Garlic: a condiment for cholesterol control

Garlic’s benefits are not just folklore; one-half to one clove of garlic a day has been shown to decrease total cholesterol by about 9%.
By John Russo Jr.,

VICUS.COM (30 May 2000) — In certain Western European countries, people tend to consume a large amount of garlic, and these societies tend to have a lower incidence of coronary heart disease. Interestingly, these populations also eat large amounts of onions, which tend to confound the data.

Is it the garlic or the onions that reduce heart disease? This is a common problem when trying to determine causal relationships. It’s one thing to identify an association, but quite another to take the critical step of establishing a cause-and-effect relationship.

For example, legend has it that there is an association between Punxsutawney Phil seeing his shadow and six more weeks of wintry weather. But does anybody really believe there is a cause-and-effect relationship? (Hint: Statistically, Phil’s prognostications have been correct only 39% of the time.)

Garlic’s modest effect on cholesterol

The good news is that researchers have established a modest cause-and-effect relationship for the ability of garlic to lower blood cholesterol concentrations.

A meta-analysis of the controlled trials of garlic to reduce hypercholesterolemia shows a significant reduction in total cholesterol levels. Garlic, in an amount approximating one-half to one clove per day (600-900 mg), has been shown to decrease total serum cholesterol levels by about 9% (Warshafsky, et al., 1993). Other researchers have estimated the reduction at up to 12%.

People with a total blood cholesterol concentration of greater than 200 mg/dL may expect to achieve a reduction of about 23 mg/dL.

Mechanism of action

In the laboratory, garlic and wild garlic reduce serum cholesterol levels primarily by inhibiting cholesterol synthesis. Both have similar effects, which are related to the amount of garlic used and to a mixture of multiple compounds from the sulfur-containing class of thiosulfinates, ajoenes and dithiins.

Chloroform and acetone/chloroform extracts of garlic and wild garlic inhibit cholesterol synthesis 44% to 52%, while the five individual sulfur-containing compounds in garlic– ajoene, methylajoene, allicin, 2-vinyl-4H-1,3-dithiin and diallydisulfide — inhibit cholesterol synthesis by 37% to 72%.

Commercial garlic products

Whether these findings extend to commercially prepared garlic tablets or garlic oils remains to be proven. For example, total cholesterol; LDL cholesterol, HDL cholesterol and triglycerides were virtually unchanged in one study of a steam-distilled garlic oil preparation (5 mg twice daily) vs. placebo for 12 weeks.

Other parameters such as cholesterol absorption, cholesterol synthesis, mevalonic acid excretion and changes in the ratio of lathosterol to cholesterol in serum were also not different as a result of garlic vs. placebo treatment (Berthold  et al., 1998).


It is unclear whether the failure of one commercially prepared garlic preparation is indicative of all preparations or if the problem lies in an insufficient dosage.

For now, increasing dietary garlic provides one natural way to reduce cholesterol. For those worried about the aftertaste (and breath), consider that this socially unacceptable side effect of garlic can be minimized by slicing the garlic instead of smashing it in a press.

Healthful eating!

John Russo Jr., PharmD, is senior vice president of medical communications at He is a pharmacist and medical writer with more than 20 years of experience in medical education. 


Berthold HK, Sudhop T, von Bergmann K. Effect of a garlic oil preparation on serum lipoproteins and cholesterol metabolism: a randomized controlled trial. JAMA. 1998 Jun 17; 279(23):1900-2. Liu L, Yeh YY. Inhibition of cholesterol biosynthesis by organosulfur compounds derived from garlic. Lipids. 2000 Feb; 35(2):197-203.Pelletier, K. The Best Alternative Medicine. What Works? What Does Not? New York, (NY): Simon & Schuster; 2000.Sendl A, Schliack M, Löser R, Stanislaus F, Wagner H. Inhibition of cholesterol synthesis in vitro by extracts and isolated compounds prepared from garlic and wild garlic. Atherosclerosis. 1992 May; 94(1):79-85.

Warshafsky S, Kamer RS, Sivak SL. Effect of garlic on total serum cholesterol. A meta-analysis. Ann Intern Med. 1993 Oct 1; 119(7 Pt 1):599-605.