HealthDay News — Vegetarians had lower blood pressure than their meat-eating counterparts, findings from a meta-analysis show.
Compared with omnivores, BP was an average of 4.8/2.2 mm Hg lower among vegetarians in controlled trials and 6.9/4.7 mm Hg lower in cross sectional studies (P<0.001 for all), Yoko Yokoyama, PhD, MPH, of the National Cerebral and Cardiovascular Center in Osaka, Japan, and colleagues reported in JAMA Internal Medicine.
“[S]uch diets could be a useful nonpharmacologic means for reducing blood pressure,” the researchers suggested.
Results of previous observational studies have shown an association between a vegetarian diet and hypertension rates, but results from controlled trials have been mixed.
To get a better understanding of the effect of eating a vegetarian diet on BP, Yokoyama and colleagues pooled data from seven controlled trials (n=311) and 32 cross-sectional observational studies (n=21,604). For the purposes of this study, vegetarian diets could include fish or rare consumption of other meat.
In both the controlled and cross-sectional studies, adherence to a vegetarian diet was associated with reductions in systolic and diastolic BP “similar to those observed with commonly recommended lifestyle modifications, such as adoption of a low-sodium diet or a weight reduction of 5 kg (11 lbs),” the researchers wrote.
These BP changes are approximately equivalent to half the magnitude of changes achieved with pharmaceutical therapies such as ACE inhibitors for people with hypertension, they added.
The researchers offered some potential explanations for the mechanism of action underlying the changes, including lower BMI in vegetarians due to eating foods that are higher in fiber, and less dense and fattening; higher levels of potassium, a nutrient inversely associated with BP; a lower proportion of saturated fats and a higher proportion of polyunsaturated fats; more vegetable protein; and the possibility that vegetarians have less viscous blood.
“Consumption of vegetarian diets is associated with lower BP,” the researchers wrote. “Further studies are required to clarify which types of vegetarian diets are most strongly associated with lower BP.”
Study limitations included a high degree of heterogeneity in the observational studies, small sample sizes, lack of adjustment for lifestyle factors and between diet variations.