Effect of Dried Garlic Supplementation on Blood Lipids in Mild and Moderate Hypercholesterolemic Patients
M. Rahmani MD,* A. Khaleghnejad Tabari MD,* M.R. Khsosi Niaki MD,**
S. Allahaverdian MD,* M. Sheikholeslami MSc*
*Lipid Research Clinic, and **Department of Cardiology, Shahid Beheshti Hospital, Babol University of Medical Sciences, Babol, Iran
Background-Garlic has been reported to reduce cholesterol and other serum lipids. The beneficial effects of garlic powder supplementation is however, a matter of controversy.
Objective-To investigate the lipid-lowering effect of dried garlic supplimentation in hypercholestrolemic patients.
Methods-The effects of dried garlic powder tablets (Garlet7) on the serum lipid and lipoprotein levels were studied in 93 primary hypercholesterolemic subjects over a period of 12 weeks. In a placebo-controlled, randomized, double-blind parallel trial, patients were randomized into four groups and were given 1200, 2400, and 3600 mg/day of Garlet. Serum lipid and lipoprotein levels were measured at the beginning and at the end of the study. No dietary intervention was implemented during the trial. A two-day diet recall with Food Frequency Questionnaire (FFQ) was obtained at the baseline and at the end of the study. No significant changes were demonstrated in nutrient components and calorie intake between and within each group during the trial.
Results-The serum cholesterol and LDL-cholesterol in the treatment group, who received 2400 mg/d of Garlet, was reduced by 21.2 mg/dL (8.2%, p<0.001), and 20.4 mg/dL (11.7%, p<0.002), respectively, during the 12-week study period. The serum triglyceride in the those who received 1200 mg/d, decreased by 28.1 mg/dL (11.8%, p<0.009), by the end of the trial. Serum HDL-cholesterol was not altered significantly.
Conclusion-Garlic powder supplementation has some beneficial effects on the known atherosclerotic risk factors including serum cholesterol, triglyceride and LDL-cholesterol. Furthermore, it was found that the efficacy of garlic was not linearly dose dependent.
It is widely held that the major precipitating factors in coronary artery disease (CAD) are usually hypercholesterolemia, especially elevated LDL-cholesterol, oxidation of LDL, hypertension, decreased fibrinolytic activity, increased serum fibrinogen level, and enhanced platelet aggregation. It has been reported that garlic lowers plasma cholesterol and triglyceride levels,1-3 decreases fibrinogen levels,4 and increases the fibrinolytic activity in both human and experimental animals.4,5 ADP-induced platelet aggregation inhibition has been described since 1978,6-8 both in vitro and ex vivo. These results have later been confirmed by other authors.9-12 A recent report suggests that garlic powder extracts also acts as an antioxidants both in vitro13 and in vivo.14 In contrast, some studies failed to show any beneficial effect of dried garlic powder on blood lipids, fibrinolysis, coagulation,3 and platelet aggregation.15,16 Therefore, we conducted a trial on human subjects to reevaluate the effects of garlic on plasma lipid profile of hypercholesterolemic patients.
Subjects and Methods
One hundred and eight male and female patients who referred to the Lipid Clinic of Babol University of Medical Sciences (LBUMS) and had primary hypercholesterolemia (cholesterol > 220 mg/dL) and fasting serum triglycerides < 400 mg/dL, were enrolled into this study. Subjects ranged from 30-70 years of age, with body mass index of less than 35 kg/m2. Individuals treated with lipid lowering drugs, corticosteroids, hormones, diuretics, anticoagulants, fish oil or those who received garlic preparations during three months prior to the study, were excluded from the trial. Pregnant women, diabetic individuals and those with clinically significant renal, hepatic, pulmonary, hematologic, thyroid, cardiovascular, or active gastrointestinal disease, were also excluded from the study. Also patients with a positive history of sensitivity to garlic were not included in the trial. All subjects gave informed written consent.
In a randomized, double-blind placebo-controlled, parallel clinical trial, subjects were followed for 12 weeks. After one week, during which subjects were evaluated for inclusion and exclusion criteria, they where randomly assigned to receive placebo or garlic tablets (Garlet7, 400 mg dried garlic powder, Kowsar Pharmaceutical Co., Iran). Patients in group A received a placebo, and those in groups B, C and D received 1200, 2400, and 3600 mg/day of Garlet, respectively, for 12 weeks.
Subjects were requested not to alter their smoking, exercise and dietary habits during the course of the study. Patients meeting the inclusion criteria after the second visit during the baseline period were randomized into four study groups by the secretary of the clinic.
Informed consent, a medical history, a physical examination, baseline laboratory measurements (urinalysis, liver and renal function tests, hematologic indices, a full chemistry panel) and a two-day diet recall with Food Frequency Questionnaire (FFQ), were obtained for each subject during the first week. The patients were followed at 2, 4, 6, 8, 10 and 12 weeks of the study. Tablets were given to patients on all but the last visits. Unused tablets were returned and counted for measuring the compliance on all but the first visits. At six and twelve weeks from the beginning of intervention, body weight, diet recall and FFQ were obtained and total serum cholesterol,18 triglycerides,19 HDL-cholesterol20 concentrations. FFQ was taken to determine whether the changes in plasma lipid levels, if any, were due to garlic or to a change in diet. Serum LDL-cholesterol concentrations was calculated as described by Friedewald, et al.21
Data were analyzed by SPSS software. One way ANOVA, and Duncan's multiple range tests were used when applicable. Paired t-test was implemented for within group comparison.
