Clinical Briefs
Clinical Briefs
With Comments from John La Puma, MD, FACP
Garlic for Hypercholesterolemia
January 2001; Volume 4; 11
Source: Stevinson C, et al. Garlic for treating hypercholesterolemia. A meta-analysis of randomized clinical trials. Ann Intern Med 2000;133:420-429.
We investigated the effect of garlic on total cholesterol level in persons with elevated levels by conducting a meta-analysis of randomized, double-blind, placebo-controlled trials. We conducted systematic literature searches on the MEDLINE, EMBASE, BIOSIS, Cochrane Library, AMED, and CISCOM databases. In addition, manufacturers of commercial garlic preparations and experts in the field were asked about published or unpublished trials. Selected trials were required to state that they were randomized, double-blind, and placebo-controlled; to use garlic monopreparations; to include persons with mean total cholesterol levels of at least 5.17 mmol/L (200 mg/dL); and to report total cholesterol level as an endpoint. There were no language restrictions. Two reviewers, blinded to key identifiers of each paper, independently extracted data in a standardized manner and assessed methodologic quality by using the Jadad scale. Discrepancies were settled through discussion.
In the 13 trials included in the meta-analysis, garlic reduced total cholesterol levels from baseline significantly more than placebo (P < 0.01); the weighted mean difference was -0.41 mmol/L (95% confidence interval [CI], -0.66 to -0.15 mmol/L) (-15.7 mg/dL [CI, -25.6 to -5.7 mg/dL]). Six diet-controlled trials with the highest scores for methodologic quality revealed a nonsignificant difference between garlic and placebo groups; the weighted mean difference was -0.11 mmol/L (CI, -0.30 to 0.08 mmol/L) (-4.3 mg/dL [CI, -11.7 to 3.1 mg/dL]).
The available data suggest that garlic is superior to placebo in reducing total cholesterol levels. However, the size of the effect is modest, and the robustness of the effect is debatable. The use of garlic for hypercholesterolemia is, therefore, of questionable value.
COMMENT
In American folklore, garlic was put into old socks and worn around the neck to cure colds and to ward off evil spirits, Dietz reports (see Alternative Medicine Alert, March 1999, pp. 28-31). In his authoritative 1998 review of garlic for cholesterol, Sorrentino noted, "Studies in isolated hepatocytes indicate that key enzymes in cholesterol biosynthesis, including HMG-CoA reductase, may be inhibited by the sulfur-containing substances in garlic....I recommend the use of fresh garlic as a component of a plant-centered diet and as part of an overall strategy of lifestyle modification to lower cholesterol levels. The equivalent of one clove per day is sufficient." (See Alternative Medicine Alert, September 1998, pp. 97-99.)
This pragmatic advice still seems sound, more than two years later. Does the present state-of-the-art meta-analysis tell us any different? In a word, no, and it is not high on tablets and powders. These Exeter investigators tested garlic supplements against evidence-based medicine’s best statistical standard. Trials through November 1998 were reviewed, and only 13 of 39 passed meta-analysis muster, with 796 patients total.
Garlic supplements and preparations, not surprisingly, are inefficient for lowering cholesterol. These authors estimate a 4-6% reduction on total cholesterol level (using essential oil, spray-dried powder, or the standardized powder Kwai®, for eight weeks to 10 months, in their pooled data). Another meta-analysis published several years ago in the same journal found a 9% reduction. LDL was not significantly reduced, nor HDL significantly increased in those trials that reported these data. Placebo reduced cholesterol about 0.6%.
Contrast this with statins, with 17-32% reductions, and the truly motivated, genetically amenable individual: One of my own patients went from 302 mg/dL to 146 mg/dL in six months by losing 20 pounds, increasing fiber, fish, and soy protein, decreasing saturated and trans fats, and training for a 5k.
Recommendation
Suggest heads and cloves of real garlic to your patients looking for flavor, and serious lifestyle measures to those looking for cholesterol-changing results. Prepared garlic supplements will help a little, but the money required might be better spent at a farmer’s market.
January 2001; Volume 4; 11
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