The effectiveness of Hibiscus sabdariffa in the treatment of hypertension: a systematic review.

ABSTRACT

Introduction: Hypertension is a common global health problem with

significant mortality and morbidity. Hibiscus sabdariffa is a plant

known in many countries and is consumed as hot and cold drinks In

addition to its use in folk medicine; it has been suggested as treatment

for many conditions including hypertension.

Objectives: The objectives of this review were to examine the

evidence of effectiveness and safety of hibiscus in the treatment of

hypertension.

Methods: We searched several medical databases {MEDLINE, EMBASE,

CINAHL, Cochrane Central Register of Controlled Trials, and the

specialized register of the Cochrane Hypertension Group and the general

engine Google) to January 2009.

We included randomized controlled trials that had examined

Hibiscus’s effectiveness and safety in the treatment of primary

hypertension in adults. Two authors independently selected the trials

for the review, extracted the data, and critically appraised the

included studies.

Results: Four trials, with a total of 390 patients, met our

inclusion criteria. Two studies compared Hibiscus sabdariffa to black

tea; one study compared it to captopril and one to lisinopril. The

studies found that Hibiscus had greater blood pressure reduction than

tea but less than the ACE-inhibitors. However, all studies, except one,

were short term and of poor quality with a Jadad scoring of < 3 and

did not meet international standards.

Conclusion: The four randomized controlled studies identified in

this review do not provide reliable evidence to support recommending

Hibiscus sabdariffa for the treatment of primary hypertension in adults.

[C] 2009 Elsevier GmbH. All rights reserved.

ARTICLE INFO

Keywords: Hibiscus sabdariffa Hypertension

INTRODUCTION

High blood pressure is a global health problem with significant

magnitude of morbidity and mortality, it has been estimated that 1

billion individuals all over the world suffer from hypertension causing

up to 7.1 million deaths per year, which is about 13% of total death

worldwide, and it is one of the ten factors contributing to the global

burden of disease (Brown 1997).

Among the pharmacological agents used to treat hypertension are

angiotensine converting enzyme (ACE) inhibitors, and diuretics (Neal et

al. 2000; Gallagher et al. 2006). However, there are still needs for

additional agents for resistant hypertension, and also for

non-pharmacological measures that might be encouraged at population

level.

Hibiscus sabdariffa is one potential non-pharmacological treatment.

In folk medicine, the calyces’ infusion is used for the treatment

of several conditions including high BP.

Anthocyanins and proanthocyanidins compounds, detected in abundance

in the aqueous infusion of the Hibiscus calyces, could be the bioactive

compounds responsible for lowering the blood pressure based on earlier

studies which proved the antihypertensive effects of anthocyanins

through the inhibition of angiotensine II converting enzyme and hence a

vasodilatation effect (Jonadet et al. 1990) in addition to its diuretic

effect and the increased concentration of urinary sodium while

maintaining normal potassium levels (Onyenekwe et al. 1999).

Objectives

The objectives of this review are to determine the effectiveness

and safety of Hibiscus sabdariffa in the treatment of patients with

pre-hypertension or hypertension ([greater than or equal to] 140/90),

with the specific outcome of reduction in systolic blood pressure (SBP),

diastolic blood pressure (DBP) or both.

Methods

We included randomized controlled studies which compare Hibiscus to

placebo, to other herbal or pharmacological preparation or to no other

intervention in the treatment of adults (18-70 years), with the

diagnosis of pre-hypertension 130-139/85-89 or primary hypertension of

stage I or II according to the JCT classification (Chobanian et al.

2003), irrespective of patients’ gender or co-morbidity.

Search Strategy

We searched the several databases (MEDLINE, EMBASE, CINAHL,

Cochrane Central Register of Controlled Trials, Cochrane library for

systematic reviews, the specialized register of the Cochrane

Hypertension Group, ClinicalTrials.gov and the general search engine

Google) from commencement until January 2009. Using the search words

(Hibiscus, Hibiscus sabdariffa, Sour tea, Roselle, Red sorrel, Karkade,

Jamaica, Flor de Jamaica, herbal tea, herbal medicine) and in

combination with (high blood pressure, elevated blood pressure,

hypertension, pre-hypertension, mild hypertension), there was no

limitation to language. We reviewed the reference list for any potential

study and we contacted authors when further information was enquired, we

did not conduct hand search.

Identification of included studies

All titles and abstracts retrieved by electronic searching were

screened independently by two reviewers and the studies which clearly

did not meet the inclusion criteria were excluded. Copies of the full

text of potentially relevant references were obtained and their

eligibility was assessed independently by two reviewers. Differences

between reviewers were resolved by discussion.

Data extraction and studies evaluation

The data were extracted and categorized by two authors including

number of patients, type of comparison to hibiscus (placebo or other

herbal or pharmacological agent), duration of treatment and the primary

outcome which was the reduction in the SBP, DBP or both, expressed as

Means [+ or -] SD. The trials were assessed for methodological quality

using Jadad Score (Jadad et al. 1996) in addition evidence of allocation

concealment and adequacy of addressing incomplete data were assessed.

Results

The literature search retrieved 523 titles of which we reviewed ten

potential abstracts and the full text was retrieved for six studies

(Haji Faraji and Haji Tarkhani 1999; Herrera-Arellano et al. 2004, 2007;

Mozaffari-Khosravi et al. 2008; Diane et al. 2008; Wright et al. 2007),

four of which met the inclusion criteria. The description of the

selected studies is included in (Table 1) and the results of the studies

are included in (Table 2).

Table 1

Results of the identified studies.

