Advances in Biological Chemistry, 2011, 1, 29-33 ABC
doi:10.4236/abc.2011.12005 Published Online August 2011 (http://www.SciRP.org/journal/abc/).
Published Online August 2011 in SciRes. http://www.scirp.org/journal/ABC
The effects of consumption of raw garlic on serum lipid level,
blood sugar and a number of effective hormones on lipid and
sugar metabolism in hyperglycemic and/or hyperlipidemic
individuals
——Benefit of raw garlic consumption
M. Mahmoodi1*, S. M. Hosseini Zijoud1, G. H. Hassanshahi2, M. A. Toghroli1, M. Khaksari3,
M. R. Hajizadeh1, E. Mirzajani4
1Department of Biochemistry, Faculty of Medicine, Rafsanjan University of Medical Sciences, Rafsanjan, Iran;
2Molecular Medicine Research Center, Rafsanjan University of Medical Sciences, Rafsanjan, Iran;
3Physiology Research Center, Kerman University of Medical Sciences, Kerman, Iran;
4Department of Biochemistry, Faculty of Medicine, Rasht University of Medical Sciences, Rasht, Iran.
Received 2 July 2011; revised 4 August 2011; accepted 11 August 2011.
ABSTRACT
Diabetes mellitus is one of the worldwide largest
growing metabolic diseases. In this study the effects of
consumption of raw garlic on serum lipid level, blood
sugar and a number of effective hormones on lipid
and sugar metabolism (thyroid hormones and insulin)
in individuals either with high level of blood sugar or
lipid were investigated. Eighty five volunteers having
following clini cal history enrolled in the study: Group
1: having blood sugar more than 126 mg/dl (30 vol-
unteers); Group 2: having cholesterol higher than 245
mg/dl (30 volunteers); Group 3: having blood sugar
over 126 mg/dl and cholesterol more than 245 mg/dl
(25 volunteers). In group 1, there wasn’t a significant
differences between biochemical factors before and
after garlic consumption, whereas, in the second group
after 6 weeks of garlic consumption a decline in cho-
lesterol (P < 0.001), FBS and TG (P < 0.01) was
observed but HDL-C (P < 0.001) was increased. Six
weeks after termination of garlic consumption, cho-
lesterol (P < 0.001), FBS and TG (P < 0.05) were in-
creased and HDL-C (P < 0.01) was decreased. In the
third group, total cholesterol (P < 0.001), FBS (P <
0.01) and HbA1c decreased while HDL-C was in-
creased. Other factors, including thyroid hormones
(T3, T4), TSH and insulin showed no significant alte-
ration. In conclusion our results shown that raw gar-
lic consumption can reduce the FBS and Lipid in hy-
perglycemic and/or hyperlipidemic individuals.
Keywords: Garlic; Serum Lipid Level; Blood Sugar;
Hormones; Hyperglycemic; Hyperlipidemic
1. INTRODUCTION
Elevated lipid and sugar levels are amongst the most
important complications in cardiovascular disorders and
diabetes. Diabetes mellitus is known as the most grow-
ing metabolic disease that characterized by altered car-
bohydrate, lipid and protein metabolism [1], and in par-
allel with advancing in knowledge on the heterogeneity
of this disorder, the need for more appropriate therapy
increases [2]. Increasing level of lipid leads to cardio-
vascular diseases and stroke. The underlying mechanism
is increased LDL cholesterol, which further undergoes
oxidative modification in the presence of free radicals
[3]. The decrease LDL level with raised HDL cholesterol
play important role against these complications. Due to
the highly costs for synthetic drugs, probable side effects
of this drugs and also restrictions in use of these drugs,
during recent years scientists and researcher trying to
substitute herbal plant and some natural component in
these plants for treatment of disease.
It is well established that consumption of fruit and
vegetables prevents some diseases [4]. Among vegeta-
bles, garlic is one of the most important ones [5,6]. Gar-
lic (Allium sativum) is a member of the Liliaceae family,
which is one of the most popular herbs used worldwide
to reduce various risk factors associated with several
diseases [7]. It has been reported that garlic and onions
are effective in preventing cardiovascular diseases due to
their hypocholesterolemic, hypolipidemic, antihyperten-

M. Mahmoodi et al. / Advances in Biological Chemistry, 2011, 1, 29-33 30
sive, antidiabetic, antithrombotic and antihyperhomo-
cysteinemia effects [8]. These vegetables also have an-
timicrobial, antioxidant, anticarcinogenic, antimutagenic,
antiasthmatic and immuno-modulatory activities [9,10]
Some studies confirmed anti-hyperglycemic [11] effects
of garlic. The hypoglycemic potency of garlic has been
attributed mainly to allicin and its derived sulphur com-
pounds [12]. Amelioration of atherosclerosis by garlic
(Allium sativum) was also evidenced in both human
[13,14] and experimental animal models [15]. We have
previously shown that consumption of raw garlic had
hypolipidemic and hypoglycemic effects [16].
