children, will be at risk of not meeting their micronutrient (MN) requirements in a complete transition to plant-based foods. Constrained diet optimization methods use mathematical programming to construct diets that meet predefined parameters and may contribute towards modelling dietary solutions that meet nutritional and planetary targets.

OBJECTIVE

Review the evidence from diet optimization studies proposing solutions to ensure MN availability in the context of a transition to diets from sustainable sources.

APPROACH

Narrative review focusing on literature published over the last five years.

RESULTS

Dietary modelling using diet optimization can design a range of omnivorous and plant-based diets that meet individual MN requirements, have reduced environmental impacts, and minimize deviation from culturally acceptable dietary practices. Using data from large-scale dietary surveys, diet optimization can support development of food-based dietary guidelines; identify limiting MNs in a particular context or a conflict between constraints e.g. nutrition and environment; explore food-based strategies to increase nutrient supply, such as fortification; and support trial design. Methods used and outcomes reported are sources of variability. Individual-level dietary data and MN requirements for population sub-groups such as females of reproductive age and children are important requirements. Although maintaining iron and zinc intakes are regularly reported to present challenges in diets from sustainable sources, few studies have considered bioavailability, which reduces with increased dietary phytate. These and other data gaps including acceptability and affordability must be addressed to improve the applicability of modelling outcomes in population recommendations.

CONCLUSIONS

Dietary modelling using diet optimization can be useful in the design of more sustainable diets that meet MN requirements, however, translation of outcomes into dietary intervention studies is required to test real-world application and adoption into dietary guidelines.

Low-carbon diets across diverse dietary patterns: Addressing population heterogeneity under constrained optimization

Mathematical optimization is a useful tool for modeling diets that fulfill requirements for health and environmental sustainability, however, population-based optimization approaches fail to account for underlying dietary diversity in populations. This study proposes a methodological approach to consider diverse dietary intake patterns in mathematical optimization of nutritionally adequate low-carbon diets and investigates the differences between different population groups, along with trade-offs between greenhouse gas emission (GHGE) reduction and the inconvenience of dietary changes required to achieve optimized diets. A k-means clustering analysis was applied to individual dietary intake data from Denmark, which resulted in four clusters with different dietary patterns. This was followed by quadratic programming, wherein the total dietary changes required from the observed diet within each cluster were used as a proxy for consumer inconvenience (i.e., "inconvenience index") and were minimized while fulfilling nutrient constraints and incrementally tightened GHGE constraints. Across clusters, a steep increase of the inconvenience index was observed at GHGE levels below approximately 3 kg CO2e/10 MJ, corresponding to GHGE reductions of 24-36 % in different clusters. In all clusters, the optimized diets with nutritional and GHGE constraints showed common traits of increased content of cereals and starches, eggs, and fish and decreased amounts of beef and lamb, cheese, animal-based fats, and alcoholic beverages, but differences across clusters were also observed, maintaining characteristics of the clusters' baselines. When additional health-based targets for food amounts were applied as constraints, the optimized diets converged towards the same type of diet. The total inconvenience of dietary changes required to fulfill constraints differed between clusters, indicating that specific sub-populations may be more effective targets for dietary transition. The method has potential for future integration of more sustainability aspects and different consumer preferences.

Integrating environmental sustainability into food-based dietary guidelines in the Nordic countries

