Exploring eight-year trajectories of diet-related environmental pressures in the NutriNet-Santé cohort

Few studies have explored individual diet-related environmental pressure changes, beyond greenhouse gas emissions (GHGe) and land occupation (LO). This study evaluates the trajectories in several environmental impacts of diets among 8,905 French adults from the NutriNet-Santé cohort, who completed food frequency questionnaires (distinguishing organic vs. conventional foods) in 2014, 2018, and 2022. Six environmental indicators-GHGe, LO, energy demand, ecological infrastructure use, water use, and pesticide use-were estimated at the farm perimeter using a multi-source approach. Latent class models identified trajectories for a composite environmental pressure index (EPI) and each indicator, and mixed models adjusted for energy intake and sex modeled the trajectories. On average, most environmental pressures decreased over time (e.g., GHGe by -12%, water use by -1%), indicating a general improvement. However, ecological infrastructure also declined (-9%), which represents a negative outcome as it is linked to biodiversity. Two to four trajectory profiles were identified per indicator, with most individuals showing stable or modestly decreasing trends. Four EPI trajectories emerged: increasing EPI profiles were associated with higher meat consumption, whereas decreasing EPI reflected shifts toward more plant-based diets. Despite potential awareness of the importance of sustainable diets, this study reveals that most individuals show moderate improvements in their diet-related environmental pressures, with only a very small fraction showing important decreases.