The multilevel dimensions of sustainable diets associating food systems, public health, environmental sustainability, and culture are presented in this paper. It begins by defining sustainable diets as those that are healthful, have low environmental impacts, are affordable, and culturally acceptable. The discussion includes the history of research on sustainable diets, from initial studies focused on environmental impacts to more recent, comprehensive frameworks that integrate affordability, cultural relevance, and nutritional adequacy as key dimensions of diet sustainability. In addition, the paper highlights recent innovations, such as the Planetary Health Diet of EAT–Lancet and the SHARP model, and the conflicts and optimum trade-offs between sustainability and nutrition, particularly within low- and middle-income countries. Case descriptions of Mediterranean Diet with a focus on Traditional Lebanese Diet, and African Indigenous Foods demonstrate culturally confined dietary patterns associated with sustainability objectives. These examples show that sustainable diets are not a single set of prescriptions, but a series of multiple pathways that are shaped by local food environments, ecological belts, and sociocultural heritages. The paper also describes major policy and governance activities necessary to promote sustainable diets. Finally, the paper addresses measurement challenges and advocates for better indicator options to measure sustainable food systems in all their facets and for participatory and context-specific approaches. The discussion concludes that fairer and culturally diverse inclusion strategies, system change, and political determination are imperative in achieving sustainable diets. Diets able to sustain are posited as agents capable of driving the 2030 agenda, enhancing planetary health and social integrity.

Carbon labelling has been proposed as a strategy to encourage cafeteria diners to reduce meat consumption, choose lower carbon-emitting meals and contribute towards global climate change targets. However, field-experimental evidence for label effectiveness is largely limited to trials in universities with student samples. This study evaluated whether the beneficial effects of carbon labelling observed in universities could be replicated in the wider workplace population through a natural field experiment in four call-centre cafeterias in Northern England. Baseline vegetarian uptake in the call-centre cafeterias was significantly lower than in previous university trials (7% vs 15–66%), potentially reflecting a more meat-attached population. The introduction of labels resulted in a 1.5 percentage-point shift from meat to vegetarian meals compared to 1.7–4.6 percentage-point shifts observed in university trials. The increase was almost entirely driven by higher vegetarian sales during the first week of the intervention, with little to no effect observed in subsequent weeks. No statistically significant changes were found in average cafeteria emissions. The findings suggest that carbon labels are not a panacea, and where worksite cafeterias have ambitious emissions targets, labels will need to be implemented alongside other measures.

This study explored whether lifestyle therapy that promoted adherence to a Mediterranean-style diet as a treatment for depression led to environmental co-benefits. Participants (n 75 complete case) were Australian adults in the Curbing Anxiety and Depression using Lifestyle Medicine non-inferiority, randomised controlled trial, which showed that lifestyle therapy was non-inferior to psychotherapy in reducing depressive symptoms, when delivered in group format via video conferencing over an 8-week treatment period. In this secondary analysis, we hypothesised that the lifestyle arm would be superior to the psychotherapy arm in reducing the environmental impact of self-reported diet over time. Dietary intake derived from FFQ at baseline and 8 weeks was transformed into environmental impact scores by calculating global warming potential (GWP)*. GWP* was calculated for total dietary intake and distinct food groups (Australian Dietary Guidelines and NOVA classifications). Within-arm changes in GWP* over time were calculated using the median difference. Neither arm showed significant changes. Between-arm differences in percentage change in GWP* scores over time were analysed using generalised estimating equations models. No between-arm difference for total GWP* score was found (β = 11·06 (–7·04, 29·15)). When examining distinct food groups, results were mixed. These novel findings contribute to the sparse evidence base that has measured the environmental impact of diets in a clinical trial context. Whilst lifestyle therapy that reduced depressive symptoms did not have clear environmental benefits relative to psychotherapy, nutritional counselling that focuses on the environmental impact of food choices may drive more pronounced planetary co-benefits.