Other study suggested that garlic supplementation
significantly reduced serum glucose but increased serum
insulin and liver glycogen [17]. Investigations suggested
that garlic reduces lipid synthesis and influenced glyco-
gen metabolism in the liver of rats [17]. The hypoglyce-
mic effect of garlic seems to be associated with the ele-
vation of insulin level. The increased insulin response
also promotes the conversion of the inactive form of
glycogen synthetase to the active and enhances conver-
sion of blood glucose into glycogen [17]. Therefore, it is
clear that hormones are one of the most effective factors
in reduction of blood lipid and sugar. Furthermore, be-
cause to date, hormonal surveys have reported only on
animal experiments, thus, we designed the current study
to measure factors such as FBS, cholesterol, TG, HDL-C
and LDL-C, thyroids hormones (T3, T4, TSH) and insu-
lin in hyperglycemic and/or hyperlipidemic individuals
to find out the possible pathways that garlic may control
on sugar and lipid metabolism.
2. MATERIALS AND METHODS
In this clinical survey, 85 volunteers that have been in-
formed of the aim of the experiment of method divided
in to three groups following enter to the study.
Group 1: Volunteers with FBS (fasting blood sugar)
more than 126 mg/dl (30 people, 17 female and 13 male,
mean ages 45.2 ± 9.2).
Group 2: Volunteers with cholesterol higher than 245
mg/dl (30 people, 19 female and 11 male, mean ages 42
± 6.1).
Group 3: This group included volunteers with BS
more than 126 mg/dl and cholesterol higher than 245
mg/dl (25 people, 17 female and 8 male, mean ages 46.2
± 7.4).
All groups had normal diet and weren’t using any
sugar or lipid reducer drugs and also were matched for
age and body mass index (BMI). All of volunteers take
part in the study with completely satisfaction and aware-
ness. Initially, fasting blood samples were collected and
biochemical and hormonal factors were measured. Gar-
lic units were supplied, and were used for 42 days (10
gr/day, in 2 meals) by volunteers and the study was fol-
lowed by second blood samples collection and assess-
ment of the biochemical factors. Afterward, volunteers
didn’t take garlic for 6 weeks and then the third fasting
blood samples were collected and biochemical factors
were measured. Measured biochemical factors were:
FBS, total cholesterol, HDL-C, LDL-C and TG that as-
sayed by BT-3000 auto-analyzer apparatus and glycated
hemoglobin was measured by chromatography. The level
of thyroids hormones T3, T4 and TSH and insulin were
quantified by gamma-counter machine using RIA or
IRMA method. Data were analyzed by SPSS software
version 13 and where P value was less than 0.05, the
differences was considered as significant.
3. RESULTS AND DISCUSSION
In the first group (30 volunteers with FBS more than 126
mg/dl) the averages of the measured factors in three
steps were compared and didn’t show any significant
differences (Table 1).
In the second group (30 volunteers with blood choles-
terol over 245 mg/dl), following 42 days garlic con-
sumption had significant decrease in the level of FBS (P
< 0.01), total cholesterol (P < 0.001) and TG (P < 0.01)
and after 42 days of stopping garlic consumption as a
part of daily diet FBS and TG elevated while HDL-C
average decreased. Other measured biochemical factors
and hormones shown no significant differences (Table
2). The third group (25 volunteers with FBS more than
126 mg/dl and blood cholesterol higher than 245 mg/dl),
following 42 days using garlic the level of FBS (P <
0.01) and also total cholesterol (P < 0.001) were signifi-
cantly decreased. Glycated hemoglobin significantly de-
creased (P < 0.01) as well as FBS (P < 0.01). The HDL-C
level significantly increased after 42 days garlic consump-
tion (Ta b le 3 ). In this group similarly as other group we
couldn’t find any significant changes in hormones level.
