A vegetarian diet may help lower blood pressure, researchers who reviewed data from 39 previous studies said Monday.
The researchers suggested that a vegetarian diet could be an alternative to drugs for people whose blood pressure is too high -- a condition known as hypertension and one that is a risk factor for heart disease and other problems. About a third of Americans have high blood pressure.
Seven clinical trials, with 311 participants, and 32 observational studies, including 21,604 people, were analyzed by researchers from Japan and the Physicans Committee for Responsible Medicine in Washington, which advocates for plant-based diets.
Blood pressure is usually expressed in terms of the systolic pressure over diastolic pressure and is measured in millimeters of mercury. For most people, a reading of 120/80 or less is considered normal.
In the study, published in the Journal of the American Medical Assn. Internal Medicine, the analysis indicated a systolic difference of 4.8 mm of mercury lower for vegetarians than for omnivores in the clinical, or controlled, trials, and 6.9 mm in the observational studies -- in which people chose their diets. For the the diastolic measure, the difference was 2.2 mm and 4.7 mm, respectively.
Those differences are similar to those often seen with such modifications as changing to a low-salt diet or losing about 10 pounds, the researchers said.
And, they added, they're about half the difference found with medications.
The study didn't point to specific aspects of the vegetarian diet that could be at work. But vegetarians typically have a lower body mass index than omnivores and their diets often are lower in saturated fatty acids and higher in potassium, the researchers said.
They said additional studies would be needed to sort out which vegetarian diets work best.
One of the researchers, Dr. Neal Barnard of the Physicians Committee for Responsible Medicine, said he was not surprised at the findings.
Some people still may need medications, and blood pressure is affected by other factors, including genetics, he said.
But people need specific dietary advice, and doctors need to help issue it. "A vegetarian diet is a very good step, but it's not the only step to take," he said.
"Two-thirds of American adults are heavier than they should be," Barnard said. "It's time for us to stop playing around as if this doesn't matter."