In recognition of the impact of current dietary patterns on human and environmental health, dietary shifts towards sustainable diets are considered crucial to adequately feed a growing global population within planetary boundaries. Whilst the composition of sustainable diets varies to account for regional specificity, consensus exists on the need to reduce meat and increase plant protein intakes in sustainable dietary patterns for high-income settings. Due to the high environmental impact resulting from meat production and observational evidence of higher risks of negatives health outcomes associated with excess red and processed meat, a reduction in meat consumption is considered a ‘win-win’ for both people and the planet. However, meat is an important contributor to dietary protein and micronutrient intakes and plays an important sociocultural role, particularly in the UK and Ireland. Whilst a strong evidence-base exists on the environmental and health benefits associated with increased consumption of whole plant foods such as legumes, nuts and seeds, these foods may not address the barriers associated with lower meat diets. Plant-based meat alternatives (PBMAs) are products created to replicate the taste, texture, appearance and functionality of meat and therefore may provide an acceptable means of facilitating the shift to healthy and more sustainable diets. However, less is known about the health and environmental impact of substituting meat with PBMAs. Therefore, this review summarises the literature on the nutritional, health and environmental impact of PBMAs to better understand the role of these products in healthy and sustainable diets for the UK and Ireland.

Sustainable diets should promote good health for both the planet and the individual. While there is a clear association between lower environmental impact diets and better health outcomes, intervention studies are needed to determine the range of dietary changes and to understand inter-individual differences in response. Individuals having different responses to dietary interventions are underpinned by a variety of genetic, phenotypic and behavioural factors. The aim of this review is to apply the findings from previous literature examining inter-individual variation and phenotypic response to the future of sustainable healthy diets. Despite changing diets or improving diet quality, physiological responses are varied in randomised controlled trials. To better understand response, individuals can be grouped based on shared baseline characteristics or by their shared response to an intervention. Studies grouping individuals by shared characteristics use a metabolic phenotyping or metabotyping approach which demonstrates that some phenotypes are more predisposed to respond to a particular intervention. Tailoring dietary advice to metabolic phenotype shows promise for improving health and diet quality. However, more evidence is needed to understand the complexity that will come with whole dietary change in the context of sustainable healthy diets. We envisage a future where metabolic phenotyping is an integral element for prescribing personalised nutrition advice for sustainable healthy diets.

This cross-sectional study examined the barriers and facilitators that influence vegetarian menu choices in a university cafeteria in Geneva, Switzerland. As a first step, an online survey developed by the authors based on the Capability, Opportunity, and Motivation Behaviour (COM-B) model was e-mailed to all university students and staff. In the second step, focus groups (FG) were held to complete the survey responses and identify what needed to be changed to promote the choice of the vegetarian menu in the cafeteria. Data from 304 participants collected through the survey was analysed. The main mentioned barriers were lack of vegetarian options, tastelessness and insufficient satiation. The facilitators that emerged from the survey were the price of the vegetarian menu for students and health and environmental benefits. Thirteen people participated in four FG sessions, which were analysed using thematic analysis. Five themes were identified: spontaneous menu selection, predefined menu selection, influence of opportunity on menu selection, influence of environmental sensitivity on menu selection, and threat to identity in menu selection. The choice of a vegetarian menu in a university cafeteria was mainly influenced by the attractiveness and taste of the plate. Future strategies to reduce food-related greenhouse gas emissions should (a) ensure the quality and attractiveness of the vegetarian menu, especially to appeal to the more resistant, such as men and omnivores, and (b) inform consumers about the guarantee of balanced nutrient intake of the vegetarian menu offered in the cafeteria, and about health and environmental benefits.

