Planetary Health Diet Index Trends and Associations with Dietary Greenhouse Gas Emissions, Disease Biomarkers, Obesity, and Mortality in the United States (2005-2018).

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Diet plays a vital role in human health and environmental effects. Monitoring diet quality and its relationship to both health and environment are essential for policy making. This study aimed to analyze trends in the Planetary Health Diet Index (PHDI) and its associations with daily greenhouse gas emissions from food (GHG), disease-related biomarkers, anthropometric measurements, obesity, and all-cause mortality in the US population. We analyzed 27,181 adults in the National Health and Nutrition Examination Survey (NHANES) from 2005 to 2018 except for the mortality analysis. 23,599 adults were analyzed as the 2017-2018 NHANES dietary data were removed due to the potential for reverse causation. We calculated PHDI scores by using two 24-hour dietary recalls and GHG by linking the consumption of individual foods to dataFRIENDS, a food-environmental impact database. To assess associations with the PHDI, we used generalized linear regression models for GHG, disease-related biomarkers, and obesity, and used the Cox proportional hazards model for all-cause mortality. The energy-adjusted mean of the PHDI (140 possible points) increased from 68.6 in 2005-2006 to 71.7 in 2017-2018 (p for trend < 0.001). When compared to the lowest quintile (Q1), the highest PHDI quintile (Q5) was associated with 25% lower GHG emissions, a better cardiometabolic profile, lower prevalence ratios of obesity (0.59, 95% CI: 0.50-0.69) and abdominal obesity (0.74, 95% CI: 0.66-0.82) and a lower risk of all-cause death (HR: 0.65, 95% CI: 0.54-0.78). These results underscore the potential health and greenhouse gas emission benefits aligned with the planetary health diet.