The overall aim of this paper was to provide background knowledge to the Nordic Nutrition Recommendations 2023 Committee for integrating environmental sustainability in a framework for national Food-Based Dietary Guidelines (FBDG) within the Nordics and Baltics. Additionally, this paper aims to give an overview of recent Nordic scientific literature on environmental impact of foods and dietary patterns and of the FBDG of the Nordics. Finally, we suggest methods for developing national sustainable FBDG. Nordic and Baltic studies on sustainability of diets were searched in August 2022 and complemented with additional relevant literature. The studies show that current diets are far from environmentally sustainable, exceeding planetary boundaries for most impact categories; meat and dairy products being the largest contributors to dietary greenhouse gas emissions (GHGEs) and land use. Scenario, modelling, optimisation and intervention studies confirm the potential of shifting towards more plant-based diets to improve overall diet quality in terms of both health and environmental sustainability. Such diets comprised of vegetables, fruits, legumes, potatoes, whole grain and refined cereal products, nuts, seeds and vegetable oils, with animal foods in moderate or limited amounts. The FBDG in the Nordics promotes more plant-based diets than the current average diet but could improve from further integration of environmental sustainability. To form basis for sustainable FBDG dietary modelling at the national level, prioritising health outcomes and nutritional adequacy is essential. Second, integrating environmental sustainability involves estimating the impact of food choices and amounts on GHGE, land and water use, eutrophication and biodiversity loss. Exploring positive and negative implications of fortified foods and supplementation in relation to nutrient intake, health and environmental sustainability may be needed. Implementing dietary transition requires solutions beyond FBDG to ensure affordability, acceptability and ease of adaption.

Exploring tradeoffs among diet quality and environmental impacts in self-selected diets: a population-based study

PURPOSE

Proposed sustainable diets often deviate dramatically from currently consumed diets, excluding or drastically reducing entire food groups. Moreover, their environmental sustainability tends to be measured only in terms of greenhouse gases emissions. The aim of this study was to overcome these limitations and identify a cluster of already adopted, relatively healthy diets with substantially lower environmental impacts than the average diet. We also aimed to estimate the reduction in multiple environmental impacts that could be achieved by shifting to this diet cluster and highlight possible tradeoffs among environmental impacts.

METHODS

The diet clusters were identified by applying energy-adjusted multiple factor analysis and hierarchical clustering to the dietary data of the National FinHealth 2017 Study (n = 5125) harmonized with life cycle assessment data on food products from Agribalyse 3.0 and Agri-Footprint using nutrient intakes and global warming potential, land use, and eutrophication of marine and freshwater systems as the active variables.

RESULTS

We identified five diet clusters, none of which had the highest overall diet quality and lowest impact for all four environmental indicators. One cluster, including twenty percent of the individuals in the sample was identified as a "best compromise" diet with the highest diet quality and the second lowest environmental impacts of all clusters, except for freshwater eutrophication. The cluster did not exclude any food groups, but included more fruits, vegetables, and fish and less of all other animal-source foods than average. Shifting to this cluster diet could raise diet quality while achieving significant reductions in most but not all environmental impacts.

CONCLUSION

There are tradeoffs among the environmental impacts of diets. Thus, future dietary analyses should consider multiple sustainability indicators simultaneously. Cluster analysis is a useful tool to help design tailored, socio-culturally acceptable dietary transition paths towards high diet quality and lower environmental impact.

Impact of consuming an environmentally protective diet on micronutrients: a systematic literature review

BACKGROUND

A global move toward consumption of diets from sustainable sources is required to protect planetary health. As this dietary transition will result in greater reliance on plant-based protein sources, the impact on micronutrient (MN) intakes and status is unknown.

OBJECTIVE

Evaluate the evidence of effects on intakes and status of selected MNs resulting from changes in dietary intakes to reduce environmental impact. Selected MNs of public health concern were vitamins A, D, and B12, folate, calcium, iron, iodine, and zinc.

METHODS

We systematically searched 7 databases from January 2011 to October 2022 and followed the PRISMA guidelines. Eligible studies had to report individual MN intake and/or status data collected in free-living individuals from the year 2000 onward and environmental outcomes.

RESULTS

From the 10,965 studies identified, 56 studies were included, mostly from high-income countries (n = 49). Iron (all 56) and iodine (n = 20) were the most and least reported MNs, respectively. There was one randomized controlled trial (RCT) that also provided the only biomarker data, 10 dietary intake studies, and 45 dietary modeling studies, including 29 diet optimization studies. Most studies sought to reduce greenhouse gas emissions or intake of animal-sourced foods. Most results suggested that intakes of zinc, calcium, iodine, and vitamins B12, A, and D would decrease, and total iron and folate would increase in a dietary transition to reduce environmental impacts. Risk of inadequate intakes of zinc, calcium, vitamins A, B12 and D were more likely to increase in the 10 studies that reported nutrient adequacy. Diet optimization (n = 29) demonstrated that meeting nutritional and environmental targets is technically feasible, although acceptability is not guaranteed.

