Why do vegetarians have lower blood pressure?

It is well known that high blood pressure is a major risk factor for heart disease. Controlling blood pressure through lifestyle factors, such as diet and exercise, is key for avoiding heart problems.

But medical opinion has been split over whether a vegetarian diet is effective for reducing blood pressure. Different studies on how vegetarian diets influence blood pressure have reported conflicting results.

Vegetarians generally have lower BMIs and a lower risk of obesity than omnivores, probably because vegetarian diets have higher fiber and lower fat content than omnivorous diets. Because body weight and blood pressure are linked, this might partially explain the lowered blood pressure in vegetarians. However, other studies have found that a vegetarian diet lowers blood pressure regardless of body weight.

Another suggestion is that vegetarian diets are high in potassium and low in sodium, but again, some studies have disagreed over the impact this might have. Some studies have also found that alcohol consumption is lower in vegetarians, compared with the general population. Alcohol intake can influence blood pressure, but five of the seven clinical trials analyzed in this study were limited to participants who drank no more than moderate amounts of alcohol. Therefore, the results of this analysis were probably not influenced by alcohol intake.

Vegetarian diets are usually proportionally lower than omnivorous diets in saturated fatty acids and higher in polyunsaturated fatty acids - characteristics that are associated with lower blood pressure. And, finally, vegetarians usually have lower blood viscosity. This could affect their blood pressure.