Not a Clove of Difference? Garlic Insignificant vs. Cholesterol

STANFORD, Calif.A clove of garlic, either raw, powdered or as an aged garlic extract (AGE) form, had no statistically or clinically significant effects on bad cholesterol or other plasma lipid concentrations in adults with moderate hypercholesterolemia, according to a study out of Stanford University Medical School (Arch Intern Med, 167:346-353, 2007). The parallel-design trial consisted of 192 adults with low-density lipoprotein (LDL) cholesterol concentrations of 130 to 190 mg/dL (3.36-4.91 mmol/L). Each participant was given either raw garlic (4.0 g prepared in sandwiches), powdered garlic supplement (as four tablets of Garlicin®), AGE supplement (as six tablets of Kyolic®), or placebo. Garlic dosesequivalent to an average-sized garlic clovewere consumed six days per week for six months. Fasting plasma lipid concentrations were assessed monthly. Chemical characterization of study materials were continuously conducted, with high chemical stability of all garlic forms throughout the trial.

Retention was 87 to 90 percent in all four treatment arms, and chemical stability of garlic variations was high throughout the trial. There were no statistically significant effects of the three forms of garlic on LDL concentrations. At six months, the mean (SD) changes in LDL concentrations were +0.4 (19.3) mg/dL (+0.01 [0.50] mmol/L), for raw garlic; +3.2 (17.2) mg/dL (+0.08 [0.44] mmol/L), for powdered garlic; +0.2 (17.8) mg/dL (+0.005 [0.46] mmol/L), for the AGE supplement; and 3.9 (16.5) mg/dL (0.10 [0.43] mmol/L) for placebo. There were no statistically significant effects on high-density lipoprotein (HDL) cholesterol, triglyceride levels, or the total cholesterolHDL ratio. However, researchers noted garlic might lower LDL in specific subpopulations, such as those with higher LDL concentrations, or may have other beneficial health effects. Also, we studied only one dosage level, and effects might emerge at higher doses, if tolerated, they noted.

Steven Dentali, Ph.D., vice president of scientific and technical affairs at the American Herbal Products Association (AHPA), said: While the researchers did not find a cholesterol lowering effect from raw garlic and garlic preparations in this trial, they appropriately pointed out that garlic may confer cardiovascular benefits via other mechanisms. LDL cholesterol itself is not harmful until it oxidizes and forms plaque on arterial walls. This study measured only the effects on lowering LDL and not on its oxidation or on other risk factors for cardiovascular disease. This trial provides a reasonable indication to the question of Does garlic lower LDL cholesterol?, but offers no clinical information on how else it may support healthy cardiovascular function.

The study was supported by in part by grants from the National Institutes of Health (NIH).