CONCLUSIONS

Lower intakes and status of MNs of public health concern are a potential outcome of dietary changes to reduce environmental impacts. Adequate consideration of context and nutritional requirements is required to develop evidence-based recommendations. This study was registered prospectively with PROSPERO (CRD42021239713).

Reducing the carbon footprint of diets across socio-demographic groups in Finland: a mathematical optimisation study

OBJECTIVES

To characterise nutritionally adequate, climate-friendly diets that are culturally acceptable across socio-demographic groups. To identify potential equity issues linked to more climate-friendly and nutritionally adequate dietary changes.

DESIGN

An optimisation model minimises distance from observed diets subject to nutritional, greenhouse gas emissions (GHGE) and food-habit constraints. It is calibrated to socio-demographic groups differentiated by sex, education and income levels using dietary intake data. The environmental coefficients are derived from life cycle analysis and an environmentally extended input-output model.

SETTING

Finland.

PARTICIPANTS

Adult population.

RESULTS

Across all population groups, we find large synergies between improvements in nutritional adequacy and reductions in GHGE, set at one-third or half of the current level. Those reductions result mainly from the substitution of meat with cereals, potatoes and roots and the intra-category substitution of foods, such as beef with poultry in the meat category. The simulated more climate-friendly diets are thus flexitarian. Moving towards reduced-impact diets would not create major inadequacies related to protein and fatty acid intakes, but Fe could be an issue for pre-menopausal females. The initial socio-economic gradient in the GHGE of diets is small, and the patterns of adjustments to more climate-friendly diets are similar across socio-demographic groups.

CONCLUSIONS

A one-third reduction in GHGE of diets is achievable through moderate behavioural adjustments, but achieving larger reductions may be difficult. The required changes are similar across socio-demographic groups and do not raise equity issues. A population-wide policy to promote behavioural change for diet sustainability would be appropriate.

Consumer attitudes and behaviors toward more sustainable diets: a scoping review

There is an urgent need to move toward more sustainable diets. Although this will require radical and systemic changes across food systems, altering consumer ideologies and practices is essential to garner support for such actions. In this scoping review, the evidence on consumers' attitudes and behaviors toward more sustainable diets is synthesized and a range of factors, considerations, and proposed strategies are presented that can contribute to building the societal-level support for urgent and systems-level changes. The findings suggest that consumers, insofar as they are interested in sustainability and have the capacity to engage with the concept, primarily approach the concept of sustainable diet from a human health perspective. However, the interconnectedness of human health and well-being with environmental health is poorly understood and under-researched in the context of consumer behaviors and attitudes toward sustainable diets. This highlights the need for (1) sustained efforts from public health professionals to encourage a realignment of the term sustainable diet with its multidimensional meaning by championing an ecological public health approach in all efforts aimed at promoting more sustainable consumption, from awareness raising to policy development; (2) a broader research lens focused on the multidimensional concept of sustainability in the literature exploring consumer attitudes and behaviors; and (3) the development of multidisciplinary, clear, and evidence-based sustainable-eating messages, including holistic sustainable dietary guidance, to address knowledge gaps, minimize conflicting narratives, and build consumer agency. The findings contribute to understanding how support can be generated for the necessary structural and system-level changes required to support behavior change.

