Planetary Health Diet Index in relation to mortality in a prospective cohort study of U.S. Black females.

Background: To improve both human health and the health of our planet, the EAT-Lancet Commission proposed the planetary health diet (PHD).

Objective: We aimed to evaluate associations of PHD with all-cause, cardiovascular disease (CVD), and cancer-specific mortality among U.S. Black females.

Methods: The Black Women's Health Study is a prospective study of self-identified U.S. Black females. In 2001, 33,824 participants free of cancer and CVD completed a validated food frequency questionnaire. PHD Index (PHDI) was calculated based on reported consumption of 15 food groups, such as whole grains, non-starchy vegetables, legumes, soy foods, added fat and trans fat, and red/processed meats. Deaths were identified through linkage to the National Death Index. Cox proportional hazards regression, stratified by age and adjusted for smoking status, body mass index, and other CVD risk factors, was used to calculate hazards ratios (HRs) for quintiles of PHDI in relation to all-cause, CVD-, and cancer-specific mortality.

Results: During 18 years of follow-up, we identified 3537 deaths, including 779 from CVD and 1625 from cancer. Females in the quintile representing highest adherence to PHD were estimated to have a 18% reduction in risk of all-cause mortality (HR=0.82, 95% CI: 0.71, 0.94) and 26% reduction in CVD-specific mortality (HR=0.74, 95% CI: 0.55, 0.98), compared to those in the lowest quintile, with similar reductions observed for quintiles 2, 3, and 4. Among individuals under age 55, there was a significant trend of lower CVD mortality risk with higher level of adherence to PHD (p =0.004) and the HR for the highest versus lowest quintile was 0.43 (95% CI: 0.21, 0.87). PHDI was not associated with cancer-specific mortality.

Conclusions: Adherence to a diet that has been shown to benefit the planet was associated with a lower risk of mortality among Black females, primarily driven by reduction in CVD-specific mortality risk.