Association of planetary health diet indices with diet composition, nutritional quality and environmental impacts in Italian adults

Background and aims: Sustainable diets are increasingly recognized as a key strategy to promote human health while reducing environmental impacts. The Planetary Health Diet (PHD) provides a global framework for sustainable and healthy eating patterns, but evidence on its adherence and implications in specific populations is still limited. The aim of this study was to test the level of adherence, the environmental impact, and the nutritional quality of several scores assessing the level of adherence to the PHD in a cohort of Italian individuals. Methods and results: Dietary habits were assessed through validated food frequency questionnaires while various scores have been applied to evaluate the level of adherence to PHD (ELD-I, EAT, PHDI-Cacau, NB-EAT, PHDI-Bui) in 1936 Italian adults, using the Mediterranean diet (MEDI-LITE) as reference. The environmental impact was quantified as carbon and water footprints (CF and WF) using the SU-EATABLE LIFE database. Higher adherence to PHD-related indices generally corresponded to healthier nutrient profiles, higher fiber intake, and better concordance with Italian dietary recommendations, although some indices predicted lower intake of certain nutrients (e.g., vitamin B12, calcium). The MEDI-LITE index consistently predicted higher adequacy across dietary and nutrient recommendations. Absolute CF and WF showed mixed trends across indices, while energy-standardized values (per 1000 kcal) indicated lower impacts for all PHD-related scores, apart from the ELD-I. Adherence to the Mediterranean diet was also associated with favorable energy-adjusted environmental outcomes. Conclusion: These findings reinforce the existing alignment between the intrinsic characteristics of the Mediterranean diet with both nutrition and sustainability objectives.