Planetary Health Diet Index in relation to mortality in a prospective cohort study of United States Black females

Abstract

Background

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

Objectives

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

Methods

The Black Women’s Health Study is a prospective study of self-identified United States 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, nonstarchy 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 hazard 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 the highest adherence to PHD were estimated to have an 18% reduction in risk of all-cause mortality [HR = 0.82, 95% confidence interval (CI): 0.71, 0.94] and 26% reduction in CVD-specific mortality (HR = 0.74, 95% CI: 0.55, 0.98), compared with 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 a higher level of adherence to PHD (P_trend = 0.004), and the HR for the highest compared with the 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 a reduction in CVD-specific mortality risk.