Effects of Garlic Oil on Platelet Aggregation, Serum Lipids and Blood Pressure in Humans

The effect of oral ingestion of garlic oil was studied in 20 healthy human volunteers in a double-blind, two period, cross-over trial. The individuals were randomly divided into two groups. Each group rotated for four week periods through 2 different sequences of oral supplementation including: 18 mg of garlic oil (extracted from 9 grams of fresh garlic) and placebo. The amount of platelet aggregation decreased significantly (p< .005) during garlic administration. Serum cholesterol levels and mean blood pressure both decreased significantly (p<.011, p<.009) during garlic supplementation. Serum high density lipoprotein levels rose significantly (p.<.001) during garlic administration. There was a significant rise in arachidonic acid in red cell phospholipids following garlic administration. The results of this study (the first double-blind, crossover study) suggest that garlic has therapeutic potential as an anti-atherosclerotic, antithrombotic and antihypertensive agent in normal healthy adults. Garlic, known botanically as Allium sativum, is a widely distributed common plant. It is used in all parts of the world not only as a spice and food, but also as a popular folk remedy for a variety of ailments. Its importance had been recognized several thousand years ago in China, India 1. Supported in part by grant from General Nutrition Corporation. 2. Equipment donation by Chrono-Log Corporation. 3. Research Fellow, John Bastyr College of Naturopathic Medicine, 144 N.E. 54th St., Seattle, WA 98105. 4. Research Director, John Bastyr College. 5. Faculty, John Bastyr College. Correspondence and reprint requests to Dr. Stephen Barrie, Great Smokies Medical Center, Rt. 1, Box 7, Leicester, North Carolina, 28748. and Egypt. In 1944 the essential oil, believed to be the active ingredient, was distilled out and named Allicin . There recently has been renewed research in the therapeutic uses of garlic. Hypolipidemic, platelet aggregation inhibition", antiatherosclerotic" fibrinolytic enhancement, anti-bacterial and anti-fungal properties have all been reported. Atherosclerosis and coronary artery disease remain the number one killers in civilized countries of the world. It is now recognized that hyperlipidemia is associated with increased incidence of premature ischemic heart disease 8 . Hypercholesterolemia correlates highly with the risk of myocardial infarction. Elevated high density lipoprotein (HDL) levels may exert a protective effect against coronary artery disease. Due to the previously reported positive effect of garlic on these blood components in unblinded tests on animals and humans, this study was designed to test some of these parameters in a controlled double-blind study with normal human volunteers. Methods Twenty student volunteers, average 26 years of age, enrolled in the project. All completed informed consent letters and the project was approved by the Human Subjects Review Committee of the College. All were in good health and showed no signs of degenerative cardiovascular disease. Each person was given a list of drugs that affected platelet aggregation and was asked to avoid these during the trial. Individuals were also asked to limit dietary garlic. No other dietary restrictions were imposed. The design of the study was a double-blind, two-period crossover trial. The individuals were randomly divided into 2 groups.