A Review: Garlic Effects on the Cardiovascular System-Juniper Publishers
JUNIPER PUBLISHERS-OPEN ACCESS JOURNAL OF CARDIOLOGY & CARDIOVASCULAR THERAPY
Coronary Artery Disease (CAD) is one of the leading
causes of morbidity and mortality in the world. Detection as well as
modification of risk factors for cardiovascular disease (CVD) has been
the topics research over several decades. Multiple drugs have been
studied and used in clinical practice with people seeking “natural”
alternatives. When evaluating for optimal treatment options and the
multiple risk factors associated CAD (e.g. diabetes, hypertension,
etc.), garlic can play a prominent role. Studies have shown promising
results in treating hypertension, altering the lipid profile, prevention
and even treatment of coronary atherosclerosis and its systemic
anti-oxidant properties.
Garlic also has positive effects outside the
cardiovascular system (e.g. immune system). It can be used stand-alone
or as an adjunct to current medical therapy. No clinically significant
side effects have been reported, thus providing a safe treatment option
to be considered. Coronary Artery Disease (CAD) is one of the leading
causes of morbidity and mortality in the world. Detection as well as
modification of risk factors for cardiovascular disease (CVD) has been
the topics research over several decades. Multiple drugs have been
studied and used in clinical practice with people seeking “natural”
alternatives. Some well-known alternatives include pomegranate juice,
green tea, and garlic [1-3]. Our focus will be on the utility of garlic.
Multiple myths and beliefs over thousands of years exist where garlic
is a key element in treatment and prevention of illness (e.g. common
cold) as well as increasing strength and endurance.
It was even used as a performance enhancer in ancient
Olympics. In recent years, garlic has been a major area of focus in
prevention and treatment of CAD and associated risk factors. We will
review the role garlic has played in the modification of hypertension,
hyperlipidemia, inflammatory markers and coronary artery calcium [3-7].
Garlic can provide an alternative to conventional medication without
significant side effects.
Lipid Profile
Multiple studies have implemented garlic’s effect of
the lipid profile. Of all the components of the lipid panel, well known
are the effects of LDL, triglycerides, total cholesterol and their role
in CAD. In a meta-analysis by Reinhart et al examined the role of garlic
on reduction of total cholesterol, driven mostly by reduction in
triglycerides (TAG) [8]. In fact, the component most potent for creating
a proinflamatory state is the remnant lipoprotein cholesterol [9].
Remnant lipoproteins (RLPs) are products of partially catabolized
chylomicrons and very-low-density lipoprotein, from which some
triglycerides have been removed, that are found to be highly
arythmogenic.
Remnants are known to cross the endothelial barrier
and due to their larger size, they carry 5 to 20 times as much
cholesterol per particle as LDL [10]. Remnant (apo A1 remnant ratio)
association with short and intermediate termmortality was shown to be a
significant predictor, especially in women above 50 years of age [11].
In a study by de Vries et al. [12], chylomicrons were shown to be more
potent in causing inflammation when compared to hypertriglyceridemia
[12,13]. Of note, Matsuo et al showed remnant lipoprotein levels being
linked to coronary plaque vulnerability, which is characterized by high
necrotic and low fibrotic components [14].
Thus, remnant lipoproteins are well known and
becoming more established as risk factors for CAD [13]. Nakamura et al.
[15] was also able to establish the role of insulin resistance as also
contributing to postprandial hyperlipidemia, especially in those with
CAD, thus possibly requiring more aggressive treatment of such states
[15,16]. Well known at this time the various treatment options and
preventative measure for hyperlipidemia (e.g. diet, exercise, statins,
fibrates, etc.)
Hypertension is also another well-known cardiovascular
disease risk factor. Garlic has shown to have a role in treatment
of hypertension. Reid et al. [17] in the AGE at Heart trial was
able to establish a direct link of garlic on central and peripheral
hypertension; as an adjunct or stand-alone treatment. Mean
blood pressure was significantly reduced by 5.0±2.1mmHg
(P=0.016) systolic, and in responders by 11.5±1.9mmHg
systolic and 6.3±1.1mmHg diastolic compared to placebo
(P<0.001) [17,18]. Thus, establishing a role in the reduction of
both central and peripheral blood pressure.
