Vegetarians tend to have lower blood pressure than the general population, but it hasn’t been clear whether their diet or their lifestyle guards them against hypertension.
A review of previously published studies shows that diet provides the protection. “It’s the diet itself, and it is clearly the diet of choice for people who want to get their blood pressure under control,” said Dr. Neal D. Barnard, president and founder of the Physicians Committee for Responsible Medicine and co-author of the report. Barnard, an M.D. and a nutritionist, concluded that a person who suffers from hypertension and has yet to switch to a vegetarian diet is “really trying to fight their condition with one arm tied behind their back.”
About 65 million American adults have high blood pressure, according to the National Heart, Lung, and Blood Institute. Hypertension is often called the “silent killer” because it usually has no symptoms but leads to increased risk for heart disease, congestive heart failure, stroke and kidney failure. Barnard and committee nutritionist Susan Berkow analyzed 80 scientific studies, including observational studies of individuals on vegetarian diets compared with non-vegetarians and randomized, controlled trials in which outcomes of people who switch to a plant-based diet were compared with control subjects.
Some of the best observational data, according to the report, come from studies involving Seventh-Day Adventists, who advocate an alcohol-free, tobacco-free, vegetarian lifestyle.  One study involving California Adventists found that vegetarians have about half the prevalence of hypertension compared to non-vegetarian Adventists. When hypertensives were defined as those taking medication intended to reduce their blood pressure, a nearly threefold difference in the prevalence of hypertension was seen between the groups.
Overall, the randomized controlled trials included in the review found that blood pressure is lowered when animal products were replaced with vegetable products in both people with normal blood pressure and those who are hypertensive. To understand the blood-pressure-lowering effects of a plant-based diet, the authors examined changes in body weight and intake of specific food groups and nutrients.
Studies show that vegetarians tend to be slimmer, on average, which may help explain their lower incidence of hypertension. A vegetarian diet also is significantly lower in saturated fat, reducing the viscosity, or thickness, of the blood. Blood becomes “less like oil, more like water,” Barnard explained. And because vegetarian diets are generally high in vegetables, people who follow this diet consume more potassium than those who eat a diet of meat and vegetables. The analysis cites two reviews involving a total of 52 randomized clinical trials showing potassium supplementation significantly lowered blood pressure in people with normal and elevated blood pressure.
Barnard hopes the review will prompt more doctors to recommend a vegetarian diet. Many are reluctant to do because they fear that patients won’t stick with it, but there’s no reason to believe patients would be less likely to go vegetarian than to comply with other diets, he said.
“They may not hit the mark 100 percent, but they’d do much better if a doctor recommended it,” he said.
-Nutrition Reviews.
Dr. Keith and Laurie Nemec comments on Vegetarian Diet Lowers Blood Pressure:
There is no question about what diet is best—there never has been. As this study shows, when a plant based diet is adopted, blood pressure decreases. There are many reasons for this but let us look at three of them.
1.    Weight loss
2.    Thinner blood
3.    Potassium to sodium ratio increases
Weight Loss: It has been seen in every study that when a plant based diet high in vegetables is consumed, people lose weight. Since weight is a major stress factor in increasing the risk of heart disease, diabetes and cancer, it just is common sense to eat a plant based diet to reduce your weight and your risk of all disease.
Thinner Blood: Blood must move at a high speed to keep you healthy. The faster the blood moves, the more oxygen and nutrients you get into the cells and the more waste products and toxins you get out of the cells. The average American, because of their high animal based diet, have blood “sludge”. This means their blood is too thick causing it to move slower through the blood vessels and also causing a decrease in oxygen and nutrients into the cells and waste products and toxins out of the cells. Let us use this analogy. If your blood speed was a highway, the speed for total health would be 700 miles per hour whereas the average American’s speed would be around 60 miles per hour. How do you increase the speed of the blood? Thin it out with an exclusive living/raw plant based diet. How do you clog it up? Thicken it with a diet of meat, chicken, fish, eggs, milk, butter and cheese. The choice is yours on how fast you want to drive on the highway to Total Health.
Potassium to Sodium Ratio:   The ideal ratio of potassium to sodium in a person with the highest level of health is 5:1. The average animal product consuming American has the reverse ratio of 5:1 sodium to potassium. So, how do you get your ratio to the ideal 5:1 potassium to sodium ratio? Eat a vegetable based diet. Vegetables have a 5:1 potassium ratio so when you consume them in high quantities in the raw, uncooked state they bring balance, healing and health to your body.