Adolescence is an important life-stage during which shifts towards more healthy and sustainable diets can be promoted. Adolescents have increasing influence over their food choices informed by their developing personal knowledge and values, impacting long-term dietary behaviours into adulthood(1). We aimed to review the recent literature regarding adolescents’ perceptions of environmentally sustainable diets, and interventions to support adolescents to eat sustainably. We reviewed published literature that focussed on adolescent participants and their perceptions of, or interventions to support, sustainable dietary habits. Five electronic databases were searched to include studies published since 2012 that met the inclusion criteria. The JBI approach and PRISMA-Sc checklist(2) was used for source screening, data extraction and presentation of data. Data was extracted including study characteristics, methodology and results in relation to each research question. The extracted data was reported, synthesised and discussed in the context of the food system framework(3) and broader research. Twenty-eight articles were included in the review. Findings suggest that adolescents’ understanding of what constitutes sustainable eating is low. Most adolescents, when asked, were unsure of what constitutes sustainable eating, or a plant-based diet. The environmental impact of the production methods, transport and packaging of foods was most commonly reported when adolescents considered the environmental impact of their foods. The most commonly perceived barrier to consuming sustainable foods mentioned was cost, particularly by adolescents from lower socioeconomic backgrounds. Other barriers include unappealing taste, appearance or smell of ‘sustainable’ food items (particularly those that were vegetarian). Geographical limitations impacting the ability to grow or purchase local and organic products were also mentioned as barriers to consuming sustainable foods. Adolescents reported a lack of understanding of sustainable diets, and distrust of sustainability-related claims from fast-food outlets regarding the quality or source of ingredients, making it difficult to make informed food choices. Additionally, behaviours conflicting with personal and/or group norms were noted as barriers to adopting sustainable dietary habits. Adolescents that had previously received relevant education, valued nature and health, or were from a rural or indigenous community, were more likely to value environmentally sustainable food choices. Interventions which target adolescents’ cognitive understanding and aspiration to make sustainable food choices appear to improve their attitudes towards sustainable food, whereas interventions to increase the availability of sustainable foods improved the environmental sustainability of adolescents’ dietary intake. Multicomponent, tailored and community-based interventions were most effective however the long-term effect of these interventions remains unclear. More research is needed in diverse countries and settings, with consideration of adolescents’ level of autonomy in food choice and long term-effectiveness of interventions.

Based on the World Health Organization’s definition(1), sustainable healthy diets are “dietary patterns that promote all dimensions of an individuals’ health and well-being; have low environmental pressure and impact; are accessible, affordable, safe and equitable; and are culturally acceptable”. Over the past decade, there has been an increasing interest in the environmental sustainability of diets, but little attention has been paid to the nutrient adequacy, consumer acceptability and affordability of such diets. Such knowledge is particularly scarce in New Zealand where approximately 40% of adults and 20% of children may live under severe to moderate food insecurity(2,3). The iOTA Model® is a dietary optimisation tool designed to fill this gap by bringing the various aspects of diet sustainability together and providing evidence-based knowledge on not just the environmental impact of food but also its economic and nutritional sustainability at a national level. The iOTA Model® was constructed using mixed integer linear programming by integrating New Zealand-specific dietary data. This underlying data was obtained from various open-access sources including but not limited to New Zealand’s Food Composition Database, New Zealand Total Diet Study and the nutrient reference values published by the Ministry of Health. Diet-related greenhouse gas emissions were also incorporated into the model based on the data obtained from the scientific literature. Results derived from the preliminary development of the iOTA Model® suggest that meeting nutrient adequacy is possible with minimal dietary pattern changes in New Zealand. It is also evident that adhering to dietary guidelines may provide 26% reduction in dietary greenhouse gas emissions. This is consistent with the findings of previous studies showing that following dietary guidelines alone assists reduction of dietary greenhouse gas emissions. Further features such as digestibility and bioavailability considerations have also been incorporated as part of the iOTA Model®, allowing for a more accurate estimation of nutrient supply. The model will be available as an open-access tool and will allow users to explore various sustainability implications of their diet.

The objective of this study was to describe changes in sustainable dietary behaviours (those that support environmental, economic, and physical health) among a sample of US adults during the COVID-19 pandemic and to examine differences in changes by individuals’ race/ethnicity and socioeconomic status. Therefore, a cross-sectional online survey study was conducted in April 2021 (N = 1,488, mean age = 42.7 (SD = 12.6)) receiving outpatient care from Michigan Medicine, the University of Michigan health system. Enrolment quotas were established to ensure a diverse sample—one-third of participants identified as African American/Black, one-third Hispanic/Latino, one-third White, and one-third low-income. Participants reported engaging in more behaviours that are supportive of a sustainable diet one year into the COVID-19 pandemic compared to before. This is particularly true regarding ecologically and economically sustaining behaviours such as taking fewer trips to the grocery store, increased use of home grocery delivery, increased cooking at home, and greater consumption of healthy foods. Not all behaviour changes promoted sustainable food systems; namely, the use of farmer’s markets and Community Supported Agriculture (CSAs) declined. White and high-income participants were more likely than African American/Black, Hispanic/Latino, and low-income individuals to engage in ecologically and economically sustainable dietary behaviours during the pandemic. Meanwhile, African American/Black participants reported large increases in physical health sustainable dietary behaviours. To support the continuation of greater engagement with sustainable diets, policies that increase access to public transportation, limit the frequency with which consumers have groceries delivered, increase work-from-home options, and improve access for low-income populations should be prioritised.

