Plant-based diets and incident cardiovascular disease and all-cause mortality in African Americans: A cohort study

Abstract

Background Prior studies have documented lower cardiovascular disease (CVD) risk among people with a higher adherence to a plant-based dietary pattern. Non-Hispanic black Americans are an understudied group with high burden of CVD, yet studies of plant-based diets have been limited in this population. Methods and findings We conducted an analysis of prospectively collected data from a community-based cohort of African American adults (n = 3,635) in the Jackson Heart Study (JHS) aged 21–95 years, living in the Jackson, Mississippi, metropolitan area, US, who were followed from 2000 to 2018. Using self-reported dietary data, we assigned scores to participants’ adherence to 3 plant-based dietary patterns: an overall plant-based diet index (PDI), a healthy PDI (hPDI), and an unhealthy PDI (uPDI). Cox proportional hazards models were used to estimate associations between plant-based diet scores and CVD incidence and all-cause mortality. Over a median follow-up of 13 and 15 years, there were 293 incident CVD cases and 597 deaths, respectively. After adjusting for sociodemographic characteristics (age, sex, and education) and health behaviors (smoking, alcohol intake, margarine intake, physical activity, and total energy intake), no significant association was observed between plant-based diets and incident CVD for overall PDI (hazard ratio [HR] 1.06, 95% CI 0.78–1.42, p-trend = 0.72), hPDI (HR 1.07, 95% CI 0.80–1.42, p-trend = 0.67), and uPDI (HR 0.95, 95% CI 0.71–1.28, p-trend = 0.76). Corresponding HRs (95% CIs) for all-cause mortality risk with overall PDI, hPDI, and uPDI were 0.96 (0.78–1.18), 0.94 (0.76–1.16), and 1.06 (0.86–1.30), respectively. Corresponding HRs (95% CIs) for incident coronary heart disease with overall PDI, hPDI, and uPDI were 1.09 (0.74–1.61), 1.11 (0.76–1.61), and 0.79 (0.52–1.18), respectively. For incident total stroke, HRs (95% CIs) for overall PDI, hPDI, and uPDI were 1.00 (0.66–1.52), 0.91 (0.61–1.36), and 1.26 (0.84–1.89) (p-trend for all tests > 0.05). Limitations of the study include use of self-reported dietary intake, residual confounding, potential for reverse causation, and that the study did not capture those who exclusively consume plant-derived foods. Conclusions In this study of black Americans, we observed that, unlike in prior studies, greater adherence to a plant-based diet was not associated with CVD or all-cause mortality. In a cohort study, Leah J. Weston and colleagues investigate the associations between consumption of plant-based diets and incident cardiovascular disease and all-cause mortality in African Americans. Author summary Why was this study done? Plant-based diets have been linked, largely through studies of “vegetarian” diets, with health benefits, including lower risk of heart disease; however, studies of these associations among more general populations have produced mixed results. Investigating plant-based dietary patterns has allowed researchers to study how levels of adherence to plant-based dietary patterns and the healthfulness of plant-based diets correlate with cardiovascular disease (CVD) risk. This study was conducted to expand the generalizability of conclusions about plant-based diets and CVD risk in African American men and women in the US who were following a southern dietary pattern. What did the researchers do and find? We used data on 3,635 African American adults from the Jackson Heart Study with a mean follow-up of 13 years to assess the association of 3 plant-based dietary patterns (overall, healthy, and unhealthy) with CVD incidence and all-cause mortality. Overall diet quality was low for all participants, and participants with the most plant-rich diets still regularly included animal-based foods. Incidence of CVD and all-cause mortality was the same among participants whose diets were most similar to a plant-based dietary pattern and among those whose diets were least plant-based. Among individual food groups, legumes were associated with a lower risk for CVD, while vegetable oils were associated with higher risk for CVD, and whole grains and sugar-sweetened beverages were associated with higher all-cause mortality. What do these findings mean? Plant-based diet index scores have gained popularity among researchers for their ability to characterize overall dietary patterns; however, their use may be limited in populations with minimal gradations in the plant richness of participants’ diets. Health benefits linked to plant-based diets may depend on the overall healthfulness of an individual’s diet and might require higher levels of adherence to a plant-based diet than what is typically practiced among those with the most plant-rich diets in this cohort of African Americans residing in the southern region of the US.