Relative validity of the Planetary Health Diet Index by comparison with usual nutrient intakes, plasma food consumption biomarkers, and adherence to the Mediterranean diet among European adolescents: the HELENA study.

PURPOSE: The EAT-Lancet Commission proposed an evidence-based global reference diet to improve human health within planetary boundaries. Recently, the Planetary Health Diet Index (PHDI) was developed based on the EAT-Lancet recommendations and validated among Brazilian adults. However, the relative validity of the PHDI in adolescents has yet to be assessed. Thus, we aimed to evaluate the relative validity of the PHDI in European adolescents. METHODS: We used cross-sectional data from 1804 adolescents (12.5-17.5 years) enrolled in the Healthy Lifestyle in Europe by Nutrition in Adolescence (HELENA) study. The PHDI (0-150 points) was calculated based on dietary intake data from two non-consecutive 24-h dietary recalls. Associations between the PHDI and usual nutrient intakes, plasma food consumption biomarkers, and adherence to the Mediterranean diet were evaluated using multivariable-adjusted mixed-effects linear regression models. RESULTS: Higher PHDI score was associated with greater intakes of nutrients predominantly from plant-source foods, such as vegetable protein, vitamin E, and folate and with lower intake of nutrients predominately from animal-source foods, such as total and saturated fat, cholesterol, and animal protein. Furthermore, a higher PHDI score was also positively associated with plasma ß-carotene, vitamin C, vitamin D, folate, and ferritin concentrations, while negatively associated with trans-fatty acids concentration. Moreover, higher PHDI was related to a greater adherence to the Mediterranean dietary pattern. CONCLUSIONS: The PHDI showed good relative validity among adolescents in the HELENA study. Hence, future research should assess adherence to the PHDI and long-term health outcomes.