Comparing nutritional, economic, and environmental performances of diets according to their levels of greenhouse gas emissions

In response to climate change, reduction of GHGEs (greenhouse gas emissions) from food systems is required. Shifts of agricultural practices and dietary patterns could reduce GHGEs. We aimed to characterize observed diets with different levels of GHGEs and compare their nutritional, economic, and environmental performances. Food consumptions of 34,193 French adults participating in the NutriNet-Sante Cohort were assessed using a food frequency questionnaire. Nutritional, environmental, and economic indicators were computed for each individual diet. Adjusted means of food group intakes, contribution of food groups to dietary GHGEs, nutritional, environmental, and economic indicators were compared between weighted quintiles of GHGEs. Diets with high GHGEs (ranging from 2318 to 4099 kgCO2eq/year) contained more animal-based food and provided more calories. Few differences were found for unhealthy food (alcohol or sweet/fatty food) consumption across the categories of dietary GHGEs. Diets with low GHGEs were characterized by a high nutritional quality. Primary energy consumption and land occupation increased with GHGEs (from Q1: 3978 MJ/year (95%CI = 3958–3997) to Q5: 8980 MJ/year (95%CI = 8924–9036)) and (from Q1: 1693 m2/year (95%CI = 1683–1702) to Q5: 7188 m2/year (95%CI = 7139–7238)), respectively. Finally, participants with lower GHGE related-diets were the highest organic food consumers. After adjustment for sex, age, and energy intake, monetary diet cost increased with GHGEs (from Q1: 6.89€/year (95%CI = 6.84–6.93) to Q5: 7.68€/year (95%CI = 7.62–7.74)). Based on large observational cohort, this study provides new insights concerning the potential of current healthy and emergent diets with low monetary cost and good nutritional quality to promote climate mitigation. However, the question of a large acceptability remains.