Reducing meat consumption is essential to curb further climate change and limit the catastrophic environmental degradation resulting from the current global food system. However, consumers in industrialised countries are hesitant to reduce their meat intake, often because they find plant-based foods less appealing. Despite the climate emergency, eating meat is still perceived as the norm, and recommended in most national dietary guidelines. To support the transition to more sustainable diets by providing insights for increasing the appeal of plant-based foods to mainstream consumers, this review presents recent research findings on how people think and communicate about meat-based and plant-based foods. The key findings we review include: (1) while vegans think about plant-based foods in terms of enjoyable eating experiences, omnivores think about plant-based foods in terms of health, vegan identity and other abstract information that does not motivate consumption in the moment. (2) Packages of ready-meals and social media posts on Instagram present plant-based foods with fewer references to enjoyable eating experiences than meat-based foods. (3) Presenting plant-based foods with language that references enjoyable eating experiences increases their appeal, especially for habitual meat eaters. This language includes words about sensory features of the food (e.g., crunchy, creamy), eating context (e.g. pub; with family) and immediate positive consequences of eating (e.g. comforting, delicious). In contrast, the term ‘vegan’ is strongly associated with negative stereotypes. Hence, rather than referring to being vegan, meat-free or healthy, the language used for plant-based foods should refer to sensory appeal, attractive eating situations and enjoyment.

Globally, diet quality is poor, with populations failing to achieve national dietary guidelines. Such failure has been consistently linked with malnutrition and poorer health outcomes. In addition to the impact of diet on health outcomes, it is now accepted that what we eat, and the resulting food system, has significant environmental or planetary health impacts. Changes are required to our food systems to reduce these impacts and mitigate the impact of climate change on our food supply. Given the complexity of the interactions between climate change, food and health, and the different actors and drivers that influence these, a systems-thinking approach to capture such complexity is essential. Such an approach will help address the challenges set by the UN 2030 Agenda for sustainable development in the form of the sustainable development goals (SDG). Progress against SDG has been challenging, with an ultimate target of 2030. While the scientific uncertainties regarding diet and public and planetary health need to be addressed, equal attention needs to be paid to the structures and systems, as there is a need for multi-level, coherent and sustained structural interventions and policies across the full food system/supply chain to effect behaviour change. Such systems-level change must always keep nutritional status, including impact on micronutrient status, in mind. However, benefits to both population and environmental health could be expected from achieving dietary behaviour change towards more sustainable diets.

The focus of nutritionists is on improvement of the health impact of current diets. Therefore, it is important to ask the question whether healthy diets are more sustainable. This review provides an overview on the research on synergies between health and sustainability. Synergies are found from shifts from animal-based to plant-based diets, from ultra-processed foods to fresh and whole foods and from reduction of food waste. The importance of looking at sustainability of the present diets has led to steps made in Europe to incorporate sustainability into food-based dietary guidelines. Examples from UK, Nordics, Belgium and the Netherlands are given. World Wildlife Fund has summarised the insides in a future-proof diet: the planet-based diet within planetary boundaries.

The gut microbiome is a key element for health preservation and disease prevention. Nevertheless, defining a healthy gut microbiome is complex since it is modulated by several factors, such as host genetics, sex, age, geographical zone, drug use, and, especially, diet. Although a healthy diet has proven to increase microbial alpha and beta diversity and to promote the proliferation of health-related bacteria, considering the current environmental and nutritional crisis, such as climate change, water shortage, loss of diversity, and the obesity pandemic, it should be highlighted that a healthy diet is not always sustainable. Sustainable diets are dietary patterns that promote all dimensions of people’s health and well-being while exerting low pressure on the environment, and being accessible, affordable, safe, equitable, and culturally acceptable. Examples of diets that tend to be sustainable are the Planetary Health Diet of the EAT-Lancet Commission or territorial diets such as the Mediterranean and the Traditional Mexican diet (milpa diet), adapted to specific contexts. These diets are principally plant-based but include small or moderate amounts of animal-based foods. Characterising the effects of sustainable diets on gut microbiota is urgent to ensure that the benefits for human health are aligned with environmental preservation and respect the sociocultural aspects of individuals.

