Effects of herbs and spices on blood pressure: a systematic literature review of randomised controlled trials.

: Hypertension is a major risk factor for cardiovascular disease, affecting 1 billion people worldwide. Literature suggests some herbs and spices have cardiovascular benefits, such as decreasing blood pressure; yet evidence is inconsistent. This article reviewed randomized controlled trials investigating effects of herbs and spices on blood pressure in normotensive, pre-hypertensive and hypertensive participants. Ovid Medline, Embase, Biological abstracts, CINAHL and Cochrane Collaboration were systematically searched. After inclusion and exclusion criteria were applied, nine articles were included for analysis. Overall, three of the nine studies reported statistically significant results, including one of the two studies on hypertensive participants and two of the six studies on pre-hypertensive participants. The remaining study was conducted on normotensive participants and reported no change in blood pressure. There is evidence to suggest certain herbs and spices can reduce blood pressure in a hypertensive and pre-hypertensive population and may not induce hypotension in a normotensive population.