Adherence to a Planetary Health Diet, Environmental Impacts, and Mortality in Chinese Adults

IMPORTANCE: Although the EAT-Lancet Commission has recently proposed a planetary health diet (PHD) to promote human and environmental health, little is known about how PHD affects environment and mortality risk among an Asian population. OBJECTIVE: To investigate whether a PHD score is associated with environmental impacts and mortality outcomes in a Chinese cohort living in Singapore. DESIGN, SETTING, AND PARTICIPANTS: This cohort study used data from the Singapore Chinese Health Study. Eligible participants were without known cardiovascular disease and cancer at baseline; they were recruited between 1993 and 1998 and followed up using record linkage data until 2020. Data were analyzed from September 2022 to April 2023. EXPOSURES: PHD score was calculated based on the reference consumption of 14 dietary components in PHD and individual energy intake assessed using a validated food frequency questionnaire in this cohort. MAIN OUTCOMES AND MEASURES: Diet-related environmental impacts were estimated using a food frequency questionnaire. Mortality outcomes (all-cause, cardiovascular disease, cancer, and respiratory disease) were identified via linkage with a nationwide registry. RESULTS: A total of 57 078 participants were included in this study (mean [SD] age, 56.1 (7.9) years; 31 958 women [56.0%]). During a median (IQR) follow-up of 23.4 (18.7-26.2) years, 22 599 deaths occurred. Comparing the highest and lowest quintiles, higher PHD scores were associated with lower greenhouse gas emissions (β = −0.13 kg CO(2) equivalent; 95% CI, −0.14 to −0.12 kg CO(2) equivalent), but with higher total water footprint (β = 0.12 m(3); 95% CI, 0.11-0.13 m(3)) and land use (β = 0.29 m(2); 95% CI, 0.28-0.31 m(2)). In the adjusted multivariable model, compared with the lowest quintile, participants in the highest quintile of PHD score had lower risk of all-cause mortality (hazard ratio [HR], 0.85; 95% CI, 0.81-0.89), cardiovascular disease mortality (HR, 0.79; 95% CI, 0.73-0.85), cancer mortality (HR, 0.93; 95% CI, 0.86-1.00), and respiratory disease mortality (HR, 0.81; 95% CI, 0.74-0.89). CONCLUSIONS AND RELEVANCE: In this study of Singapore Chinese adults, higher adherence to PHD was associated with reduced risk of chronic disease mortality. However, environmental impacts were uncertain, as higher adherence was associated with lower greenhouse gas emissions but higher total water footprint and land use.