Exploring Benefits and Barriers of Plant-Based Diets: Health, Environmental Impact, Food Accessibility and Acceptability

Unhealthy dietary patterns are directly linked to the current Global Syndemic consisting of non-communicable diseases, undernutrition and climate change. The dietary shift towards healthier and more sustainable plant-based diets is essential. However, plant-based diets have wide intra differences; varying from vegan diets that totally exclude meat and animal products to traditional ones such as the Mediterranean diet and the new Nordic diet. It is acknowledged that plant-based diets may contribute simultaneously to improving population health as well as to decreasing the environmental impact of food systems. Evidence from cohort and randomized-controlled trials suggests that plant-based dietary patterns have beneficial effects on bodyweight control, cardiovascular health and diabetes prevention and treatment. On the other hand, micronutrient requirements may not be met, if some plant-based diets are not well-planned. Additionally, studies showed that lower consumption of meat and animal products results in lower environmental impacts. Consequently, plant-based diets could be a key factor to increase diet sustainability. This narrative review addresses the advantages of adherence to plant-based diets on human and planetary health considering strains and barriers to achieve this dietary transition, including cultural acceptability and affordability factors. Finally, potential intervention and policy recommendations are proposed, focusing on the update of current national food-based dietary guidelines.

Dietary Greenhouse Gas Emissions and Diet Quality in a Cross-Sectional Study of Swedish Adolescents

BACKGROUND

Interventions to improve dietary intake and reduce dietary greenhouse gas emissions (dGHGE) are urgently needed. Adolescence presents a unique time in life to promote sustainable diets. Detailed dietary data are needed to inform public health strategies aiming at improving adolescents' diet quality and reducing dGHGE.

OBJECTIVE

This study aimed to describe dGHGE in Swedish adolescents' diets by socio-demographic characteristics, evaluate how food groups contribute to dGHGE, and examine dGHGE in relation to diet quality.

METHODS

Data come from the national, school-based, cross-sectional dietary survey Riksmaten Adolescents 2016-17 of 3099 females and males attending school grades 5 (11-12 y old), 8 (14-15 y old) and 11 (17-18 y old). Participants completed 2 web-based 24-h recalls and questionnaires on lifestyle factors. dGHGE was estimated based on life cycle assessment data. Diet quality was estimated using NRF11.3 (Nutrient Rich Food Index) and SHEIA15 (Swedish Healthy Eating Index for Adolescents 2015).

RESULTS

dGHGE were higher in males than females (medians 4.2 versus 3.8 kg CO2e/10 MJ, P < 0.001). In females, dGHGE were highest in grade 5 (4.0 kg CO2e/10MJ), whereas in males, emissions were highest in grade 11 (4.4 kg CO2e/10MJ), P < 0.001 for the sex/grade interaction. Overweight/obesity was positively associated with CO2e/10MJ, but parental education, birthplace, and degree of urbanization were not. In females, the proportion of dGHGE from animal-based foods was lowest in grade 11, whereas the proportions from plant-based foods and sweet foods/beverages were highest. In males, these proportions were similar across grades. NRF11.3 was not associated with CO2e/10MJ, whereas healthier eating, according to SHEIA15, was inversely associated with CO2e/10MJ.

CONCLUSIONS

Food choices and dGHGE per calorie differ by sex in adolescents. Thus, intervention strategies to improve dietary sustainability need to be tailored differently to females and males. Diet quality should also be considered when promoting reduced GHGE diets.

The nutrition and immunity (nutrIMM) study: protocol for a non-randomized, four-arm parallel-group, controlled feeding trial investigating immune function in obesity and type 2 diabetes

Introduction

Individuals with obesity and/or type 2 diabetes are at higher risk of infection and have worse prognoses compared to healthy individuals. Several factors may influence immune responses in this population, including high adiposity, hyperglycemia, and unhealthy dietary habits. However, there is insufficient data on the independent or clustered contribution of these factors to obesity-related immune dysfunction, especially accounting for dietary intake. This study aims to establish the independent contribution of obesity and hyperglycemia to immune dysfunction independent of diet in adults with and without obesity with or without type 2 diabetes.

Methods

The Nutrition and Immunity (nutrIMM) study is a single-centre, non-randomized, four-arm, parallel-group, controlled feeding trial. It will enroll adults without obesity (Lean-NG) and with obesity and three metabolic phenotypes of normoglycemia, glucose intolerance, and type 2 diabetes. Participants will be assigned to one of four groups and will consume a standard North American-type diet for 4 weeks. The primary outcomes are plasma concentration of C-reactive protein and concentration of ex-vivo interleukin-2 secreted upon stimulation of T cells with phytohemagglutinin.