In this study, following 42 days garlic consumption
(10 grams daily), blood cholesterol decreased in the
second and third group which was statistically signifi-
cant (P < 0.001), but there isn’t any significant differ-
ences in biochemical factors in first groups that we can
conclude garlic has more effect on lipid profile than glu-
cose as previous studies demonstrated too [6,13,15,16].
These findings were consistent with Kannar et al, results
that showed using garlic for 12 weeks decreased total
cholesterol and LDL-C about 4.2% and 6.6% respec-
tively [18]. In our study after garlic consumption, HDL-C
was increased significantly while LDL-C and TG didn’t
show a significant change. Morcos NC reported that con-
sumption of fish oil and garlic decreased serum choles-
terol and TG about 11% and 34%, respectively [19].
Some other studies evidenced that garlic didn’t have any

M. Mahmoodi et al. / Advances in Biological Chemistry, 2011, 1, 29-33 31
Table 1. Comparison of measured biochemical factors & hormones in 3 steps of study in group with FBS more than 126 mg/dl (n =
30, F = 17, M = 13, mean age = 45.2 ± 9.2).
Blood Factor Step 1
mean ± SEM Step 2 mean ± SEM Step 3 mean ± SEM
FBS (Mg/dl) 174.17 ± 6.9 164.4 ± 7.3 175.5 ± 8.1
Glycated Hemoglobin (%) 8.3 ± 0.18 7.9 ± 0.21 8.1 ± 0.17
Insulin (μIU/ml) 10.47 ± 3.8 9.28 ± 3.1 9.1 ± 3.5
TSH (ng/ml) 1.8 ± 0.56 1.8 ± 0.6 1.87 ± 0.7
T3 (ng/ml) 1.9 ± 0.53 1.9 ± 0.45 1.7 ± 0.32
T4 (ng/ml) 118 ± 54.6 111 ± 43.6 110 ± 43.2
Total cholesterol (Mg/dl) 207.8 ± 5.01 195.3 ± 4.5 207.03 ± 5.9
HDL-C (Mg/dl) 42.5 ± 0.9 44.4 ± 1.01 43.1 ± 0.8
LDL-C (Mg/dl) 99.5 ± 2.5 100.2 ± 2.3 104 ± 2.5
TG (Mg/dl) 154.3 ± 10.7 145.3 ± 08.2 156 ± 9.6
Step 1: at the beginning of study;
Step 2: 42 days after garlic consumption;
Step 3: 42 days after stopping of garlic consumption.
Table 2. Comparison of measured biochemical factors & hormones in 3 steps of study in group with blood cholesterol more
than 245 mg/dl (n = 30, F = 19, M = 11, mean age = 42 ± 6.1).
Blood Factor Step 1
mean ± SEM Step 2 mean ± SEM Step 3 mean ± SEM
FBS (Mg/dl) 99.6 ± 2.02 92.9 ± 2.2 a** 98.5 ± 2.4 b*
Glycated Hemoglobin (%) 5.64 ± 0.14 5.67 ± 0.09 5.76 ± 0.09
Insulin (μIU/ml) 6.7 ± 2.18 6.9 ± .2 6.5 ± 1.6
TSH (ng/ml) 1.93 ± 1.2 1.8 ± 1 1.96 ± 0.8
T3 (ng/ml) 1.95 ± 0.48 1.86 ± 0.32 1.85 ± 0.43
T4 (ng/ml) 126.5 ± 26 117 ± 24 117 ± 32
Total cholesterol (Mg/dl) 278.5 ± 4.7 248.4 ± 50.2 a*** 256.9 ± 5.8 b***
HDL-C (Mg/dl) 44 ± 1.2 48.1 ± 1.3 a*** 43.4 ± 0.8
LDL-C (Mg/dl) 103.6 ± 3.03 101.1 ± 2.35 106.9 ± 2.2
TG (Mg/dl) 227.1 ± 19.5 189.4 ± 16.2 a** 212.1 ± 16.2 b*
Step 1: at the beginning of study;
Step 2: 42 days after garlic consumption;
Step 3: 42 days after stopping of garlic consumption;
a: Signification differences in the second step compare to the first step;
b: Signification differences in the third step compare to the second step;
*: P < 0.05; **: P < 0.01; ***: P < 0.001.
Table 3. Comparison of measured biochemical factors & hormones in 3 steps of study in group with FBS more than 126 mg/dl and
blood cholesterol more than 245 mg/dl (n = 25, F = 17 , M = 8 , mean age = 46.2 ± 7.4).
