A three-dimensional dietary index (nutritional quality, environment and price) and reduced mortality: The "Seguimiento Universidad de Navarra" cohort

Several healthy diet indices have been associated with mortality risk. However, the ideal diet should not only be healthy but also environmentally friendly and affordable. The study aimed to determine if a new Sustainable Diet Index (SDI), which takes into account the nutritional quality, environmental impacts and market price of diets, was associated with all-cause and cause-specific mortality. Using data from the "Seguimiento Universidad de Navarra" Project, a prospective cohort study of Spanish university graduates, the study included 15,492 participants who were recruited between December 1999 and March 2014 and followed-up for a median of 10 years. Cox regression was used to determine the relationship of SDI and its components with all-cause and cause-specific mortality risk. Hazard ratios with adjustment for several confounders were calculated. The weights for the foods contributing to the SDI were assessed with multiple regression analyses and variability with nested regression analyses. The highest quartile of the SDI scores was associated with a 59% relative reduction in all-cause mortality (HR 0.41, 95% CI 0.23-0.75; P-trend < 0.001) and 79% reduction in cardiovascular mortality (HR 0.21, 95% CI 0.05-0.85; P-trend < 0.001). SDI was positively correlated with beans and potato consumption but negatively correlated with red meat intake. Red and processed meats, fatty dairy products and fish consumption accounted for most of the variability in the SDI. Altogether, dietary patterns accounting not only for nutritional quality of the food but also the impact on the environment and affordability could still provide health benefits.