Ninety-three participants completed the trial. No significant difference was observed among groups regarding age, body weight, and BMI at baseline.
Tables 1 and 2, demonstrate the lipid profile and ratios at baseline and after 12 weeks in the study groups. Baseline triglycerides in group B differed from that of groups C and D (Table 1 and 2).
In none of the groups, during the study period, drug compliance was less than 90%. In group C, cholesterol levels decreased significantly (p<0.001) from 259.3 mg/dl, at the baseline, to 238.1 mg/dl, after 12 weeks. The cholesterol level of patients in group C was different from both groups A and B, at the 12th week of the study (p<0.05).
Garlic supplementation in group B reduced triglycerides level from 238.2 mg/dl at baseline to 210.1 mg/dl (p<0.01) at the 12th week. LDL-cholesterol was altered significantly (p<0.002) in group C, from 172.2 mg/dl to 153.8 mg/dl during the study period. Also, mean difference of LDL-cholesterol levels for group C was different from group B (p<0.05) at the end of the trial (Table 1). Garlic supplementation in different dosages and placebo did not alter serum HDL-cholesterol during the 12 week trial (Table 1, 2).
In the present study, garlic supplementation demonstrated beneficial effects on the serum total cholesterol, LDL-cholesterol and triglycerides. Reports from medical literature have suggested that oral garlic supplementation may be effective in reducing serum cholesterol levels by as much as 15-20%.24 In five studies similar to our trial, the beneficial effects of standard garlic powder tablets on decreasing serum cholesterol were shown.7,25-28 In these trials dosages of dried garlic altered from 600 to 1000 mg/d and the lowest duration of intervention was eight weeks.
In the current study, garlic supplementation with dosages of 2400 mg/d (group C) reduced serum cholesterol level by as much as 21.2 mg/dl (8.2%, p<0.001). In the trials mentioned above,7,25-28 the beneficial dosages of garlic were determined to be less than 1000 mg/d, while a background dietary intervention was also implemented. In our study, however, no dietary intervention during the trial was implemented and no significant diet component alterations were detected with regards to calorie, nutrients, and fiber intake over the 12 week period.
Previous reports showed that dried garlic had beneficial effects with regards to triglycerides.29,30 On the other hand, one major meta-analysis that enrolled 925 subjects from 16 trials estimated a net triglyceride decrease attributable to garlic of 12 mg/dl (95% CI: 5.5 to 19).30 In that meta-analysis the range of dried garlic dosages in different trials was 600-900 mg/d.
In the present study, the average serum triglyceride levels were not homogenous in the four study groups. Therefore, garlic supplementation decreased triglyceride levels in group B (1200 mg/d) by as much as 28.1 mg/dl (11.8%, p<0.01) (Table 1). Because of a low average level of serum triglyceride in groups C and D, that is, about 200 mg/dl at baseline, the efficacy of garlic supplementation on lowering serum triglyceride can not be evaluated properly in these groups.
Some reports showed the beneficial effects of dried garlic powder on serum LDL-cholesterol.29,31 In our study, garlic preparation with dosages of 2400 mg/d reduced LDL-cholesterol by as much as 20.4 mg/dl (11.7%, p<0.002) (Table 1). Recent reports demonstrated that garlic powder preparations reduce lipoprotein oxidation susceptibility in vitro13 and in vivo.14 These results support the hypothesis that garlic has a beneficial effect on the atherosclerotic processes, even if the beneficial effect of garlic on serum LDL level is not mentioned.
Recent data from clinical trials, have shown increasing effects of dried garlic on serum HDL-cholesterol level.29,32 However, our trial did not demonstrate any significant changes on serum HDL-cholesterol level. TC/HDL-C and LDL-C/HDL-C ratios had no significant improvement during the intervention period.
In the present study, we achieved the same results as in other similar trials showing the efficacy of garlic supplementation in lowering total cholesterol, LDL-cholesterol and triglyceride levels. However, the doses of dried garlic powder tablets that were used in this study, were higher than what administered earlier. In fact, by prescribing up to three times the doses administered previously and for longer periods, we attained less improvement in cholesterol. By lower doses, no beneficial effects were achieved. The reasons for this difference seems to be the lack of dietary intervention or possibly, the difference in biologically active substances in our supplementation that was utilized in the present trial. It is concluded that garlic displays some beneficiary effects but the results should be regarded cautiously and no improper exaggeration should be made.
We thank Sh. Rezai Majd, M.H. Nadimi, Sh. Keyhani for their help in conducting the study, M. Hatefi, N. Behrozi for providing the garlic preparation (Kowsar Pharma Co.), B. Sarkari for his assistance, and F. Handjani for his aid in editing the manuscript.
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