Abstract
BACKGROUND: Dietary guidelines recommend substituting animal protein with plant protein, however, the ideal ratio of plant-to-animal protein (P:A) remains unknown. OBJECTIVES: We aimed to evaluate associations between the P:A ratio and incident cardiovascular disease (CVD), coronary artery disease (CAD), and stroke in 3 cohorts. METHODS: Multivariable-adjusted Cox proportional hazard models were used to estimate hazard ratios (HRs) for CVD outcomes among 70,918 females in the Nurses' Health Study (NHS) (1984-2016), 89,205 females in the NHSII (1991-2017) and 42,740 males from the Health Professionals Follow-up Study (1986-2016). The P:A ratio was based on percent energy from plant and animal protein and assessed using food frequency questionnaires every 4 y. RESULTS: During 30 y of follow-up, 16,118 incident CVD cases occurred. In the pooled multivariable-adjusted models, participants had a lower risk of total CVD [HR: 0.81; 95% confidence interval (CI): 0.76, 0.87; P trend < 0.001], CAD (HR: 0.73; 95% CI: 0.67, 0.79; P trend < 0.001), but not stroke (HR: 0.98; 95% CI: 0.88, 1.09; P trend = 0.71), when comparing highest to lowest deciles of the P:A ratio (ratio: ∼0.76 compared with ∼0.24). Dose-response analyses showed evidence of linear and nonlinear relationships for CVD and CAD, with more marked risk reductions early in the dose-response curve. Lower risk of CVD (HR: 0.72; 95% CI: 0.64, 0.82) and CAD (HR: 0.64; 95% CI: 0.55, 0.75) were also observed with higher ratios and protein density (20.8% energy) combined. Substitution analyses indicated that replacing red and processed meat with several plant protein sources showed the greatest cardiovascular benefit. CONCLUSIONS: In cohort studies of United States adults, a higher plant-to-animal protein ratio is associated with lower risks of CVD and CAD, but not stroke. Furthermore, a higher ratio combined with higher protein density showed the most cardiovascular benefit.