Context.— Garlic-containing drugs have been used in the treatment of hypercholesterolemia
even though their efficacy is not generally established. Little is known about
the mechanisms of action of the possible effects on cholesterol in humans.
Objective.— To estimate the hypocholesterolemic effect of garlic oil and to investigate
the possible mechanism of action.
Design.— Double-blind, randomized, placebo-controlled trial.
Setting.— Outpatient lipid clinic.
Patients.— We investigated 25 patients (mean age, 58 years) with moderate hypercholesterolemia.
Intervention.— Steam-distilled garlic oil preparation (5 mg twice a day) vs placebo
each for 12 weeks with wash-out periods of 4 weeks.
Main Outcome Measures.— Serum lipoprotein concentrations, cholesterol absorption, and cholesterol
synthesis.
Results.— Baseline lipoprotein profiles were (mean [SD]): total cholesterol, 7.53
(0.75) mmol/L (291 [29] mg/dL); low-density lipoprotein cholesterol (LDL-C),
5.35 (0.78) mmol/L (207 [30] mg/dL); high-density lipoprotein cholesterol
(HDL-C), 1.50 (0.41) mmol/L (58 [16] mg/dL); and triglycerides, 1.45 (0.73)
mmol/L (127 [64] mg/dL). Lipoprotein levels were virtually unchanged at the
end of both treatment periods (mean difference [95% confidence interval]):
total cholesterol, 0.085 (−0.201 to 0.372) mmol/L (3.3 [−7.8 to
14.4] mg/dL), P=.54; LDL-C, 0.001 (−0.242 to
0.245) mmol/L (0.04 [−9.4 to 9.5] mg/dL), P=.99;
HDL-C, 0.050 (−0.028 to 0.128) mmol/L (1.9 [−1.1 to 4.9] mg/dL), P=.20; triclycerides, 0.047 (−0.229 to 0.135) mmol/L
(4.2 [−20.3 to 12.0]) mg/dL, P=.60. Cholesterol
absorption (37.5% [10.5%] vs 38.3% [10.7%], P=.58),
cholesterol synthesis (12.7 [6.5] vs 13.4 [6.6] mg/kg of body weight per day, P=.64), mevalonic acid excretion (192 [66] vs 187 [66]
µg/d, P=.78), and changes in the ratio of lathosterol
to cholesterol in serum (4.4% [24.3%] vs 10.6% [21.1%], P=.62) were not different in garlic and placebo treatment.
Conclusions.— The commercial garlic oil preparation investigated had no influence
on serum lipoproteins, cholesterol absorption, or cholesterol synthesis. Garlic
therapy for treatment of hypercholesterolemia cannot be recommended on the
basis of this study.