The transition towards more plant-based diets may pose risks for bone health such as low vitamin D and Ca intakes. Findings for the contribution of animal and plant proteins and their amino acids (AA) to bone health are contradictory. This 6-week clinical trial aimed to investigate whether partial replacement of red and processed meat (RPM) with non-soya legumes affects AA intakes and bone turnover and mineral metabolism in 102 healthy 20–65-year-old men. Participants were randomly assigned to diet groups controlled for RPM and legume intake (designed total protein intake (TPI) 18 E%): the meat group consumed 760 g RPM per week (25 % TPI) and the legume group consumed non-soya legume-based products (20 % TPI) and 200 g RPM per week, the upper limit of the Planetary Health Diet (5 % TPI). No differences in bone (bone-specific alkaline phosphatase; tartrate-resistant acid phosphatase 5b) or mineral metabolism (25-hydroxyvitamin D; parathyroid hormone; fibroblast growth factor 23; phosphate and Ca) markers or Ca and vitamin D intakes were observed between the groups (P > 0·05). Methionine and histidine intakes were higher in the meat group (P ≤ 0·042), whereas the legume group had higher intakes of arginine, asparagine and phenylalanine (P ≤ 0·013). Mean essential AA intakes in both groups met the requirements. Increasing the proportion of non-soya legumes by reducing the amount of RPM in the diet for 6 weeks did not compromise bone turnover and provided on average adequate amounts of AA in healthy men, indicating that this ecologically sustainable dietary change is safe and relatively easy to implement.

Mexico is going through an environmental and nutritional crisis related to unsustainable dietary behaviours. Sustainable diets could solve both problems together. This study protocol aims to develop a three-stage, 15-week mHealth randomised controlled trial of a sustainable-psycho-nutritional intervention programme to promote Mexican population adherence to a sustainable diet and to evaluate its effects on health and environmental outcomes. In stage 1, the programme will be designed using the sustainable diets, behaviour change wheel and capability, opportunity, motivation, and behaviour (COM-B) models. A sustainable food guide, recipes, meal plans and a mobile application will be developed. In stage 2, the intervention will be implemented for 7 weeks, and a 7-week follow-up period in a young Mexican adults (18–35 years) sample, randomly divided (1:1 ratio) into a control group (n 50) and an experimental group (n 50), will be divided into two arms at week 8. Outcomes will include health, nutrition, environment, behaviour and nutritional-sustainable knowledge. Additionally, socio-economics and culture will be considered. Thirteen behavioural objectives will be included using successive approaches in online workshops twice a week. The population will be monitored using the mobile application consisting of behavioural change techniques. In stage 3, the effects of the intervention will be assessed using mixed-effects models on dietary intake and quality, nutritional status, physical activity, metabolic biomarkers (serum glucose and lipid profile), gut microbiota composition and dietary water and carbon footprints of the evaluated population. Improvements in health outcomes and a decrease in dietary water and carbon footprints are expected.

Dietary behaviours and the food systems in which they occur have a significant impact on climate change. The 2022 Intergovernmental Panel on Climate Change (IPCC) reports and other major climate reports have identified population-level dietary shifts towards balanced, sustainable healthy diets as an important mitigation (i.e. prevention) solution for climate change. Thus, public health nutrition researchers and practitioners have a crucial role to play in combatting the climate crisis. They have the content expertise, interdisciplinary training and technical skills needed to facilitate wide-scale dietary behaviour changes at multiple levels of influence and ultimately improve both human and planetary health. This commentary article: (i) summarises how dietary behaviours and food systems contribute to climate change, with a particular focus on high-income countries; (ii) reviews food-system-related climate change mitigation solutions most relevant to public health nutrition researchers and practitioners; and (iii) identifies key gaps in the literature and future research directions for the field.