Planetary health diet and cardiovascular disease: results from three large prospective cohort studies in the USA

Background

In 2019, the EAT–Lancet Commission on healthy diets from sustainable food systems proposed a Planetary Health Diet that seeks to optimise both chronic disease prevention as well as global environmental health. In this study, we aimed to examine the association between a dietary index based on the Planetary Health Diet and risk of cardiovascular disease.

Methods

We included women from the Nurses’ Health Study (NHS I; 1986–2016), women from the Nurses’ Health Study II (NHS II; 1991–2017), and men from the Health Professionals Follow-up Study (HPFS; 1986–2016) who were free of cardiovascular disease, cancer, and diabetes at baseline. Dietary data were collected every 4 years using a validated, semi-quantitative food frequency questionnaire. The Planetary Health Diet Index (PHDI) was based on 15 food groups: whole grains, vegetables, fruit, fish and shellfish, nuts and seeds, non-soy legumes, soy foods, and unsaturated oils were scored positively; starchy vegetables, dairy, red or processed meat, poultry, eggs, saturated fats and trans fat, and added sugar received negative scores. Scores for each food group were summed to get a total score of 0–140. Higher scores indicated greater adherence to the PHDI. We used Cox proportional hazards regression with time-varying covariates to evaluate the association between PHDI score, cumulatively averaged, and incident cardiovascular disease (defined as fatal and non-fatal myocardial infarction and stroke), adjusting for demographic, health, and lifestyle confounders in all participants with available data. Cohort-specific estimates were combined using inverse variance-weighted fixed effects meta-analyses.

Findings

Of the 62 919 women included from the NHS I, 88 535 women included from the NHS II, and 42 164 men included from the HPFS, a total of 9831 cases of cardiovascular disease were confirmed over 4 541 980 person-years of follow-up. Mean PHDI scores ranged from 60·7 (SD 5·1) to 90·6 (5·3) in the lowest versus highest quintile in NHS I, 55·6 (4·9) to 86·3 (6·3) in NHS II, and 59·6 (5·9) to 94 (5·9) in HPFS. In the multivariable-adjusted meta-analysis, participants in the highest quintile of PHDI score had a lower risk of incident cardiovascular disease than did those in the lowest quintile (hazard ratio [HR] 0·83 [95% CI 0·78–0·89]; p-trend <0·0001). When we examined cardiovascular disease subtypes, the highest quintile of PHDI was also associated with a lower risk of coronary heart disease (HR 0·81 [95% CI 0·74–0·88]; p-trend <0·0001) and total stroke (HR 0·86 [0·78–0·95]; p-trend=0·0004) compared with the lowest quintile.

Interpretation

We found that adherence to the Planetary Health Diet, designed to be a more environmentally sustainable dietary pattern, was associated with a lower risk of cardiovascular disease in three large cohorts of men and women in the USA. These observations support the Planetary Health Diet as a promising strategy to promote both human and planetary health.