Vegan diet does not significantly reduce BP in adults
No association exists between a vegan diet and lower blood pressure (BP) measurements as compared with omnivorous alternatives, a study has found. The effect of a vegan diet in adults is similar to that by portion-controlled diets and those recommended by medical societies.
“In individuals with a systolic BP ≥130 mm Hg, a vegan diet could result in an additional 4-mm Hg reduction in BP,” the researchers noted in a subgroup analysis.
Pooled data from the meta-analysis of 11 randomized controlled trials (RCTs) included 983 participants. A vegan diet, compared with less restrictive dietary approaches, did not lead to a significant reduction in systolic (–1.33 mm Hg, 95 percent CI, –3.50 to 0.84; p=0.230) or diastolic (–1.21 mm Hg, –3.06 to 0.65; p=0.203) BP. [Am J Med 2019;132:875-883.e7]
In a prespecified subgroup analysis of studies with baseline systolic BP ≥130 mm Hg, a vegan diet reduced both systolic (mean, –4.10 mm Hg, –8.14 to –0.06; p=0.047) and diastolic (mean, –4.01 mm Hg, –5.97 to –2.05; p=0.000) BP.
These findings are not consistent with another meta-analysis of seven clinical trials and 32 observational studies (n=311 participants), which found that vegetarian diets resulted in a 5–7-mm Hg decrease in systolic BP as compared with omnivorous diets. [JAMA Intern Med 2014;174: 577]
That meta-analysis included only two clinical trials that evaluated a vegan diet. One showed no significant difference between the effect of a vegan and an omnivorous diet on BP, whereas the other was not a randomized trial, and each group was selected from a different geographical location, potentially leading to biased findings. [Prev Med 1999;29:87-91; Am J Clin Nutr 2009;89:1588S-1596S]
“Our data suggest that the effect of vegan diets on BP is similar to that of diets recommended by medical societies or portion-controlled diets,” the researchers said. “These diets, which result in a decreased dietary sodium intake, lower systolic BP by 1–4 mm Hg in normotensive individuals and by 5.5–7.8 mm Hg in hypertensive individuals.” [Cochrane Database Syst Rev 2017;4:CD004022]
Throughout the studies, participants were advised to reduce their consumption of red meat, increase their intake of vegetables and lose weight. Such changes correlated with improved systolic BP and could explain the lack of statistical significance in the trend favouring a vegan diet in the subgroup of studies with unsupervised control diets, according to the researchers. [Adv Nutr 2016;7:76-89]
The present study searched Medline, Embase, Central and ClinicalTrials.gov for records comparing a vegan diet with any less restrictive diet and reporting pre- and postintervention systolic and diastolic BP. Two reviewers independently screened abstracts for RCTs in individuals aged ≥18 years. The PRISMA guidelines were used to select 11 clinical trials from 1,673 records. Data synthesis was conducted using a random-effects model.
“There are no randomized clinical trials evaluating the role of a vegan diet for blood pressure control in hypertensive patients, and research in this area may prove beneficial given the benefits of vegan diets on other cardiovascular risk factors,” the researchers said.