Abstract
Vegan diets are increasing in popularity and have beneficial effects on glycemia and blood lipids, but the evidence is inconclusive regarding their effect on blood pressure. The purpose of this study was to review the effect of vegan diets on blood pressure in adults. METHODS: We searched MEDLINE, EMBASE, CENTRAL, and ClinicalTrials.gov for records that compared a vegan diet with any less restrictive diet and reported pre- and postintervention systolic and diastolic blood pressures. Two reviewers independently screened abstracts for randomized, controlled clinical trials in individuals ≥ 18 years of age and older. We used the PRISMA guidelines to select 11 clinical trials from 1673 records. Data synthesis was performed through a random-effects model. RESULTS: The pooled data included 983 participants. Compared with less restrictive diets, a vegan diet did not result in a significant change in systolic (-1.33 mm Hg; 95% confidence interval [CI], -3.50-0.84; P = .230) or diastolic (-1.21 mm Hg; 95% CI, -3.06-0.65; P = .203) blood pressure. A prespecified subgroup analysis of studies with baseline systolic blood pressure ≥ 130 mm Hg revealed that a vegan diet resulted in a mean decrease in the systolic (-4.10 mm Hg; 95% CI, -8.14 to -0.06; P = .047) and diastolic (-4.01 mm Hg; 95% CI, -5.97 to -2.05; P = 0.000) blood pressures. CONCLUSION: The changes in blood pressure induced by a vegan diet without caloric restrictions are comparable with those induced by dietary approaches recommended by medical societies and portion-controlled diets.
Generated Summary
This meta-analysis of randomized controlled trials investigates the impact of vegan diets on blood pressure in adults. The study utilized MEDLINE, EMBASE, CENTRAL, and ClinicalTrials.gov to identify relevant studies, following PRISMA guidelines for selection. The primary outcome was the postintervention systolic blood pressure, with secondary outcomes including postintervention diastolic blood pressure and within-group changes. The analysis used a random-effects model to synthesize data from 11 clinical trials involving 983 participants, comparing vegan diets with less restrictive diets. The study aimed to determine the effects of vegan diets, in light of their increasing popularity and potential health benefits, specifically regarding blood pressure management. The research was conducted to address the existing gap in literature concerning the effect of vegan diets on blood pressure and to provide insights into their potential role in managing cardiovascular health.
Key Findings & Statistics
The analysis of 11 clinical trials with 983 participants revealed the following:
- Compared to less restrictive diets, a vegan diet did not significantly change systolic blood pressure (-1.33 mm Hg; 95% CI, -3.50 to 0.84; P = .230) or diastolic blood pressure (-1.21 mm Hg; 95% CI, -3.06 to 0.65; P = .203).
- A subgroup analysis of studies with baseline systolic blood pressure ≥ 130 mm Hg showed that a vegan diet resulted in a mean decrease in systolic (-4.10 mm Hg; 95% CI, -8.14 to -0.06; P = .047) and diastolic (-4.01 mm Hg; 95% CI, -5.97 to -2.05; P = 0.000) blood pressures.
- The pooled data included 983 participants with a mean age of 44.2 ± 22.8 years.
- Vegan diets were compared with lacto-ovo-vegetarian diets in 1 study and with 3 types of omnivorous diets.
- The use of antihypertensive therapy was variable: ≥ 50% of participants used antihypertensives in 3 studies and <50% used antihypertensives in 4 studies.
- Meta-regression identified the baseline systolic blood pressure (β coefficient -0.433; P = .0002) and use of antihypertensive therapy (β coefficient 0.095; P = .0400) as sources of heterogeneity.
- Interestingly, in studies where the baseline systolic blood pressure was ≥130 mm Hg, a vegan diet resulted in a mean decrease of -4 mm Hg in both the systolic and diastolic blood pressures; there was no heterogeneity in this subgroup (I² = 0%; P = .560 and P = .978 for heterogeneity for both outcomes).
Other Important Findings
- The changes in blood pressure induced by a vegan diet without caloric restrictions are comparable with those induced by dietary approaches recommended by medical societies and portion-controlled diets.
- The study assessed pre- and post-intervention systolic and diastolic blood pressures and changes from baseline.
- The study’s results did not vary significantly when comparing the random-effects model with the fixed-effects model, or in one-study-removed analysis.
- The authors evaluated the effect of a vegan diet on the change between the pre- and postintervention blood pressure measurements.
- The study included the analysis of pooled changes in blood pressure by dietary type, source population, and other clinical characteristics.
Limitations Noted in the Document
- The lack of allocation concealment and lack of blinding of outcome assessors were potential sources of bias in several studies.
- Blinding of participants was not possible due to the nature of the intervention.
- Many studies had a limited sample size.
- The composition of a vegan diet is not standardized and can vary widely among individuals and between geographical locations.
- A significant portion of the included studies were performed on diabetic participants.
- The study did not assess the change in blood lipids, glycemic outcomes, body mass index, or waist circumference.
Conclusion
The meta-analysis concludes that vegan diets do not significantly alter blood pressure compared to less restrictive diets, although a subgroup analysis showed promise for those with higher baseline systolic blood pressure. The study indicates that vegan diets can lead to a reduction in both systolic and diastolic blood pressure in individuals with elevated baseline systolic blood pressure (≥ 130 mm Hg). The authors suggest that the effects of vegan diets on blood pressure are similar to those of diets recommended by medical societies or portion-controlled diets. However, the study highlights that there are no randomized clinical trials evaluating the role of a vegan diet for blood pressure control in hypertensive patients. The research suggests that, given the benefits of vegan diets on other cardiovascular risk factors, future studies could prove beneficial. The study’s findings underscore the potential for vegan diets as a dietary approach to blood pressure management, especially in individuals with elevated blood pressure. The results align with the growing interest in plant-based diets for health. The authors recommend further research to understand the full impact of vegan diets on cardiovascular health. The findings contribute to the ongoing discussion about the benefits of dietary interventions for managing blood pressure.