Discussion

This will be the first controlled feeding study examining the contribution of obesity, hyperglycemia, and diet on systemic inflammation, immune cell phenotype, and function in adults of both sexes. Results of this clinical trial can ultimately be used to develop personalized dietary strategies to optimize immune function in individuals with obesity with different immune and metabolic profiles.

Clinical trial registration

ClinicalTrials.gov, identifier NCT04291391.

Exploring healthy and climate-friendly diets for Danish adults: an optimization study using quadratic programming

Background

A transition to healthy and sustainable diets has the potential to improve human and planetary health but diets need to meet requirements for nutritional adequacy, health, environmental targets, and be acceptable to consumers.

Objective

The objective of this study was to derive a nutritionally adequate and healthy diet that has the least deviation possible from the average observed diet of Danish adults while aiming for a greenhouse gas emission (GHGE) reduction of 31%, corresponding to the GHGE level of the Danish plant-rich diet, which lays the foundation for the current healthy and sustainable food-based dietary guidelines (FBDGs) in Denmark.

Methods

With an objective function minimizing the departure from the average observed diet of Danish adults, four diet optimizations were run using quadratic programming, with different combinations of diet constraints: (1) nutrients only (Nutri), (2) nutrients and health-based targets for food amounts (NutriHealth), (3) GHGE only (GHGE), and finally, (4) combined nutrient, health and GHGE constraints (NutriHealthGHGE).

Results

The GHGE of the four optimized diets were 3.93 kg CO₂-eq (Nutri), 3.77 kg CO₂-eq (NutriHealth) and 3.01 kg CO₂-eq (GHGE and NutriHealthGHGE), compared to 4.37 kg CO₂-eq in the observed diet. The proportion of energy from animal-based foods was 21%-25% in the optimized diets compared to 34% in the observed diet and 18% in the Danish plant-rich diet. Moreover, compared to the average Danish diet, the NutriHealthGHGE diet contained more grains and starches (44 E% vs. 28 E%), nuts (+230%), fatty fish (+89%), eggs (+47%); less cheese (-73%), animal-based fats (-76%), total meat (-42%); and very limited amounts of ruminant meat, soft drinks, and alcoholic beverages (all-90%), while the amounts of legumes and seeds were unchanged. On average, the mathematically optimized NutriHealthGHGE diet showed a smaller deviation from the average Danish diet compared to the Danish plant-rich diet (38% vs. 169%, respectively).

Conclusion

The final optimized diet presented in this study represents an alternative way of composing a nutritionally adequate and healthy diet that has the same estimated GHGE as a diet consistent with the climate-friendly FBDGs in Denmark. As this optimized diet may be more acceptable for some consumers, it might help to facilitate the transition toward more healthy and sustainable diets in the Danish population.

The Alignment of Recommendations of Dietary Guidelines with Sustainability Aspects: Lessons Learned from Italy's Example and Proposals for Future Development

The main objective of this paper is to describe the process of the inclusion of sustainability in the Italian Dietary Guidelines (IDGs). In the IDGs' sustainability chapter, particular emphasis was put on the selection of foods, recommending a plant-based diet with a large quota of vegetable proteins. Advice was also given on the selection of local seasonal products, with low growth input, such as fertilizers, artificial light and heating. Reduction of animal food was recommended, to be substituted with lower impact foods (poultry, milk, eggs and Mediterranean fish including aquaculture). Food waste was largely addressed. Recommendations were made for food purchase planning, food storage and the reuse of leftovers as strategies to reduce waste and save money. The IDGs sustainability recommendations were related to the 16 guiding principles of a sustainable healthy diet and their contribution to the achievement of the Sustainable Developing Goals was provided. The inclusion of sustainability in dietary guidelines requires a multidisciplinary approach to cover the wide range of aspects of a sustainable diet. In the IDGs, it was possible to show that practical recommendations for improving sustainability behavior can be passed on to consumers. Methodological aspects for developing recommendations are not definitive.