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Standardized Garlic Powder Reduces Heart Attack Risk

A study published in the May issue of Atherosclerosis showed that a garlic powder supplement (Allium sativum L., Liliaceae) can help prevent and, in some cases, even reverse plaque build-up in the arteries (Koscielny et al., 1999). Researchers have long associated arterial plaque with an increased risk of heart attack and stroke. The study was conducted using rigorous controls (randomized, double-blind, placebo-controlled) and took place over a four-year period, making it the longest clinical trial to evaluate the effects of a dietary supplement on reducing heart attack risk.

For the four-year study, 152 men and women were randomly assigned to take either placebo or 900 mg of standardized garlic powder daily (Kwai®, Lichtwer Pharma, Berlin). From the beginning, all participants had advanced plaque accumulation, in addition to at least one other established risk factor for heart disease, such as high cholesterol or blood pressure, diabetes, or a history of smoking. Researchers used B-mode ultrasound to measure the progression and regression of plaque volume in the common carotid and femoral arteries, at the beginning of the study and at 16, 36, and 48 months.

At the end of the study, those who took garlic had a 2.6 percent reduction in plaque volume, compared to a 15.6 percent increase in the placebo group. When the effects were analyzed by gender, there was a 4.4 percent decrease in plaque volume in men taking garlic, compared to a 5.5 percent increase in the male placebo group. The results for women initially took researchers by surprise. While women in the garlic group experienced a modest 4.6 percent decrease in plaque volume, those taking placebo had a massive 53.1 percent increase.

According to the researchers, the striking difference between the two female groups was due to a predominance of younger women in the placebo group, and more older women in the garlic group by the end of the study. Although the age distribution was relatively even at the beginning of the study, it became unbalanced as a greater number of younger women in the garlic group withdrew from the study, mostly due to "annoyance by odor." Unfortunately, this prevented the researchers from drawing meaningful conclusions about garlic based on the age composition of the study groups. Clearly, the double-blind design of the study was also defeated by the odor of the garlic pills, which were easily distinguished from the placebo pills. However, the investigators asserted that the 4.6 percent decline in plaque volume observed in women taking garlic remains a "genuine garlic effect."

Based on this study and more than 20 others conducted on standardized powdered garlic, researchers believe that garlic can have not only a preventative but also a curative role in heart disease. Previous studies demonstrate that powdered garlic reduces total and harmful LDL cholesterol levels, serum triglycerides, and blood pressure, and also inhibits cholesterol oxidation and platelet aggregation (the tendency of the blood platelets to clump), among other positive effects. This study adds more support to the scientific case for garlic as a "pleiotropic" substance, meaning that garlic's mild effects on many different measurements of heart health add up to significant overall benefits. - Krista Morien

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[Koscielny J, Klüssendorf D, Latza R, Schmitt R, Radtke H, Siegel G, Kiesewetter H. The antiatherosclerotic effect of Allium sativum. Atherosclerosis 1999; 144: 237-249.]

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