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

Background: 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.

Objectives: 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.

Methods: 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.

Results: 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).

Conclusions: These results underscore the potential health and greenhouse gas emission benefits aligned with the planetary health diet.