Evidence suggests plant-based diets reduce blood pressure

By Pooja Toshniwal PahariaMay 17 2023Reviewed by Lily Ramsey, LLM

In a recent study published in the Current Hypertensive Reports Journal, researchers performed a systematic review to evaluate the impact of consuming plant-origin foods on an individual’s blood pressure (BP).

Study: Plant-Based Diets Reduce Blood Pressure: A Systematic Review of Recent Evidence. Image Credit: TatjanaBaibakova/Shutterstock.com

Background

Hypertension, or high blood pressure, increases the risk of developing cardiovascular diseases like heart attacks and stroke.

Diet is a modifiable factor that can be tailored to lower blood pressure, and therefore, research must be conducted to identify foods that would maximally benefit hypertensive patients.

Large-scale studies such as the EPIC-Oxford trial and the Adventist Health Study-2 (AHS-2) with nearly 10,000 participants reported lower BP readings among plant-based food consumers than meat-eaters.

Similar observations have been reported in the Nurses’ Health Study Phases I and II (NHS-I and II), the Health Professionals Follow-up Study (HPFS), and the Coronary Artery Risk Development among Young Adults (CARDIA) study.

Evaluating the impact of diet on blood pressure could inform decision-making and improve the standard of care for hypertensive individuals.

About the study

In the present systematic review, researchers assessed the impact of plant-based foods on BP.

Databases such as PubMed, Scopus, and Web of Science were searched for randomized controlled trials (RCTs) on the effects of plant-sourced diets on blood pressure. Only studies published from 2020 onward in English were included in the analysis.

Search terms such as “plant-based diet,” “hypertension’, “Mediterranean diet,” and “blood pressure” were used with Boolean operators such as “OR” and “AND” inserted between the search terms.

The data search was based on the guidelines for Systematic Reviews and Meta-Analyses (PRISMA). Data on the underlying blood pressure-lowering components of plant-origin diets were also analyzed.

The team excluded articles on the design, rationale, and baseline variables of an ongoing or future study, reviews, book chapters, conference papers, and clinical practice statements.

In addition, baseline cross-sectional studies; studies where the diet was not the only study exposure; animal studies; non-RCT studies; studies with diets that were not precisely plant-sourced; studies where plant-sourced diets were not the primary study exposures; studies where results were not discriminated among groups; and studies where the diet was not the primary exposure were excluded from the analysis.

Results

Initially, 8,422 records were identified, of which only 39 eligible studies were considered for the final analysis.

Plant-origin diets included different diets with a high content of whole grains, vegetables, and fruits, including the vegetarian diet and its modifications (including lacto-ovo-vegetarian and lacto-vegetarian diets); the Mediterranean (Med) diet; the healthy Nordic diet; and the Dietary Approach to Stop Hypertension (DASH) diet [including the Japanese cuisine-based DASH (J-DASH)].

Most RCTs reported that plant-based diets lowered BP values more than animal-based diets. A recent meta-analysis, including 32.0 cross-sectional design studies and >20,000 individuals, showed lower average BP values among individuals consuming vegetarian foods than omnivorous foods.

Likewise, a recently published meta-analysis including 187.0 individuals from five RCTs documented a lowering of systolic BP (SBP) and diastolic BP (DBP) by 5.47 mmHg and 2.3 mmHg, respectively, among individuals consuming lacto-ovo-type vegetarian diets, with high and moderate quality of evidence for the changes in SBP and DBP values, respectively.

Another meta-analysis, including 856 individuals from 15 RCTs, showed a significant reduction in SBP and DBP of 2.7 and 1.7 mmHg, respectively, related to vegetarian diets than plant- and animal-based diets. Vegans demonstrated a greater reduction in SBP  (3.1 mmHg) than lacto-ovo-vegetarians (1.8 mmHg). Similarly, among vegans, DBP values were reduced by 1.9 mmHg.

DASH diets also lowered BP compared to control diets, particularly among hypertensive patients and African American individuals, with reductions in SBP and DBP values of 5.5 and 3.8 mmHg, respectively, and high certainty of evidence.

In a meta-analysis of four prospective, eight cross-sectional studies involving >30,000 individuals and 6,342 patients with metabolic syndrome (MetS), BP showed a significant but inverse relationship with consuming Mediterranean diets (relative risk, 0.9). Similar results were obtained in ≥three meta-analyses with moderate-quality evidence.

Further, a meta-analysis, including 420 participants from three RCTs, showed that Nordic diets lowered SBP and DBP values by 4.5 and 2.3 mmHg, respectively, compared to the comparator diets.

Recent trials such as PREDIMED and PREDIMED-Plus reported that adhering to Mediterranean diets decreased the need to escalate antihypertensive treatment among individuals consuming two antihypertensive drugs and showed cardioprotective effects.

Vitamin C (ascorbic acid) increases the levels of tetrahydrobiopterin, a critical cofactor for endothelial nitric oxide synthase (eNOS) activity to stimulate stimulates endothelium-derived nitric oxide (EDNO) synthesis.

Potassium may exert antihypertensive effects by altering the sodium-potassium adenine triphosphates (ATPase) activity, inducing cellular hyperpolarization, reducing calcium ion concentration, enhancing vasomotion, and inhibiting sodium absorption.

Polyphenols in foods such as thyme, olive, artichoke, and beetroot increase vasomotion, preserve endothelial redox status, and enhance eNOS hydroxylation.

Omega-3 fatty acids, particularly docosahexaenoic acid (DHA) and alpha-linolenic acid (ALA), inhibit cyclooxygenases and nicotinamide adenine dinucleotide phosphate hydrogen (NADPH) oxidase 4 (Nox 4) activity, reduce superoxide production, and improve vasodilator responses.

Conclusions

Based on the study findings, plant-sourced diets, particularly the Dash and Med diets, favoring vegetable, fruit, and whole grain consumption and limiting sodium, sugar, processed, and red meat intake, can lower blood pressure and have better cardiometabolic outcomes than animal-based diets.