AHRQ Report Finds Little or Inconclusive Evidence of Health Benefits of Garlic

Dietary use of garlic may lower some types of cholesterol in the short term, but it does not appear to offer long-term protection against cardiovascular disease, says a new evidence report released today by the Agency for Healthcare Research and Quality (AHRQ). Garlic may help to reduce low-density lipids (LDL), or “bad” cholesterol and triglycerides. However, the evidence is only for short-term (1 to 3 months) effects. The long-term benefits have not been determined. The levels of high-density lipids (HDL), or “good” cholesterol, were unaffected. After 6 months, no further reductions in either triglycerides or LDL were apparent. The report calls for additional research to examine the short-term benefits versus the long-term benefits of garlic consumption.

The authors found no evidence that garlic has a beneficial impact on blood pressure or diabetes. The evidence was inconclusive about garlic’s role in protecting against cancer. Dietary garlic may possibly be associated with decreased likelihood of some types of cancer, but the number of available studies was not sufficient to draw conclusions.

Another limitation of the current evidence is that research does not sufficiently address the variations in garlic preparations, such as raw, cooked or supplement form. Types of garlic and garlic preparations vary widely. As a supplement, it is available dehydrated in tablets and as extracts, oils, and in combination with other supplements.

The report, which was based on a systematic review and analysis of scientific evidence related to clinical studies of garlic in humans, was conducted for AHRQ by the San Antonio Evidence-based Practice Center at The University of Texas Health Science Center at San Antonio and the Veterans Evidence-based Research, Dissemination, and Implementation Center (VERDICT), a Veterans Affairs Health Services Research and Development Center of Excellence. It was requested by the National Center for Complementary and Alternative Medicine, a component of the National Institutes of Health. To arrange interviews with researchers at VERDICT, contact Jennifer Arterburn, at (210) 617-5300, ext. 4028.

The summary of Evidence Report Number 20, Garlic: Effects on Cardiovascular Risks and Disease, Protective Effects Against Cancer, and Clinical Adverse Effects, is available through AHRQ’s Web site at http://www.ahrq.gov/clinic/garlicsum.htm. Print copies are available from the AHRQ Publications Clearinghouse at P.O. Box 8547, Silver Spring, MD 20907-8547, or 800-358-9295 within the U.S. or (410) 381-3150 from outside the country. A copy of the full report will be available in winter 2000.

For more information, contact AHRQ Public Affairs (301) 594-1364: Jane Steele, (301) 594-6350 (JSteele@ahrq.gov).