Objectives: Increasing intake of plant-based foods and reducing intake of animal foods have been recommended for chronic disease prevention. However, not all plant- or animal-based diets exert the same health effects due to their various compositions. We aim to assess the quality of plant- vs. animal-based diet in relation to mortality among US adults.
Methods: Using dietary data collected from a nationally representative sample of 29,113 US adults from the National Health and Nutrition Examination Survey (NHANES) 1999-2010, we created a comprehensive Diet Quality Index (cDQI) to distinguish the quality of plant- and animal-based dietary components. Higher intake of healthful plant- or animal-based components received higher scores whereas higher intake of less healthful components received lower scores. Mortality from all causes, cardiovascular diseases (CVD), and cancer were obtained from the National Death Index. Cox proportional hazard models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) after multivariable adjustments.
Results: During a median follow-up of 7.8 years, 2,860 total deaths occurred, including 726 CVD deaths and 671 cancer deaths. Compared to individuals in the lowest quartile, those in the highest quartile of cDQI had 27% lower all-cause mortality (HR=0.73, 95% CI: 0.62-0.87; p-trend=0.001) and 37% lower cancer mortality (HR=0.63, 95% CI: 0.43-0.92; p-trend=0.03). After controlling for animal-based components, higher quality of plant-based components remained significantly associated with lower all-cause mortality (Q4 vs. Q1: HR=0.74; 95% CI: 0.62-0.89, p-trend<0.001) and cancer mortality (Q4 vs. Q1: HR=0.62; 95% CI: 0.43-0.91, p-trend=0.02) whereas no associations were found for the animal-based components. The lower mortality associated with plant-based diet was stronger among individuals with comorbidities at baseline (all-cause mortality: HR=0.69, 95% CI: 0.57-0.83; p-trend<0.0001; CVD mortality: HR=0.66, 95% CI: 0.45-0.98; p-trend=0.04; cancer mortality: HR=0.44, 95% CI: 0.24-0.80; p-trend=0.003).
Conclusion: Improving the quality of plant-based dietary components may play a more important role in reducing mortality than improving the quality of animal-based ones, especially among individuals with chronic health conditions.