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- Pomegranate (Punica granatum, Lythraceae)
- Blood Pressure
- Systematic Review/Meta-analysis
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Date:
02-28-2017 | HC# 021761-563
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Re: Meta-analysis Reports that Pomegranate Juice Consumption Causes Clinically Meaningful Reductions in Blood Pressure
Sahebkar
A, Ferri C, Giorgini P, Bo S, Nachtigal P, Grassi D. Effects of pomegranate
juice on blood pressure: a systematic review and meta-analysis of randomized
controlled trials. Pharmacol Res. January
2017;115:149-161.
Elevated
blood pressure increases risk for cardiovascular disease and may be a worthy
target of novel therapeutics. A diet rich in fruits and vegetables could confer
a protective effect against cardiovascular disease due to the presence of bioactive
compounds such as polyphenols, which, among other activities, may lower blood
pressure. Pomegranate (Punica granatum,
Lythraceae) juice contains polyphenols and may help alleviate cardiovascular
disease risk; however, studies investigating pomegranate juice report
inconsistent results. This systematic review and meta-analysis analyzed
randomized controlled trials of pomegranate juice for potential effects on
blood pressure.
The
databases Scopus, Medline, MagIran, and Scientific Information Database were
searched from their starting date to December 12, 2014, with no language
restrictions. Search terms included "randomized controlled trial" OR
randomized OR placebo, "blood pressure" OR hypertension OR
anti-hypertensive OR hypotension OR hypotensive, and pomegranate OR Punica. Studies included were randomized
controlled trials that researched the effects of pomegranate juice on blood
pressure, included "sufficient" data on baseline and endpoint
parameters (which apparently included blood lipid levels), and had a minimum two-week
treatment period. Trials that were not clinical studies or did not include
controls, lacked adequate baseline or follow-up data, used a pomegranate
product that was not juice or not orally dosed, or used another fruit juice or
potentially bioactive substance as a control were excluded.
Data
collected from trials included the first author's name, year of publication, study
site, numbers of subjects, treatment dose and length of administration, and
study subjects' age, gender, body mass index, total cholesterol and low-density
lipoprotein and high-density lipoprotein cholesterol concentrations,
triglyceride and glucose concentrations, systolic and diastolic blood pressure
(SBP and DBP, respectively), and fasting glucose concentrations. Potential bias
was measured according to the Cochrane criteria, which include factors such as adequacy
of sequence generation, allocation concealment, blinding, and discussion of
dropouts.
The
literature search yielded 986 studies, of which 930 could be excluded by
examination of their titles and abstracts, following the criteria listed above.
Out of the studies left, 48 were excluded after further examination, leaving
eight trials for the systematic review and meta-analysis. When data from all
were combined, 322 subjects were in a pomegranate group and 252 were in a control
group. Trials were published from 2004 to 2014. Two studies were single-blind,
placebo-controlled, double-arm trials, one was a placebo-controlled, crossover
design (whose subjects were therefore in both the pomegranate and control
groups), and the remaining studies were randomized, double-blind,
placebo-controlled trials. Duration of treatment ranged from two weeks to 18
months. Patients had a range of health issues or cardiovascular risk factors,
including hypertension, ischemic coronary heart disease, carotid artery
stenosis, one or more cardiovascular risk factors and high carotid intima-media
thickness, type 2 diabetes, and/or hemodialysis. Healthy subjects also were included.
Quality
of bias was investigated, and it is stated that "almost all studies"
had a low-bias risk. A few studies had missing data on randomization processes,
allocation concealment, or blinding. Additionally, there was no evidence of
significant publication bias. There were significant decreases in both SBP (weighted
mean difference [WMD], −4.96 mmHg; 95% confidence intervals [CI], −7.67 to −2.25;
P<0.001) and DBP (WMD, −2.01 mmHg; 95% CI, −3.71 to −0.31; P=0.021) in those
consuming pomegranate juice. SBP was significantly reduced in both subjects who
consumed pomegranate for > 12 weeks (WMD, −4.36 mmHg; 95% CI, −7.89 to −0.82;
P=0.016) and in those consuming juice for < 12 weeks (WMD, −5.83 mmHg; 95%
CI, −10.05 to −1.61; P=0.007). The decrease in DBP was significant only in
those consuming juice < 12 weeks (WMD, −3.93 mmHg; 95% CI, −6.80 to −1.06; P=0.007).
The
decrease in SBP was also significant in both subjects consuming > 240 ml/day
(WMD, −3.63 mmHg; 95% CI, −6.62 to −0.63; P=0.018) and in those consuming <
240 ml/day (WMD, −11.01 mmHg; 95% CI, −17.38 to −4.65; P=0.001). Reductions in
DBP were not statistically significant at either dosage concentration
(evidently because of the smaller number of subjects in each group). According
to a meta-regression analysis, there were no associations between the SBP and
DBP changes and the dosage or duration of pomegranate juice consumption.
In
conclusion, this meta-analysis suggests that pomegranate juice consumption is
efficacious for lowering blood pressure. Cited literature indicates that a
population-level effect of this size can meaningfully reduce cardiovascular
disease. It is suggested that this effect may be due to flavonoids present in
the juice; however, any measurements of this parameter are omitted here.
Discussed limitations include the small number of studies and subjects,
variation among studies, and differences in subject health. Further study in hypertensive
populations would clarify the efficacy of pomegranate juice consumption on
lowering blood pressure.
—Amy C. Keller, PhD
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