Xiong et al. [19] in a meta-analysis on 7 randomized,
placebo controlled trials since 2014 was able to establish a
similar link on the role of garlic on hypertension. This metaanalysis
revealed a significant lowering effect of garlic on both
systolic BP (WMD: -6.71mmHg; 95% CI: -12.44 to -0.99; P=0.02)
and diastolic BP (WMD: -4.79mmHg; 95% CI: -6.60 to -2.99; P
< 0.00001). Hosseini et al. [20] was able to establish a similar
link in addition to the effect on lipid profile as well as antidiabetic
effect. Despite this link, more research is required to
establish garlic as a stand along treatment of hypertension. At
this time, it can be used as an adjunct to conventional means.
Garlic has also to have a role in prevention and treatment
of coronary atherosclerosis. Multiple randomized trials were
able to demonstrate a significant reduction in Coronary Artery
Calcium (CAC) progression [4]. This is demonstrated through
its direct role on the atherosclerotic process [21,22]. In a study
by Budoff et al. & Ahmadi et al. [21,22], aged garlic extract
supplemented with B vitamins, folic acid and L-arginine
had a positive role in not only reducing atherosclerosis but
improvement in oxidative biomarkers and vascular function.
Matsumoto et al. [23] was able to establish the role of
aged garlic extract and its role in coronary plaque. The % low
attenuated plaque (LAP) change in the study was significantly
reduced in the AGE group compared with the placebo
group (-1.5%±2.3% compared with 0.2%±2.0%, P=0.0049).
Multivariable linear regression analysis found a beneficial
effect of AGE on %LAP regression (β: -1.61; 95% CI: -2.79, -0.43;
P=0.008) [23]. Thus, demonstrating the inhibitory role on the
progression of non-calcified plaque. Recently, Madaj et al.
[24] demonstrated garlic’s positive effects on coronary artery
calcium, to supplement those earlier studies. Karagodin et al.
[25] after evaluation of the Atherosclerosis Monitoring and
Atherogenicity Reduction Study was able to show reduction of
cardiovascular risk after use of garlic.
Twelve-month treatment lowered 10-years prognostic
risk of coronary artery disease by 13.2% in men (P=0.005),
and by 7.1% in women (P=0.040). Ten-year prognostic risk of
acute myocardial infarction and sudden coronary death waslowered by 26.1% in men (P=0.025) [25]. Studied here was also
the progression of carotid atherosclerosis in asymptomatic
men which can one can indirectly infer its effect on coronary
artery atherosclerosis. Mahdavi-Roshan et al. [26] were able
to demonstrate lack of progression of carotid intima media
thickness with the use of garlic. After 3months of taking garlic
tablets, CIMT values had minor variations (0.009±0.007mm
reduction from baseline), while in the placebo group, an
increase in CIMT values was observed (0.04±0.01mm increase
from baseline). Zeb et al. & Ahmadi et al. [27,28] were also able
to demonstrate the use of garlic in the prevention of coronary
artery disease. Thus, garlic has been shown to have positive
effects on coronary atherosclerosis either as a stand-alone
treatment or adjunct to conventional therapy.
Garlic has been found in studies to have a prominent role
in affecting inflammatory markers. Despite its systemic antioxidant
effects, we will limit our discussion to its effects on
the cardiovascular system. This link has been demonstrated
predominantly by decreased levels of CRP and Il-17A27, thus
allowing garlic to have a direct role on the atherosclerotic
process [21,22]. In a study by Budoff et al & Ahmadi et al.
[21,22], aged garlic extract supplemented with B vitamins,
folic acid and L-arginine had a positive role in not only reducing
atherosclerosis but improvement in oxidative biomarkers and
vascular function. Ried et al. [17] in the AGE at Heart trial were
also able to demonstrate a reduction in inflammatory markers.
TNFα was reduced in the garlic group compared to placebo
with borderline significance (P=0.05), while changes in IL-
1β were not significant, but greater reduction was observed
in the garlic group [17]. Results to date are very promising in
establishing this relationship, but further work is needed to
validate and expand on the progress made on the link between
garlic and its anti-oxidant properties.
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