Abstract
We aimed to examine the association between adherence to plant-based diets (PBDs) and the risk of mortality among the general population. Relevant investigations were identified through PubMed, Scopus, Embase, and ISI Web of Knowledge. Data were pooled using a random-effects or a fixed-effects model. Twelve prospective cohort studies with 42,697 deaths among 508,861 participants were included. The hazard ratios (HRs) for the highest compared to the lowest category of adherence to the PBDs were 0.90 (95% confidence interval [CI]: 0.82, 0.99; I2 = 91%, n = 12) for all-cause and 0.77 (95% CI: 0.70, 0.86; I2 = 36%, n=8) for coronary heart disease (CHD) mortality. Among PBDs subtypes, there was an inverse association between healthy plant-based 0.92 (95% CI: 0.88, 0.96; I2 = 0%, n = 2), Pesco-vegetarian 0.81 (95% CI: 0.70, 0.92; I2 = 0%, n = 2), and Pro-vegetarian 0.74 (95% CI: 0.55, 0.88; I2 = 61.2%, n = 2) diets and the risk of all-cause mortality. A vegetarian diet was also associated with lower risk of mortality due to cardiovascular 0.92 (95% CI: 0.85, 0.99; I2 = 0%, n=5) and CHD 0.76 (95% CI: 0.68, 0.85; I2 = 35%, n = 7). Our findings show the potential protective role of PBDs against chronic disease mortality. As there were certain limitations in some of the studies included in this systematic review and meta-analysis, further research is necessary to confirm our findings.
Generated Summary
This meta-analysis, following PRISMA guidelines, investigates the relationship between plant-based diets (PBDs) and mortality risk. The study included 12 prospective cohort studies, analyzing data from 508,861 participants and 42,697 deaths. Data were pooled using fixed-effect or random-effects models, with hazard ratios (HRs) calculated for various dietary patterns. The research explores the associations between different types of PBDs, including vegetarian, vegan, and semi-vegetarian diets, and the risk of all-cause, cardiovascular disease (CVD), coronary heart disease (CHD), and cerebrovascular disease mortality. The study’s goal was to determine the potential protective role of PBDs against chronic disease mortality in the general population, while acknowledging limitations in some of the included studies.
Key Findings & Statistics
- All-cause mortality: Greater adherence to PBDs (highest vs. lowest category) was associated with a lower risk (HR: 0.90, 95% CI: 0.82, 0.99; I² = 90.7%, Pheterogeneity < .001).
- Pesco-vegetarian diet: Inverse association with all-cause mortality (HR: 0.81, 95% CI: 0.70, 0.92).
- Healthy PDI: Associated with lower all-cause mortality (HR: 0.92, 95% CI: 0.88, 0.96).
- Pro-vegetarian diet: Inverse association with all-cause mortality (HR: 0.74, 95% CI: 0.55, 0.88).
- Vegetarian diet: Associated with lower CVD mortality (HR: 0.92, 95% CI: 0.85, 0.99).
- CHD mortality: Inverse association between vegetarian diet and lower risk (HR: 0.76, 95% CI: 0.68, 0.85; I² = 35%, Pheterogeneity = .16).
- PBDs and CVD Mortality: The results of highest vs. lowest category did not show significant association between the PBDs and CVDs mortality (HR: 0.90, 95% CI: 0.79, 1.02; I² = 78%, Pheterogeneity < .001).
- CHD Mortality and Vegetarian Diet: Our analyses based on the type of diets showed inverse association between the vegetarian diet and lower risk of CHD (HR: 0.76, 95% CI: 0.68, 0.85; 1² = 35%, Pheterogeneity = .16)
Other Important Findings
- Subgroup analyses revealed that the PBDs were associated with lower all-cause mortality risk if studies were from the USA.
- The results were significant if analyses were controlled for energy intake.
- Vegetarian diet was significantly associated with lower risk of CHD mortality.
- No association was found between PBDs and cerebrovascular mortality.
- PBDs were not associated with mortalities from cancers and other causes.
Limitations Noted in the Document
- The study notes that some findings are based on the meta-analyses of only two studies, which should be interpreted with caution.
- The clarity and detail in the diets of the control groups in some studies (e.g., non-vegetarian and meat-eater) were limited.
- The assessment of diet in some studies was self-reported using general questions, which increases the chance of measurement error.
- Publication bias was not assessed for some outcomes.
- Heterogeneity remained high in some cases, potentially due to dissimilar populations, sample sizes, and methods of exposure assessment.
Conclusion
The findings indicate an inverse association between PBDs and the risk of all-cause and CHD mortality, highlighting the importance of newly developed plant-based indexes in the assessment of plant diets. The study also notes a protective effect of a usual vegetarian diet on CVD and CHD mortality. However, due to the limitations and the need for further investigations, it is suggested that future prospective and clinical investigations are needed to elucidate further findings and to fill in the major gaps in this area. These findings support the idea that expanding the use of PBDs as a line of research for the potential amelioration of chronic disease morbidity and mortality may lead to important public health implications.