Abstract
Purpose Although emphasis has recently been placed on the importance of diet high in plant-based foods, the association between plant-based diet and long-term risk of overall and cause-specific mortality has been less studied. We aimed to investigate whether plant-based diet was associated with lower death risk. Methods This prospective cohort study used data from the US National Health and Nutrition Examination Survey. Diet was assessed using 24 h dietary recalls. We created three plant-based diet indices including an overall plant-based diet index (PDI), a healthful plant-based diet index (hPDI), and an unhealthful plant-based diet index (uPDI). Deaths from baseline until December 31, 2015, were identified. Multivariable-adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated using Cox regression. Results We documented 4904 deaths among 40,074 participants after a median follow-up of 7.8 years. Greater adherence to PDI was associated with lower risk of overall (HR comparing extreme quintiles 0.80, 95% CI 0.73, 0.89, Ptrend <0.001) and cancer-specific (HR=0.68, 95% CI 0.55, 0.85, Ptrend <0.001) mortality. These inverse associations remained for hPDI and overall mortality with a HR of 0.86 (95% CI 0.77, 0.95, Ptrend=0.001), but not for cancer or CVD mortality. Conversely, uPDI was associated with higher risk of total (HR = 1.33, 95% CI 1.19, 1.48, Ptrend <0.001) and CVD-specific (HR = 1.42, 95% CI 1.12, 1.79, Ptrend=0.015) mortality. Conclusions Increased intake of a plant-based diet rich in healthier plant foods is associated with lower mortality risk, whereas a plant-based diet that emphasizes less-healthy plant foods is associated with high mortality risk among US adults.
Generated Summary
This study, a prospective cohort study, utilized data from the US National Health and Nutrition Examination Survey (NHANES) to examine the association between plant-based diets and the risk of all-cause and cause-specific mortality among US adults. The research employed 24-hour dietary recalls to assess dietary intake and created three plant-based diet indices: an overall plant-based diet index (PDI), a healthful plant-based diet index (hPDI), and an unhealthful plant-based diet index (uPDI). Deaths were tracked from baseline until December 31, 2015, and multivariable-adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated using Cox regression models. The study aimed to investigate whether plant-based diets were associated with lower death risk, considering potential non-linear relationships between the dietary indices and mortality risk. The analysis included 40,074 participants with a median follow-up of 7.8 years. The study considered the potential non-linear relationships between dietary indices and mortality risk by using restricted cubic splines. Sensitivity analyses were also conducted to minimize reverse causation and explore the robustness of the findings.
Key Findings & Statistics
- The study documented 4904 deaths among 40,074 participants after a median follow-up of 7.8 years.
- Greater adherence to PDI was associated with lower risk of overall mortality (HR comparing extreme quintiles 0.80, 95% CI 0.73, 0.89, Ptrend <0.001) and cancer-specific mortality (HR=0.68, 95% CI 0.55, 0.85, Ptrend <0.001).
- These inverse associations remained for hPDI and overall mortality with a HR of 0.86 (95% CI 0.77, 0.95, Ptrend = 0.001), but not for cancer or CVD mortality.
- Conversely, uPDI was associated with higher risk of total mortality (HR = 1.33, 95% CI 1.19, 1.48, Ptrend <0.001) and CVD-specific mortality (HR = 1.42, 95% CI 1.12, 1.79, Ptrend = 0.015).
- PDI scores at baseline ranged from a median of 46 in the lowest quintile to 60 in the highest quintile.
- Participants with higher scores of PDI or hPDI were more likely to be non-Hispanic whites, older, better educated, and had a higher ratio of family income to poverty.
- The association of hPDI with overall mortality (HR 0.86, 95% CI 0.77–0.95, Ptrend=0.001) was found.
- Greater adherence to uPDI was associated with higher risk of both overall (HR 1.33, 95% CI 1.19–1.48, Ptrend <0.001) and CVD (HR 1.42, 95% CI 1.12–1.79, Ptrend=0.015) mortality.
- The study found a weak inverse association between two food components (nuts and vegetables) and mortality risk.
- The HR for overall mortality per 10-point increase in PDI was 0.85 (0.80-0.90).
- The HR for overall mortality per 10-point increase in hPDI was 0.89 (0.84-0.94).
- The HR for overall mortality per 10-point increase in uPDI was 1.17 (1.11-1.23).
Other Important Findings
- The study found a linear, decreasing trend for overall PDI in the risk of overall mortality.
- Multivariable splines for hPDI showed a non-linear decreasing trend in total mortality risk with borderline significance.
- The analysis of food groups included in PDI showed a weak inverse association between nuts and vegetables and the risk of total mortality.
- The study found no differential associations of PDI, hPDI, and uPDI with risk of total death, or death from cancer or CVD according to age, sex, race/ethnicity, education level, ratio of family income to poverty, marital status, smoking, alcohol drinking, physical activity, BMI, and diabetes.
Limitations Noted in the Document
- The study relied on self-reported dietary data using 24-hour recalls, which can lead to misclassification of dietary intake.
- Residual confounding could not be completely ruled out despite adjusting for a wide range of risk factors.
- The observational nature of the study design limits the ability to determine causality.
- The findings may not be generalizable to other countries due to the use of a nationally representative sample from the United States.
Conclusion
The study’s findings strongly support the recommendation to shift towards diets rich in plant-based foods and lower in less-healthy plant foods and certain animal products, highlighting the potential benefits for health and longevity. The research underscores the importance of distinguishing between healthful and unhealthful plant-based foods, as the former was associated with reduced mortality risk while the latter was linked to increased risk, particularly for CVD. The study supports the growing body of evidence suggesting that dietary patterns significantly impact health outcomes. The study’s findings are also consistent with prior research, particularly the non-linear relationships between dietary patterns and mortality risk. The research’s conclusions emphasize the potential benefits of plant-based dietary patterns, with lower mortality risk associated with increased adherence to the overall and healthful plant-based diet indices. The inverse association between PDI and cancer-specific mortality further supports the benefits of the plant-based diet. In contrast, the study highlights the health risks associated with diets that emphasize less healthy plant foods, as reflected by the higher mortality risk linked to the unhealthful plant-based diet index. The study’s outcomes emphasize the need for promoting dietary guidelines and interventions that focus on increasing the intake of plant foods while decreasing the consumption of less healthy plant foods and certain animal-based foods. The findings also contribute to the ongoing discourse on the effects of diet on overall health and longevity.