Re: Cochrane Review of Hibiscus Effects on Blood Pressure
Ngamjarus C, Pattanittum P, Somboonporn C. Roselle for hypertension in adults. Cochrane Database Syst Rev. Jan 20, 2010;(1):CD007894.
Hibiscus (Hibiscus sabdariffa), also
known as sour tea, red tea, red sorrel, flor de Jamaica, and roselle, is a
popular herbal tea in many parts of the world. Animal studies have demonstrated
that aqueous extracts of hibiscus flowers lower blood pressure in rats.
Clinical trials have demonstrated antihypertensive effects in adults with type 2
diabetes and those with moderate or mild hypertension, but more research is
needed for confirmation.1,2,3 The purpose of this review by the
Cochrane Collaboration was to examine the effect of hibiscus on blood pressure.
The reviewers included randomized controlled
trials (RCTs) with durations of 3-12 weeks that compared hibiscus to a placebo
or no intervention. The inclusion criteria required that the RCTs include
patients over the age of 18 with systolic blood pressures (SBP) and diastolic
blood pressures (DBP) equal or greater to 140 mm Hg and 90 mm Hg, respectively.
The primary outcome measures were changes in the trough and/or peak of SBP and DBP compared to the placebo
group or no intervention.
In June 2009, the authors searched the following
databases for relevant articles: the Database of Abstracts of Reviews of
Effectiveness (DARE), Cochrane Database of Systematic Reviews, Cochrane Central
Register of Controlled Trials (CENTRAL), MEDLINE (2005-2009), EMBASE
(2007-2009), Allied and Complementary Medicine Database (1985-May 2009), CINAHL
(1982-2009), BIOSIS (1969-2008), AGRICOLA (1970-May 2009), Food Science and
Technology Abstracts (1969-June 2009 week 1), International Pharmaceutical
Abstracts (1970-May 2009), and International Bibliographic Information on
Dietary Supplements (IBIDS). They also used other information resources,
including www.clinicaltrials.gov, the System for Information on Grey Literature
in Europe (OpenSIGLE), ISI Web of Knowledge, and hand searches of journals,
conference proceedings, and reference sections of published articles. The final
search was in September 2009.
Out of 159 records recovered in the literature
search, 26 were retrieved for review. Of those 26, 17 were duplicates. The
authors excluded two articles that did not include hypertensive patients, one
report that was not an RCT, and one paper that was an initial report of another
article. None of the remaining five articles met the inclusion criteria. Among
these, one used black tea as the control in hypertensive diabetics,1
two used ACE inhibitors as controls,2,3 and the other study used as
a control "ordinary" tea and only lasted for 15 days.4 An
abstract of a randomized, double-blind, placebo control study of 6 weeks
duration with pre- and mildly hypertensive subjects was not included because
the complete article had not yet been published, but it has become available in
its final form in 2010.5 All five of these studies found significant
reductions in SBP.
According to the authors, "No reliable
conclusions can be drawn about the benefit of Roselle [hibiscus] for either controlling or
lowering blood pressure in patients with hypertension compared to placebo or no
treatment." Nonetheless, clinical studies comparing hibiscus tea with drug
treatments and black (or "ordinary") tea (Camellia sinensis) have found beneficial effects in the treatment
of hypertension. Well-designed, placebo-controlled RCTs on the effects of
hibiscus tea on hypertension are needed.
—Marissa Oppel-Sutter, MS
References
1. Milot B. Antihypertensive effects of hibiscus
in patients with type II diabetes. HerbClip.
April 30, 2009. (No. 040191-375). Austin,
TX: American Botanical Council. Review
of The effects of sour tea (Hibiscus sabdariffa) on hypertension in
patients with type II diabetes by Mozaffari-Khosravi H, Jalali-Khanabadi B-A,
Afkhami-Ardekani M, Fatehi F, Noori-Shadkam M. J Human Hypertension.
2009(23):48-54.
2. Minigh J. Efficacy and tolerability of
hibiscus in patients with hypertension. HerbClip.
February 28, 2007. (No. 100263-323). Austin,
TX: American Botanical Council. Review
of Effectiveness and tolerability of a standardized extract from Hibiscus sabdariffa in patients with
mild to moderate hypertension: a controlled and randomized clinical trial by
Herrera-Arellano A, Flores-Romero S, Chavez-Soto MA, Tortoriello J. Phytomed. July 2004;11(5):375-382.
3. Oliff HS. Study finds hibiscus extract may
help control hypertension. HerbClip. February
28, 2007. (No. 020571-323). Austin,
TX: American Botanical Council. Review
of Clinical effects produced by a standardized herbal medicinal product of Hibiscus sabdariffa on patients with
hypertension. A randomized, double-blind, lisinopril-controlled clinical trial
by Herrera-Arellano A, Miranda-Sanchez J, Avila-Castro P, et al. Planta Med. 2007;73:6-12.
4. Webb D. Hibiscus tea lowers blood pressure -
clinical study. HerbClip. February
29, 2000. (No. 091399-171). Austin,
TX: American Botanical Council. Review
of The effect of sour tea (Hibiscus
sabdariffa) on essential hypertension by Faraji MH, Haji Tarkhani AH. J Ethnopharmacol. 1999;65(3):231-236.
5. Oppel-Sutter
M. Hibiscus tea may help lower blood pressure in mild hypertension. HerbClip. March 15, 2010. (No. 021066-396).
Austin, TX:
American Botanical Council. Review of Hibiscus
sabdariffa L. tea (tisane) lowers blood pressure in prehypertensive and
mildly hypertensive adults by McKay DL, Chen CY, Saltzman E, Blumberg JB. J Nutr. 2010;140(2):298-303.