Reviewed: Gardner CD, Lawson LD, Block E, et al. Effect of raw garlic vs. commercial garlic supplements on plasma lipid concentrations in adults, with moderate hypercholesterolemia; a randomized clinical trial. Arch Int Med. 2007;167:346-353.

Garlic (Allium sativum, Lilliaceae) is promoted to lower cholesterol and to have cardiovascular benefits. It is often packaged in more palatable forms so that the benefits of raw garlic can be obtained without the unpleasant gustatory and odoriferous effects. Nine trials published before 1995 reported that garlic tablets lowered cholesterol; in contrast, 20 clinical trials of garlic supplements since 1995 have shown no effect on cholesterol. The authors assumed that inconsistency was due to poor quality supplements or problems with design of the trials. In order to establish the truth on the cholesterol issue, the present study was conducted with (1) raw garlic, (2) the only brand of garlic powder supplement known to have similar allicin bioavailability as raw garlic (Garlicin®, Nature’s Way, Springville, UT), and (3) an aged formulation that has been evaluated in many clinical trials (Aged Garlic Extract®, aka Kyolic®, Wakunaga of America, Mission Viejo, CA).

Patients (n=192) with lower density lipoprotein (LDL) cholesterol levels ranging from 130-190 mg/dl participated in this placebo-controlled, 4-arm parallel group trial. Participants consumed 1 of 4 treatments: (1) placebo tablets, (2) 4.0 g blended raw garlic (an average-sized clove crushed in a blender), (3) 4 Garlicin tablets (twice the recommended dose), or (4) 6 Kyolic tablets (1½-3 times the recommended dose). The raw garlic dose had an allicin content similar to the allicin yield of the Garlicin dose, and both had a dry garlic matter content slightly less than the Kyolic dose. Individually packaged aliquots of raw garlic were frozen at ?80°C. When distributed, raw garlic aliquots were thawed, mixed with condiments, and served in sandwiches. The sandwiches were prepared by and distributed through the research center. All participants received the sandwiches, either with raw garlic or without, depending on the treatment group. Blinding of the raw garlic was not possible. However, investigators were blinded until all plasma lipid analyses were completed. The treatments were consumed 6 days per week for 6 months. Participants were instructed not to consume food with garlic and to minimize intake of raw onions and chives (Allium spp.). Blood samples were collected monthly.

Adherence to tablet and sandwich consumption was excellent. Approximately 55% of the participants correctly identified that they were receiving garlic supplements. There were no statistically significant differences by treatment group for any of the fasting plasma lipid concentrations over the course of the study. No serious adverse events occurred. Bad body and breath odor was reported as “often” or “almost always” by 57% of the raw garlic group, one participant in the Kyolic group, and no participants in the Garlicin or placebo groups.

The authors conclude that none of the garlic products had a statistically detectable or clinically relevant effect on plasma lipid concentrations in adults with moderate hypercholesterolemia. According to the authors, this study is the most scientifically rigorous clinical trial regarding serum cholesterol that has ever been conducted with garlic products.

Mark Blumenthal, founder and executive director of the American Botanical Council, commented to the San Francisco Chronicle in an interview after the trial was published that the “trial had a narrow research focus, i.e., LDL cholesterol, but that garlic’s potential and clinically documented cardiovascular benefits cover a wide range, and that it would be a mistake to dismiss garlic as a healthy addition to the diet simply based on the lack of documentation of LDL-cholesterol lowering effects.”¹ Blumenthal also mentioned that other research shows that garlic as a food and dietary supplement has some potential benefit in helping reduce the risk of certain types of cancers, particularly those of the gastrointestinal tract.

The bottom-line appears to be that while the trial provides significant evidence for the contention that fresh garlic and some leading commercial garlic dietary supplements do not have a clinically significant cholesterol-lowering effect, the study does not dismiss garlic’s potential utility in the prevention of cardiovascular disease. As pointed out by ABC’s Blumenthal in his “Dear Reader” column in HerbalGram 74, 6 clinical trials support the ability of garlic “to inhibit and even reverse the buildup of arterial plaque (atherosclero sis).”²

—Heather S. Oliff, PhD

References

1. Stanford University garlic trial published in Archives of Internal Medicine finds no cholesterol-lowering effect [member advisory]. Austin, TX: American Botanical Council; February 26, 2007.
2. Blumenthal M. Garlic trial shows no cholesterol-lowering effect; other cardiovascular benefits documented. HerbalGram. 2007;No. 74:6.