|LE Magazine January 2000|
Anti-Atherosclerotic Effects of GARLIC
Garlic protection against atherosclerosis and heart disease can be partly ascribed to some of its known multiple functions in reducing risk factors: lowering blood cholesterol and other lipids, anticoagulation effects and antioxidant actions. Subjects with moderately high blood cholesterol given aged garlic extract supplement, in a double blind crossover study (Am J Clin Nut 1996;64:866-870), showed after six months a decrease in total cholesterol and harmful LDL and a lowering of blood pressure, as compared to placebo.
Another study (Atherosclerosis 1999;144: 399-404) tested the effects of garlic in preventing oxidation of human LDL cholesterol. Oxidized LDL is a risk factor for plaque formation. LDL cholesterol taken from the blood of subjects who were supplemented with aged garlic extract, fresh garlic or placebo (no garlic) showed different responses to oxidation. After seven days of garlic intake, LDL particles of garlic users showed resistance to oxidation, compared to placebo. LDL from consumers of Kyolic aged garlic extract showed the highest degree of resistance to oxidation, indicating a higher antioxidant activity compared to fresh garlic.
Plaque in arteries present a risk factor for atherosclerosis and heart disease. They begin early in life by the development of fatty streaks in the smooth muscle of the arterial wall. Plaques formation increases with age and with exposure to high risk factors such as a high fat diet, high cholesterol, smoking and diabetes. Plaques in the common carotid artery double the risk of heart attacks and plaques in the femoral artery double the risk of heart disease due to insufficient blood supply.
Two studies have tested that ability of garlic supplementation to prevent and possibly reverse atherosclerotic plaques. A study on rabbits (Atherosclerosis 1997; 132: 37-42) investigated the effects of Kyolic aged garlic extract on the development of fatty streaks in arteries of rabbits fed high and low cholesterol diets. Fatty streaks are growths of fibrous fatty deposits in the smooth muscle tissue of the arteries and are markers of early atherosclerotic lesions. The study used four groups of animals. Group one received a standard diet, group two a standard diet plus odor free Kyolic, group three a standard diet supplemented with 1% cholesterol, and group four, a standard diet supplemented with 1% cholesterol plus Kyolic.
After six weeks rabbits of group three developed fatty streaks covering 70% of the surface area of the large artery studied (thoracic aorta), which was reduced to 2.5% in the Kyolic treated group four. No fatty streaks were present in groups one and two. The high cholesterol diet in group three caused cholesterol accumulation in the aorta, which was reduced by 50% in the Kyolic supplemented rabbits, in group four. Kyolic also prevented the in vitro growth of smooth muscle cells that occurs in plaque development. The effects were dose related. The higher the dose of Kyolic in the culture medium, the lesser the growth. The study also found that following injury of the carotid artery, Kyolic reduced fatty plaque formation in the intima of the carotid artery by 50%, compared to controls with high cholesterol diet and no Kyolic.
The authors of the study concluded that supplementing the diet with Kyolic aged garlic extract provides protection against the onset of atherosclerosis by reducing fatty streak development, lowering cholesterol accumulation in artery walls and preventing fatty plaques in the injured intima of arteries, in cholesterol fed animals.
Reduction in plaque development by garlic is further supported by another report (Atherosclerosis 1999;144:237-249). A double blind placebo controlled study tested the effects of 900 mg/day garlic powder, for 48 months, on plaque formation, using ultrasound examination to scan the carotid and femoral arteries. Criteria for participation in the study included the presence of atherosclerotic plaques and at least one of the established risk factors such as high blood pressure, high cholesterol, diabetes and smoking. Of the 280 patients that enrolled, 140 in the drug group (93 males and 47 females) and 140 in the placebo group (105 males and 33 females), 152 completed the 48 month treatment (62 in the garlic trial; 38 males and 23 females and 91 in the placebo group; 67 males and 24 females). The main reason for dropping out of the trial group (mostly younger females) was annoyance by the strong odor of the garlic powder. This resulted in the fact that younger women (ages 40-55) dominated in the placebo group and older women (over 55) in the garlic trial group.
The average plaque volume of all participants at the beginning of the study was 32.2 (+/- 2.3) mm2. After four years of garlic intake the calculated mean plaque volume of garlic users was 30.7 mm2 (+/- 1.6) as compared to the placebo 36.3 mm square (+/-2.4). In men the reduction in plaque volume as related to a four year effect was 12.5%. In women, where older women dominated the trial group, the increase in plaque volume with age was calculated to have decreased by 6.4% in relation to the 48 months of garlic intake. While age and gender were considered in the calculations, the response to garlic of subjects exposed to a particular risk factor was not considered possibly because of the small size of final participants in the study.
While larger clinical investigations are needed to add to the body of information, these studies show that continuous intake of garlic supplements can prevent the development of fatty streaks and atherosclerotic plaques and in some cases, may cause regression of the existing plaques.
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