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According to Alternative Medicine: The Definitive Guide, herbs commonly used to help treatment of hypertension include garlic, mistletoe, olive leaves, hawthorn berries, and periwinkle.1 Of these, the two that were found to have the most research done on them were garlic and hawthorn.
Garlic
Blood pressure reducing properties of
garlic have been linked to its hydrogen sulphide production and allicin content
liberated from alliin and the enzyme alliinase which has angiotensin II
inhibiting and vasodilating effects, as shown in animal and human cell studies.19 The beneficial effect of garlic, or Allium sativum, of lowering
blood Chagan et al. report a meta-analysis of eight clinical trials, six of which were placebo-controlled, that did show a significant reduction in BP with garlic, but patient compliance with the supplement was not assessed in any of the trials. These authors also point out that garlic has been associated with decreased platelet aggregation and increased bleeding events.3 Knox & Gaster remind readers of the recognizable odor and taste of garlic that make the supplement hard to blind to patients in trials. They report two trials that reported BP lowering with garlic, but also point out the many known side effects of garlic, including gastrointestinal upset and even some as serious as myocardial infarction and small intestinal obstruction. Garlic also interacts with the P450 enzyme system that metabolizes many drugs. Therefore, it probably interacts with many medications, and this could lead to further adverse effects.7 Ried et al. published a meta-analysis of eleven randomized, controlled trials that showed garlic had a hypotensive effect, more so in hypertensive patients, than placebo. However, they admit the populations used in the studies involved were heterogenous and the dose of garlic used was not standardized. They suggest future trials use standardized doses to determine whether a dose-effect relationship between garlic and BP exists.19 Another meta-analysis done by Reinhart et al. showed BP lowering effects of garlic, but only in hypertensive patients. These authors also point out that since garlic is not a controlled substance, contaminants and other biologically active substances could be found in the supplements that the patients in these trials receive.17 Although garlic has much research behind it as a hypotensive agent, the quality of the research must be questioned. The serious reported side effects cannot be ignored either. More on garlic can be found here.
Hawthorn
Hawthorn, also known as Crataegus monogyna, is a substance that is usually thought to help treat congestive heart failure, but it might have possible hypotensive effects as well. These effects have been hypothesized to act by activating endothelial-derived relaxing factor and inhibiting phosphodiesterase. Knox & Gaster reported that one RCT of hawthorn showed no evident BP lowering effect after ten weeks of supplementation.7 This is the only study in the literature, and consisted of low doses and a small number of patients.4 Hawthorn has been shown to have vasodilatory effects in animals and in vitro studies.7 Therefore, a larger, higher quality, trial of hawthorn may be beneficial to see if these effects are true in humans. More on hawthorn can be found here. |
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Copyright 2009 Creighton University |
pressure
(BP) has been reported in many studies. However, the majority of these studies
enroll small numbers of patients. 