Protein transition and circular food system transition are two proposed strategies for supporting food system sustainability. Here we model animal-sourced protein to plant-sourced protein ratios within a European circular food system, finding that maintaining the current animal–plant protein share while redesigning the system with circular principles resulted in the largest relative reduction of 44% in land use and 70% in greenhouse gas (GHG) emissions compared with the current food system. Shifting from a 60:40 to a 40:60 ratio of animal-sourced proteins to plant-sourced proteins yielded a 60% reduction in land use and an 81% GHG emission reduction, while supporting nutritionally adequate diets. Differences between current and recommended total protein intake did not substantially impact minimal land use and GHG emissions. Micronutrient inadequacies occurred with less than 18 g animal protein per capita per day. Redesigning the food system varied depending on whether land use or GHG emissions were reduced—highlighting the need for a food system approach when designing policies to enhance human and planetary health.

The triple burden of obesity, undernutrition and climate change calls for systemic action to find solutions that co-benefit human and planetary health. A Nutritional Life Cycle Assessment (nLCA) can be used as a tool to assess the health- and environmental impact of foods and guide a transition to healthy and sustainable diets. Thus far, nLCAs have used the nutrient content of foods to represent their health impact, whereas the disease risk linked to under- or overconsuming certain nutrients, foods or food groups has been largely underutilized. This study explored, for the Dutch diet, the correlation between an indicator for essential nutrient density and for the disease burden of individual food items, i.e., a Nutrient Rich Food index with 24 essential nutrients (NRF24) and the HEalth Nutritional Index (HENI), respectively. NRF24 and HENI scores were calculated for food items contained in the Dutch Food Composition database. A very weak correlation between NRF24 and HENI values confirmed that nutrient density and disease burden should be considered as complementary and thus, that a high nutrient density does not directly imply a low disease burden, and vice versa. Moreover, the direction and strength of the correlation was food group-dependent, with negative correlations between NRF24 and HENI mainly observed for animal-based products, with the exception of dairy. In addition, the correlations between the nutrition-based indicators and indicators for greenhouse gas emissions, land use and water use were mostly weak, which stresses the need to include health impact in traditional LCAs because foods with a high nutrient density and low disease burden can imply trade-offs due to high environmental impacts. We therefore conclude that multiple indicators for health and environmental impact should be considered side-by-side in nLCA to avoid the risk of missing important information and trade-offs when assessing the performance of individual food items for healthy and sustainable diets.

The global food system is facing the challenge of producing sufficient nutrients to accommodate future demands within planetary boundaries, while reducing malnutrition. Although nutrient-rich seafood can play a prominent role in resolving this challenge, seafood from capture fisheries is currently partly wasted. Here we quantified the nutrient contribution from capture fisheries through a hypothetical scenario that assumed all captured seafood and byproducts from seafood processing would be used for human consumption. Our simulations show that available seafood per capita can be doubled without increasing the pressure on global fisheries when all reported, illegal, and discarded capture is used as food, complemented with processing byproducts. In such a scenario, seafood contributes greatly to daily nutrient requirements – e.g., omega-3 can be fully met. Although uncertainty should be considered, these results indicate that putting the whole fish on the table can increase nutrient availability from capture fisheries substantially and sustainably.

Background and objectives: There is a compelling need for a more sustainable food system because of climate change and contemporary Western diets, which pose a threat to human and planetary health. The food system is a social–ecological system, consisting of both biophysical and social sub-systems which are interlinked. This implies that changes in one sub-system can lead to synergies and trade-offs elsewhere. To identify such synergies and tradeoffs, researchers are integrating work from a range of disciplines in optimization models. This has resulted in models that are unique but have a similar overarching aim: ‘to create a sustainable food system by understanding the implications of food system choices’. However, the results of these models may differ. Therefore, the aim of this paper was to understand the differences and complementarity of two optimization models to grasp the complexity of the food system. Methods: we compared the Circular Food System (CiFoS) model with the Sustainable, Healthy, Acceptable, Realistic, and Preferable diets (SHARP) model. CiFoS is a biophysical optimization model that aims to produce a healthy diet for a growing population within planetary boundaries. SHARP is a benchmarking model that optimizes current diets for health and sustainability for consumers. Both models propose a healthy and sustainable diet. While CiFoS is detailed on how environmental impacts are calculated, SHARP has a finer grid on the consumption aspects. Results: based on previously modelled scenarios that showed different results in diet composition, we identified that these differences could be explained by fundamental characteristics of the model (e.g., environmental impact calculations or the consideration of distance to the current diet), data input and scenario settings. Besides, the models work complementary regarding the time scale (i.e., solutions for the upcoming years versus upcoming decades), geographic scale and an individual versus population approach. Conclusion: Optimization models may be used for the same goal, e.g., finding an optimal diet, but the nuance chosen will lead to different outcomes. The outcomes of such models are complementary and can therefore be used in conjunction to inform policy or other food system stakeholders.

A protein transition is promoted as a pathway toward a sustainable food system, but its application and progress are potentially hindered by diverse, often conflicting narratives among various stakeholders. These narratives are constituted and underpinned by statements and nurture a growing polarisation by isolation of their underlying scientific evidence. The multidimensional and interdisciplinary nature of a protein transition does not go well with an isolated approach in academia. The latter leads to fragmented and incomplete scientific evidence that fails to fully grasp the complexity of the issue, while being used to form partial statements that feed societal and political debates. Through a Restatement approach, this paper aims to (i) synthesise scientific evidence from multiple academic disciplines related to a protein transition and (ii) critically reflect on the implications of the current fragmented scientific evidence landscape of a protein transition in academia and beyond. The Restatement is structured into three sections: Background, Context, and Impacts, with subsections that each cover 4–17 statements, with a total of 68 statements. We connected each statement to its supporting scientific evidence which revealed the complexity of how evidence is related and interpreted, in addition to the inconsistent use of terminology and resulting ambiguities. The main takeaway from the Restatement is that a protein transition cannot be reduced to a single message of a dietary shift but that it should be approached more holistically, while using the available evidence within the appropriate context and critical consideration of the methodologies used to obtain that evidence. This Restatement can be used by researchers and decision-makers working toward more sustainable food systems in the European Union and beyond, to understand the contexts and methods that are not within their own field of expertise. In addition, we stress that overcoming polarisation in a protein transition largely relies on critical reflections of the assumptions, interests and power dynamics shaping the protein transition debate.