First Author (Year Participants Stage of HT Experimental

of publication) according treatment

to the

JCPTTH-7th

Report

E C

Haji Faraji. M et 31 23 Stage II ST

al. (1999)

Herrera-Arellano. 53 37 Pre-HT & HS extract

A et al. (2004) stage I

Herrera-Arellano. 100 93 Stage I & HS

A et al. (2007) Stage II standardized

extract

Mozaffari-Khosravi. 27 26 Pre-HT & ST

H et al. (2008) stage I

First Author (Year of publication) Control treatment Duration

Haji Faraji. M et al. (1999) BT 2 WEEKS

Herrera-Arellano. A et al. (2004) Captopril 4 WEEKS

Herrera-Arellano. A et al. (2007) Lisinopril 4 WEEKS

Mozaffari-Khosravi. H et al. (2008) BT 4 WEEKS

First Author (Year ResultsDSBP

of publication) (Means[+ or-] SD)DDBP (Means [+ or -] SD)

E

Haji Faraji. M et DSBP (17.6[+ or -]11.3)DDBP(10.9[+ or -]7.6)

al. (1999)

Herrera-Arellano. DSBP (14.2[+ or -]11.8)DDBP(11.2[+ or -]6.9)

A et al. (2004)

Herrera-Arellano. DSBP (17.1[+ or -]10.0)DDBP(12.0[+ or -]7.0)

A et al. (2007)

Mozaffari-Khosravi. DSBP (15.0[+ or -]7.5)DDBP(4.3[+ or -]12.3)

H et al. (2008)

First Author (Year ResultsDSBP A/E

of publication) (Means[+ or-] SD)DDBP (Means [+ or -]SD)

C

Haji Faraji. M et (6.3[+ or -]6.6)(3.5[+ or -]5.2) NR

al. (1999)

Herrera-Arellano. A

et al. (2004) (16.4[+ or -]9.6)(13.1[+ or -]7.2) NR

Herrera-Arellano. A

et al. (2007) (23.3[+ or -]70)(15.4[+ or -]60) NR

Mozaffari-Khosravi.

H et al. (2008) (8.4[+ or -]11.0)(4.6[+ or -]11.8) NR

Key: E=Experimental; C=Control; HT=Hypertension;

Pre-HT=Prehypertention; ST=Sour tea; HS=Hibiscus sabdariffa; BT=Black

tea; A/E=Adverse event; NR=Not recorded; JCPTTH=Joint national

committee of prevention detection and treatment of hypertension 7th

report; DSBP/DDBP=difference in systolic/diastolic blood pressure.

Table 2

Evaluation of validity of selected studies.

Trial Author (year) Participants’ Allocation Blinding

Sequence Concealment

Generation

Haji Faraji and Haji Unclear Unclear No.(Only

Tarkhani (1999) Participants

were blinded)

Herrera-Arellano. A Yes, (Random Not done No, (two

et al. (2004) number table) different

preparation for

was used

experimental and

control groups.

Herrera-Arellano. A Yes, (Random Not done Yes, Double

et al.(2007) number table) blinding

(author confirmation)

Mozaffari-Khosravi. Yes, (Random Not done Unclear

H et al. (2008) number table) (Participants

were blinded

but no

information

about assessors

blinding)

Trial Author (year) Incomplete Other Biases Jadad

Data Score

Addressed?

Haji Faraji and Haji No, No report of Zero

Tarkhani (1999) (unbalanced adverse outcome.

dropout from No baseline

the characteristics

experimental for study and

and control control groups

groups, to verify

dropout is due adequacy of

to high blood randomization.

pressure, no

intention to

treat

analysis)

Herrera-Arellano. A No, There is 2

et al. (2004) (unbalanced singificant

dropout from baseline

the imbalance

experimental between the two

and control groups in SBP,

groups, PP, stage of

dropout, is hypertension and

mostly, due to BMI which

bitter taste directly

of hibiscus, influence the

no intention outcome.

to treat

analysis)

Herrera-Arellano. A No, (12% of No other obvious >3

et al.(2007) participants biases.

were excluded Tolerability was

from the addressed

analysis due

to

non-adherence

to adherence

to treatment.

No intention

to teat

analysis.)

Mozaffari-Khosravi. Yes, (10% of There is 1

H et al. (2008) participants significant

from each baseline

group were imbalance

excluded from between the two

the analysis, groups in SBP,

however this DBP, and PP,

did not affect which directly

the balance influence the

between the outcome. Some

two groups participants in

control have got

normal BP

One study was excluded because only the abstract was published and

the authors did not provide us with information about the methodology of

the study (Diane et al. 2008) and the other study was a review of

studies mostly done on animals (Wright et al. 2007).

The results of the 2 studies of hibiscus against black tea suggest

a modest reduction of systolic and diastolic blood pressure; the two

studies that compared hibiscus to ACE-inhibitors showed similar declines

in blood pressure, but less than that of ACE-inhibitors. However,

Meta-analysis was not done due to the poor methodology of the studies

and the low Jadad score (Table 2). Table 3 shows the methods for

hibiscus preparation and use.

Table 3

Methods of preparation and use of hibiscus.

Study (Year Methods and Methods of use of

Publication) conditions of hibiscus by the trial

preparation of Participants

Hibiscus

Haji Faraji and Method of preparation two spoonfuls of blended

Haji Tarkhani of Hibiscus was tea in one glass of boiled

(1999) not mentioned in the water boiled for 20-30 min,

trial. to take once a day

for 15 days

Herrera-Arellano et The collected Preparation of an

al. (2004) material was infusion is by add the

dried under contents of the envelope

dark conditions to 0.51 of boiling

at room water and let stand

temperature and for 10min, and drink

then ground in daily before breakfast

an electric for 4 Weeks

mill to obtain

particles of