Plant‐Based Diets and the Risk of Coronary Heart Disease in US Adults

Plant-based diets are recommended for coronary heart disease (CHD) prevention. However, all plant foods are not necessarily beneficial. In addition, prior studies have defined plant-based diets dichotomously as 'vegetarian' diets; it is not clear how gradual reductions in animal food intake affect cardiovascular health. Thus we aimed to evaluate how graded plant-based diet indices prospectively relate with CHD. We included 73,710 women in the Nurses' Health Study (NHS), 92,329 women in NHS2, and 43,247 men in the Health Professionals Follow-up Study (HPFS), free of chronic diseases at baseline (1984 for NHS, 1991 for NHS2, and 1986 for HPFS). We created an overall plant-based diet index (PDI) from dietary data collected every 4 years using food frequency questionnaires, by assigning positive scores to plant foods and reverse scores to animal foods. We also created a healthful PDI (hPDI) where healthy plant foods (whole grains, fruits/vegetables, nuts/legumes, oils, tea/coffee) received positive scores, while less healthy plant foods (juices/sweetened beverages, refined grains, potato/fries, sweets) and animal foods received reverse scores. We created an unhealthful PDI (uPDI) by assigning positive scores to less healthy plant foods, and reverse scores to healthy plant foods and animal foods. The indices were cumulatively averaged over the follow-up till development of major outcomes (type 2 diabetes, stroke, and cancer). Over 4,774,135 person-years of follow-up, we documented 7880 cases of CHD. After pooling across the cohorts and adjusting for confounders, the overall plant-based diet was inversely associated with CHD (HR comparing extreme deciles: 0.90, 95% CI: 0.81–1.00; p trend=0.002). This inverse association was stronger for hPDI (HR comparing extreme deciles: 0.74, 95% CI: 0.66–0.82; p trend<0.001). On the other hand, uPDI was positively associated with CHD (HR comparing extreme deciles: 1.37, 95% CI: 1.24–1.53; p trend<0.001). The results were largely unchanged when we adjusted for additional variables, continuously updated the indices throughout follow-up, used baseline values of the indices, used the most recent index scores before CHD diagnosis, and when we stopped updating the indices when intermediate conditions such as hypertension developed (Fig 1). The inverse association of hPDI with CHD was consistently observed across strata defined by age, body mass index, CHD family history, and smoking status. Plant-based diets, especially when rich in healthier plant foods, are associated with substantially lower risk of developing CHD. These findings support current recommendations to increase intake of healthy plant foods, while reducing intake of less healthy plant foods and certain animal foods. Future research should explore the biological mechanisms involved in the potentially cardio-protective effects of healthful plant-based diets. Support or Funding Information This work was supported by research grants UM1 CA186107, UM1 CA176726, UM1 CA167552, R01 HL034594, and R01 HL35464 from the National Institutes of Health. a Adjusted for key confounders. Diet cumulatively averaged till development of stroke/cancer/diabetesb Additionally adjusted for ethnicity, marital status, recent physical exam, diet beverage intake, socio-economic statusc Adjusted for potential intermediates (updated hypertension, hypercholesterolemia, diabetes)d Diet cumulatively averaged through follow-upHT, Hypertension; HC, Hypercholesterolemia