Balancing human and planetary health through multicriteria optimization: Insights from the NutriNet-Santé cohort

Food systems contribute to environmental degradation and diet-related diseases. While numerous dietary recommendations exist, systematic quantification of trade-offs between health and environmental objectives remains limited, particularly in France, where no such optimization study has been conducted. We applied multi-criteria optimization to map the Pareto front between health risk (based on Global Burden of Disease targets) and environmental pressures (greenhouse gas emissions, water use, land occupation, pesticide use, ecological infrastructure, and energy demand). We identified optimal diets under varying acceptability constraints that limit deviations from current dietary patterns. Baseline data were from 29,413 NutriNet-Santé cohort participants (France, 2014). The Pareto front reveals both substantial co-benefits and conflicts between health and environmental objectives. One optimal solution with relaxed acceptability constraints features 700g fruits/vegetables daily, 60g pulses, 290g whole grains, 350mL milk and 70g other dairy daily, up to 35g poultry weekly and 250g fish weekly. Compared to baseline, this diet improves health score by 145% while reducing overall environmental pressures by 18%, with decreases of 73% (GHG emissions), 59% (land occupation), 55% (energy demand), 79% (pesticide use), and 6% (water use). The proportion of organic food increases by 161% and costs remain stable (±3%). However, ecological infrastructure decreased by 47%, revealing trade-offs between biodiversity preservation and other environmental goals. This first comprehensive analysis for France systematically quantifies health-environment trade-offs, revealing where objectives align and conflict, thereby providing evidence to inform public policies balancing human and planetary health. Despite substantial dietary changes, these diets remain feasible and affordable. The NutriNet-Sante cohort is registered at clinicaltrials.gov (NCT03335644). • Whether the emphasis is on optimising human health or preserving the environment, indicators from all to sustainability domains showed improvement compared with the current situation • Optimal diets are rich in organic foods and plant-based foods, and their cost is close to the cost of the current situation • Depending on whether the model opts for a conservative or disruptive approach regarding acceptability, health risks, and greenhouse gas emissions were reduced by 87%/66% to 94%/73% respectively • The healthy and sustainable diets varying from strict to flexible acceptability criteria were all high in plant-based and organic foods