Effects of a cafeteria-based sustainable diet intervention on the adherence to the EAT-Lancet planetary health diet and greenhouse gas emissions of consumers: a quasi-experimental study at a large German hospital

Summary Background Sustainable diets contribute to improving human health and reducing food-related greenhouse gas emissions (GHGE). Here, we established the effects of a facility-based sustainable diet intervention on the adherence to the EAT-Lancet Planetary Health Diet and GHGE of consumers. Methods In this quasi-experiment, vegan menus and educational material on sustainable diets were provided in the largest cafeteria of a German hospital for 3 months. Regular customers (> 1/week) in this cafeteria (intervention group) and in all other hospital cafeterias (control group) completed a questionnaire about their sociodemographic and dietary characteristics before and after the intervention period. We calculated difference-in-differences (DID), their 95% confidence intervals (CIs), and p-values for the adherence to the EAT-Lancet Planetary Health Diet Index (PHDI; 0–42 score points) and food-related GHGE. The protocol was registered at the German Clinical Trial Register (reference: DRKS00032620). Findings In this study population (N = 190; age range: 18–79 years; women: 67%; highest level of formal education: 63%), the mean baseline PHDI (25·1 ± 4·8 vs. 24·7 ± 5·8 points) and the mean baseline GHGE (3·3 ± 0·8 vs. 3·3 ± 0·7 kg CO2-eq./d) were similar between the intervention (n = 92) and the control group (n = 98). The PHDI increase was 0·6 points (95% CI: -0·4, + 1·6) higher in the intervention group than in the control group. This trend was stronger among frequent consumers of the vegan menu than among rare and never consumers. No between-group difference was seen for GHGE changes (DID: 0·0; 95% CI: -0·2, + 0·1 kg CO2-eq./d). Interpretation Pending verification in a longer-term project and a larger sample, this quasi-experiment in a big hospital in Germany suggests that offering vegan menus and information material in the cafeteria enhances the adherence to healthy and environmentally friendly diets among regular customers. These findings argue for making sustainable food choices the default option and for improving nutrition literacy. Funding Federal Ministry of Economic Affairs and Climate Action (BMWK), Else-Kröner-Fresenius Foundation (EKFS), Robert-Bosch Foundation (RBS).