Association between Diet-Related Greenhouse Gas Emissions and Mortality among Japanese Adults: The Japan Collaborative Cohort Study.

Background: Planetary and human health are highly intertwined; our current food system is associated with high greenhouse gas emissions (GHGE) and burden of disease.

Objective: The aim of this study was to investigate the associations of diet-related GHGE with all-cause and cause-specific mortality in Japan.

Methods: This study included 58,031 Japanese adults (35,078 women and 22,953 men) 40-79 y of age who participated in the Japan Collaborative Cohort Study during the period 1988-1990. Diet-related GHGE was calculated from dietary intake estimated by a validated food frequency questionnaire and previously developed GHGE tables of each food and beverage. Participants were classified into quintiles of diet-related GHGE per kg food/d. Hazard ratios (HRs) of all-cause and cause-specific mortality were calculated using the Cox proportional hazard and restricted cubic spline models.

Results: The average diet-related GHGE was $\mathrm{1,522}{g\text{-}\text{CO}}_2\text{-eq}/\mathrm{kg}\text{\hspace{0.17em}food}/d$. Over a period of 19.3 y (955,819 person-years) of median follow-up, 11,508 deaths were documented. After adjusting for lifestyle and medical history, in comparison with the fourth quintiles of diet-related GHGE, the first and fifth quintiles were associated with a higher risk of all-cause mortality: multivariable HR of all-cause mortality was 1.11 [95% confidence interval (CI): 1.05, 1.18] and 1.09 (95% CI: 1.03, 1.17) for the lowest and highest GHGE, respectively; those of cardiovascular disease mortality were 1.23 (95% CI: 1.10, 1.38) and 1.22 (95% CI: 1.08, 1.37), respectively. The diet-related GHGE range with the lowest HR of all-cause mortality was $\mathrm{1,400}-\mathrm{1,600}{g\text{-}\text{CO}}_2\text{eq}/\mathrm{kg}$ food/d ($p$ for nonlinearity $<0.001$). Replacing one serving of red meat with one serving of pulses was inversely associated with all-cause mortality ($\text{HR}=0.96$; 95% CI: 0.93, 0.99) and GHGE (mean change, $-347{g\text{-}\text{CO}}_2\text{-eq}/\mathrm{kg}/d$; 95% CI: $-353$, $-342$).

Discussion: Diet-related GHGE was associated with all-cause and cardiovascular disease mortality in a U-shaped fashion. This finding could be useful for creating a policy for sustainable shifts in dietary habits that will benefit the population and environmental health. https://doi.org/10.1289/EHP14935.