Plant-based diets and soy lower blood pressure
As many as 67 million American adults, or about one in three adults, have high blood pressure and just as many have prehypertension—blood pressure numbers that are higher than normal—but not yet in the high blood pressure range. Elevated blood pressure increases risk for heart disease and stroke and is a contributing factor in nearly 1,000 deaths per day in the United States.
Diet and lifestyle have significant effects on blood pressure. Obesity, high salt intake, and excessive alcohol use are associated with increased blood pressure. Physical activity and diets rich in the mineral potassium can help to keep blood pressure low.
A number of studies have shown that people eating vegetarian diets have lower blood pressure. To better understand this relationship, a team of Japanese researchers analyzed findings from a total of 39 observational and clinical studies that had looked at the relationship of vegetarian diets to blood pressure. In the clinical trials, adoption of a vegetarian diet led to a decrease of 4.8 points in systolic blood pressure and a 2.2 point decrease in diastolic blood pressure. In the 32 observational studies, which included a total of 21,604 participants, vegetarians had on average systolic BP that was 6.9 points lower, and diastolic blood pressure that was 4.7 points lower, than their nonvegetarian counterparts.
A vegetarian diet was as effective as commonly prescribed lifestyle changes to lower blood pressure, such as a reduction in salt intake or weight loss. It was also half as effective as drug therapy in lowering blood pressure which suggests that a vegetarian diet could reduce the need for medication.
It isn’t clear why vegetarian diets lower blood pressure. The lower body weights that are typical of vegetarians may be one reason, although it is only part of the explanation. Even after controlling for difference in body weight, vegetarian diets were still associated with lower blood pressure. Vegetarians also tend to eat more soy products which could also be part or the explanation. Studies have shown that soy protein lowers systolic blood pressure by about 2.5 points and diastolic blood pressure by about 1.5 points.
Yokoyama Y, Nishimura K, Barnard ND, et al. Vegetarian Diets and Blood Pressure: A Meta-analysis. JAMA Intern Med 2014;