Blood Factor Step 1
mean ± SEM Step 2 mean ± SEM Step 3 mean ± SEM
FBS (Mg/dl) 181.4 ± 12.5 163.3 ± 10.5 a** 98.5 ± 11.6
Glycated Hemoglobin (%) 8.1 ± 0.37 7.8 ± 34 a* 7.7 ± 0.3
Insulin (μIU/ml) 8.9 ± 6.3 8.7 ± 5 6.8 ± 3.6
TSH (ng/ml) 2.47 ± 0.36 2.47 ± 1.49 2.8 ± 0.9
T3 (ng/ml) 2 ± 0.8 1.9 ± 0.7 2 ± 0.62
T4 (ng/ml) 92 ± 31.2 84 ± 27.4 98 ± 25.5
Total cholesterol (Mg/dl) 272.08 ± 6.3 251.52 ± 6.3 a*** 260.52 ± 6.7
HDL-C (Mg/dl) 42.5 ± 0.9 43,6 ± 1.8 a* 44.6 ± 0.8
LDL-C (Mg/dl) 126.08 ± 5.5 122.7 ± 4.8 127.5 ± 4.5
TG (Mg/dl) 211.8 ± 16.7 220 ± 21.6 195.6 ± 12.7
Step 1: at the beginning of study;
Step 2: 42 days after garlic consumption;
Step 3: 42 days after stopping of garlic consumption;
a: Signification differences in the second step compare to the first step;
*: P < 0.05; **: P < 0.01; ***: P < 0.001.

M. Mahmoodi et al. / Advances in Biological Chemistry, 2011, 1, 29-33 32
significant impression on serum TG [20]. Beside of this
hypolipidemic effect of garlic, in present study, we ob-
served significant reduction of FBS and HbA1C in the
second and third groups (P < 0.01), that is in consistence
with Ahmed and Sharma who reported that using of gar-
lic oil decreases FBS in rats [21]. We didn’t observe any
significant changes in the level of T3, T4 and TSH hor-
mones during the three steps of our study. No relation
found between thyroid hormones and blood lipid in other
similar studies [22].
We didn’t find a relative previous study about the ef-
fect of garlic consumption on thyroid hormones in data-
base to compare with our study.
In this study we assessed the hormonal effect of garlic
because previous studies showed some of these effects.
The study have suggested that garlic supplementation
enhances protein anabolism and suppresses protein ca-
tabolism (due to hormonal regulation by the stimulation
of steroid hormones), thus, leading to greater testis tes-
tosterone content and lower plasma corticosterone con-
centration in rats treated with a high protein diet [23].
Further to thyroid hormones we measured the insulin
levels in the study and didn’t observe any significant
change.
Insulin plays a key role in the metabolism of lipids
apart from its regulatory effects on carbohydrate me-
tabolism.
Many studies imply the antioxidant and insulinoid ef-
fects of some trace elements like selenium, germanium
and vitamin C which all found in garlic [24].
Clinically probably, we can conclude that using garlic
in long term causes decreased cholesterol and FBS level
possibly by distinct hormonal mechanisms, as it was
proved in many investigations similar to the present
study but we didn’t observe any change in hormones’
level. According to the slightly side effects of garlic, it
can possibly be used as an auxiliary medicine for hyper-
cholesterolemic and hyperglysemic treatment.
It was shown that consumption of fruit and vegetables
prevents some diseases [4]. Garlic has been recognized
since ancient times not only as a flavoring agent for food
but also for its medicinal properties, including bacteri-
cidal, antineoplastic, hypolipidemic, hypocholesterolemic
and hypoglycemic effects [25].
In conclusion as reflected by other studies our results
shown that raw garlic consumption can reduce the FBS
and Lipid in hyperglycemic and/or hyperlipidemic indi-
viduals but in the period of this study we had not found
any significant changes in measured hormones. In future
we think if another study with longer duration would be
carried out on the effects of garlic on hormones a differ-
ences may be observed.
These results are in consistent with several clinical
reports, including meta-analyses, that have revealed hy-
poglycemic and hypolipidemic effects of garlic supple-
mentation in humans. Consequently, authors of this arti-
cle suggest that garlic may be prescribed in 10 - 20 gr
daily dosage as a supportative treatment in with little
side effects for diabetic and hyperlipidemic patients.
4. ACKNOWLEDGEMENTS
The reported work was supported by Rafsanjan University of Medical
Sciences.
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