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Vegetarian diets associated with lower BP
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Adults who consume a vegetarian diet have lower BP, according to results of a new meta-analysis.
Yoko Yokoyama, PhD, MPH, from the National Cerebral and Cardiovascular Center in Osaka, Japan, and colleagues analyzed and pooled data from seven clinical trials (n=311; mean age, 44.5 years) and 32 observational studies (n=21,604; mean age, 46.6 years) that included vegetarian diets as an exposure or intervention and also reported mean difference in BP as an outcome.
In the seven clinical trials, consumption of vegetarian diets was associated with a reduction in mean systolic BP (–4.8 mm Hg; 95% CI, –6.6 to –3.1; P<.001) and mean diastolic BP (–2.2 mm Hg; 95% CI, –3.5 to –1; P<.001) compared with consumption of an omnivorous diet. In the 32 observational trials, consumption of vegetarian diets was also associated with decreases in mean systolic BP (–6.9 mm Hg; 95% CI, –9.1 to –4.7; P<.001) and mean diastolic BP (–4.7 mm Hg; 95% CI, –6.3 to –3.1; P<.001).
The effect size of lowering BP by consuming a vegetarian diet is approximately the same as adopting a low-sodium diet or reducing weight by 5 kg, and is approximately half of that observed with pharmacologic therapy, Yokoyama and colleagues wrote.
According to the researchers, the following are possible explanations for the observed associations:
- Adults who consume vegetarian diets typically have lower BMI and lower risk for obesity compared with omnivores, but studies that controlled for body weight have still found a BP-lowering effect from vegetarian diets.
- Vegetarian diets are high in potassium; high intake of potassium has demonstrated increased vasodilation and glomerular filtration rate and decreased renin level and renal sodium absorption, among other factors.
- Vegetarian diets may be lower in sodium, although research on this issue is conflicting.
- Alcohol consumption may be lower among adults who consume vegetarian diets compared with omnivorous diets. However, five of the seven clinical trials analyzed excluded adults whose alcohol consumption was more than modest.
- Compared with omnivorous diets, vegetarian diets are lower in saturated fatty acids and higher in polyunsaturated fatty acids, both of which are associated with lower BP.
- Vegetarian diets are associated with reduced blood viscosity, which may impact BP.
- Consuming vegetable protein is inversely associated to BP.
“The findings of the present study are consistent with those of a previous review of observational studies. They also accord with those of the Dietary Approaches to Stop Hypertension study, which was based on the observation that consumption of vegetarian diets was associated with a reduced risk of hypertension and found that a diet rich in vegetables and fruits, along with other dietary changes, reduced systolic BP and diastolic BP,” the researchers wrote.
Further research is needed to determine which vegetarian diets are most strongly linked to lower BP.
Disclosure: The researchers report no relevant financial disclosures.
Perspective
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Binh An P. Phan, MD, FACC, FNLA
There are a number of dietary interventions that have been shown to lower BP. The results of this meta-analysis of vegetarian diets support findings from prior research that have demonstrated that similar diets that are low in sodium and rich in fruits and vegetables can lower BP. Vegetarian diets often overlap with some of the previously studied diets, such as the DASH diet, which also emphasizes consumption of fruits, vegetables, legumes and low-fat dairy products.
The findings of this meta-analysis should be taken with caution given that much of the data were drawn from 32 observational studies and only 311 participants were from seven controlled trials with significant heterogeneity reported in the observational studies. Also, many of the observational studies did not adjust for factors that could affect BP, including alcohol intake and physical activity. The results of this meta-analysis reinforce what I do in my clinical practice in terms of recommending a diet low in sodium and saturated fats, and high in fruits and vegetables. More research is needed to evaluate the specific BP and CV benefit of vegetarian diets.
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