Sustainable diets within a sustainable food systems perspective

For over 12,000 years, humanity has thrived under stable climatic conditions that sustain Earth’s balance. However, the Planetary Boundaries (PB) framework posits that exceeding certain environmental limits could disrupt this stability, potentially jeopardizing human survival. Agriculture and food systems significantly contribute to PB transgressions, with four already breached—climate change, biodiversity loss, land system change, and nutrient cycles. Sustainable Development Goals (SDGs) are at risk, as nearly half of current food production relies on practices that exceed PB limits, underscoring the urgent necessity for transformative action in food systems and climate policies. Despite global commitments, such as the COP28 roadmap, current efforts are insufficient to achieve the 1.5 °C climate target or attain the SDGs by 2030. Suboptimal diets contribute to 22% of global mortality, and food security remains a significant concern as 30% of the population experiences food insecurity. Sustainable diets are contingent upon resilient food systems, which are influenced by environmental, economic, sociocultural, and political factors. While frameworks such as the Planetary Health Diet and food-based dietary guidelines offer potential solutions, challenges persist in aligning diets with cultural and economic realities, as well as creating supportive food environments. To address these challenges, this doctoral thesis will focus on developing evidence-based recommendations for policymakers. The research will assess food systems comprehensively from a dietary perspective, considering health, environmental, economic, and socio-cultural dimensions, to inform structural policy changes that promote sustainable diets for all. Achieving this balance is critical to mitigate environmental impacts, enhancing public health, and ensuring global food security. This Doctoral Thesis comprises five studies conducted with the objective of estimating and promoting sustainable diets. The initial study proposed a mathematical optimization model for transforming current diets into four-dimensional sustainable diets and determining their feasibility. Furthermore, this study compared various data sources to estimate their differences at the result level, and different optimization models were implemented for national and sub-national population groups. Subsequently, two global reviews were conducted to ascertain the promotion of sustainable diets at a national public policy level. The first review examined food-based dietary guidelines’ iconographies to assess the extent to which dietary guidelines depict sustainability dimensions and messages within their graphics. The second review analyzed the evidence of food eco-labeling to understand its impact and propose recommendations for decision-makers when implementing eco-labels. Finally, two additional studies were conducted to evaluate food environments and nudge interventions in different work settings. The first study involved the development of an ICT application to educate, communicate, and nudge workers to choose healthier options in the work canteen. The second study investigated the differences in food-at-work conditions among various types of workers, focusing on office and remote work food environments, eating habits, and overall dietary conditions. Our findings demonstrated that a multi-objective mathematical model can incorporate four dimensions of sustainability to evaluate and propose these types of diets. Four-dimensional sustainable diets are feasible under all constraints considered, for the national and sub-national population groups in Chile. This methodology could be applied to any population group. However, attention should be directed to data sources for estimating these diets. Subsequently, we determined that Food-Based Dietary Guidelines (FBDGs) and other national dietary guidelines iconographies fail to depict four-dimensional sustainable diets. Only 8 guidelines at the global level incorporated the four dimensions, and although sustainability is increasingly being considered over time, the economic and socio-cultural dimensions are typically underrepresented. When examining food environments in greater depth, we found that eco-labels are effective tools to communicate sustainability aspects of foods at the point of purchase; however, the policy design and its implementation must be carefully developed. Furthermore, when assessing food environments in workplaces, we found that ICT applications and nudges are effective in motivating and guiding consumers toward more sustainable and healthier choices; however, improved outcomes could potentially be achieved if the canteen food offers are also modified. Lastly, the study conducted to understand workers’ food conditions and the comparison made between working from home and at work revealed that food benefits vary significantly among different types of workers deepening inequity, and that working from home appears to be a protective factor for healthier diets, as workers reported cooking healthier meals at home and noted that fewer healthy options were available at the office, where they were more susceptible to unhealthy food choices. This doctoral thesis elucidates the viability of four-dimensional sustainable diets, which balance health, planetary boundaries, economic accessibility, and alignment with current dietary patterns. Through the utilization of an optimization model, it facilitates the adaptation of sustainable dietary options for diverse populations based on regional requirements. However, the study underscores the influence of data sources and methodological choices, such as the use of national versus international dietary data form FAO, thresholds for affordability, and food waste considerations, which can significantly impact the results. Additionally, FBDGs have demonstrated a gradual trend towards integrating sustainability, although aspects such as affordability, personal preferences, and gender roles still necessitate further attention. Furthermore, the thesis indicates the potential of food eco-labels and ICTs as efficacious tools to guide consumer choices, particularly in workplace settings where dietary quality tends to decline. However, the effectiveness of these tools is largely contingent upon the visibility and clarity of their messages. A workplace-focused intervention utilizing ICTs could promote healthier choices, although the benefits would be amplified with a more comprehensive food environment redesign. In conclusion, the thesis posits that sustainable diets, implemented across various levels from national policies to workplace canteens, support both human and planetary health. Economic and cultural considerations must remain central to these interventions for their successful implementation in diverse food systems.