There is little scientific evidence to support the claim that vinegar is good for high blood pressure.
One Promising Study
One study published in the journal Bioscience, Biotechnology, and Biochemistry suggested that the acetic acid found in vinegar substantially lowered the blood pressure of rats that were given the dietary vinegar over a prolonged period. This claim has never been tested in humans causing the scientific community to question the validity of the vinegar blood pressure connection. [Kondo, 2694
Scientific Community Speaks
Though the study was promising, no such studies have been conducted on human subjects. In addition, scientific opinion such as that of the European Food Safety Authority does not substantiate these claims based on the fact that acetic acid's rapid absorption rate directly following consumption coupled with how quickly it clears the circulation system makes it highly unlikely to have a sustained effect on blood pressure. ["EFSA Panel on Dietetic Products" 2006]
As promising as the preliminary study is in regards to vinegar's relationship with blood pressure, it is clear that further human studies are necessary to support this evidence.