Garlic: Effects on Cardiovascular Risks and Disease, Protective Effects Against Cancer, and Clinical Adverse Effects

There are insufficient data to draw conclusions regarding garlic's effects on clinical cardiovascular outcomes such as claudication and myocardial infarction. Garlic preparations may have small, positive, short-term effects on lipids; whether effects are sustainable beyond 3 months is unclear. Consistent reductions in blood pressure with garlic were not found, and no effects on glucose or insulin sensitivity were found. Some promising effects on antithrombotic activity were reported, but few data are available for definitive conclusion.

Using "any" garlic supplement for less than 3 to 5 years was not associated with decreased risks of breast, lung, gastric, colon, or rectal cancer. Some case-control studies suggest that high dietary garlic consumption may be associated with decreased risks of laryngeal, gastric, colorectal, and endometrial cancers, and adenomatous colorectal polyps.

Multiple adverse effects, including smelly breath and body odor, dermatitis, bleeding, abdominal symptoms, and flatulence, have been reported. Whether adverse effects occur more commonly with certain preparations than others was not established. Furthermore, the causality of the adverse effects was not clear, except for breath and body odor, and the expected frequency of adverse effects was not determined.

Garlic: Effects on Cardiovascular Risks and Disease, Protective Effects Against Cancer, and Clinical Adverse Effects. Summary, Evidence Report/Technology Assessment: Number 20. AHRQ Publication No. 01-E022, October 2000. Agency for Healthcare Research and Quality, Rockville, MD. http://www.ahrq.gov/clinic/epcsums/garlicsum.htm