Stanford University Garlic Trial Published in Archives of Internal Medicine Finds No Cholesterol-Lowering Effect
Austin, Texas (February 26, 2007). Tomorrow the Archives of Internal Medicine will publish a clinical trial on patients with elevated cholesterol levels in which 3 different types of garlic (fresh plus 2 commercial brands) did not show any significant reduction in LDL cholesterol levels. 1 The randomized, double-blind, placebo controlled, 4-arm trial was conducted on 192 patients over a period of 6 months. The patients had LDL cholesterol levels ranging from 130-190 mg/dl.
The well-designed trial, conducted at Stanford University Medical School, included authors who are leading garlic experts, namely Eric Block, PhD of the University at Albany, State University of New York and Larry Lawson, PhD of Plant Bioactives Research Institute, a natural products testing lab in Utah. Dr. Block has previously published on the chemistry and pharmacology of plants in the genus Allium, including a major article in Scientific American, 2 and Dr. Lawson has co-authored a major book on garlic 3 and numerous scientific articles. About several years ago worked at Nature's Way, manufacturer of Garlicin®, one of the garlic supplements used in this trial.
In addition to fresh garlic and Garlicin, the other garlic product employed was Kyolic®, made by the Japanese company Wakunaga. Kyolic is the world's most scientifically and clinically researched garlic preparation.
Dr. Lawson told ABC that he and the other researchers were disappointed in the study's outcomes; they had hoped to show a positive effect. He also said that he believed that they had employed not only garlic preparations that the authors had deemed reliable based on previous research, but also that they were dosed at levels that the researchers deemed high enough to produce a beneficial reduction in cholesterol levels, i.e., ca. the equivalent of 4g fresh garlic bulb per day (the level approved by the German Commission E). This is the highest dose of raw garlic used in a placebo-controlled clinical trial and the dose of dried garlic powder supplements in a trial to measure a cholesterol effect. (Two previous trials on Kyolic Aged Garlic Extract used a higher dose than those used in the dried garlic powder trials.) Lawson said that many recent clinical trials on garlic have failed to show a cholesterol-lowering effect or showed only a modest effect.
In an email, Dr. Lawson wrote, “The results were very disappointing to both Gardner [the principal investigator] and myself. Although 9 trials published before 1995 with Kwai tablets reported that the tablets lowered cholesterol, about 20 clinical trials with garlic supplements since 1995 (including 5 with Kwai) have shown no effect on cholesterol. We assumed the inconsistency problem was due poor quality supplements (Kwai made a formulation change in their tablets in about 1994). Hence, the Stanford study was conducted with raw garlic as well as with the only brand of garlic powder supplement known to have similar allicin bioavailability as raw garlic, Garlicin, in order to finally establish the truth on the cholesterol issue. The Stanford study is the most scientifically rigorous clinical trial that has ever been conducted with garlic products on serum cholesterol. So, it really represents the truth for persons who don’t have extremely high cholesterol levels.”
He did, however, emphasize that clinical trials published since 1999 have shown an anti-atherosclerotic effect, a benefit of garlic that might warrant its continued use as a medicinal/functional food and as a dietary supplement. Referring to the new cholesterol study, he wrote, “These results do not mean that garlic…doesn’t have other cardiovascular benefits, such as on atherosclerosis, for which there are 6 small clinical trials that have shown consistently positive results, but need more thorough investigation. This point is made at the end of our paper.”
In an email, Haru Amagase, PhD, Director of Research and Development at Wakunaga, the makers of Kyolic Aged Garlic Extract®, wrote to the American Botanical Council with some of his views on this new trial:
“The effect of garlic and garlic supplements tends to work on high level of cholesterol but not so much on normal levels, based upon our observations in several clinical studies, which are not published yet.” He continued, “Garlic and garlic supplement, especially [Kyolic] Aged Garlic Extract works on the multiple risk factors of cardiovascular diseases including heart attack etc. These cardiovascular diseases are not caused by one single factor. [There are] many risk factors, such as blood pressure, platelet aggregation, poor circulation, endothelial dysfunctions, blood lipid level including cholesterol, triglycerides, and homocysteine level, obesity etc....Aged Garlic Extract is shown in many separate clinical studies that it reduces multiple risk factors in cardiovascular diseases.”
This new trial is receiving considerable media coverage. Within an hour and a half of the end of the embargo period today (3pm EST), over 70 articles on garlic and cholesterol were accessible on Google. The primary investigator, Christopher D. Gardner, PhD of Stanford University Medical School, has reportedly fielded calls for interviews from numerous media, including the Associated Press, CBS News, National Public Radio, the New York Times, among others.
Monday afternoon, ABC Founder and Executive Director Mark Blumenthal was interviewed by the San Francisco Chronicle about the trial. Blumenthal emphasized that this 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. Blumenthal also mentioned that research shows that garlic as a food and dietary supplements has shown some potential benefit in helping reduce the risk of certain types of cancers, particularly those of the gastrointestinal tract.
Last Friday Robert Borris, the new Vice President of Botanical Science at the Council for Responsible Nutrition, a dietary supplement industry trade association, was interviewed about this trial by the Associated Press and Bloomberg Business News. Among other things, he said that the primary use for garlic is not for treatment of high cholesterol but as a food and dietary supplement to promote general cardiovascular health.
An extensive review of garlic pharmacology and clinical trials is available in The ABC Clinical Guide to Herbs. 4
References
1. Gardner CD, Lawson LD, Block E, Chatterjee LM, Kiazand A, Balise RR, Kramer HC. 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.
2. Block E. The chemistry of garlic and onions. Sci Amer 1985;252(3):114-119.
3. Koch HP, Lawson LD (eds.). Garlic: The Science and Therapeutic Application of Allium sativum L. and Related Species, 2d. ed. Baltimore: Williams & Wilkins; 1996.
4. Garlic. In: Blumenthal M et al. (eds.) The ABC Clinical Guide to Herbs. Austin, TX: American Botanical Council; 2003.