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FILE: §Complementary and Alternative Medicine §Herbal Medicine §Systematic Review §Clinical Studies HC 091224 -225 Date: January 30, 2003 RE: Annotated Bibliography of Complementary Therapy Reviews Linde K, ter Riet G, Hondras M, Vickers A, Saller R, Melchart D. Systematic reviews of complementary therapies—an annotated bibliography. Part 2: Herbal medicine. BMC Complementary and Alternative Medicine 2001; http://www.biomedcentral.com/1472-6882/1/5. Complementary and alternative medicine (CAM) is now widely used but remains controversial. The authors have conducted comprehensive literature searches about three major areas of CAM: acupuncture, homeopathy, and herbal medicine. This article describes the authors' systematic review of herbal medicine. The findings are presented as an annotated bibliography with a discussion. A total of 58 review articles met the inclusion criteria. These criteria were that the articles had to review prospective clinical trials, describe review methods explicitly, focus on treatment effects, and be published. The studies did not need to be controlled, but had to be about human subjects. Thirty of the reviews were of either ginkgo (Ginkgo biloba), St. John's wort (Hypericum perforatum), or garlic (Allium sativum). The remaining 28 reviews were of other herbal medicines. Overall, the authors found that "the quality of primary studies was criticized in the majority of the reviews. Most reviews judged the available evidence as promising, but definitive conclusions were rarely possible." In addition, the authors' search showed that "systematic reviews are available on a broad range of herbal preparations prescribed for defined conditions." For each herb, the authors summarize the findings reported in the review articles that they selected. They present their summary as a 6-page annotated bibliography with a discussion in the text. Thirteen review articles discussed ginkgo, which was studied for its effects on intermittent claudication (calf pain during walking), dementia, tinnitus (ringing in the ears), and macular degeneration (an eye disease causing loss of central vision). Seven articles were of intermittent claudication, and most of these found that ginkgo extracts were more effective than placebo for improving the patients' ability to walk comfortably; however, some reviewers concluded that the
clinical relevance of these effects was only moderate. The five reviews of ginkgo for dementia and cerebral insufficiency all reached positive conclusions, but many of the studies included patients with minor cognitive impairment. Evidence of ginkgo's effectiveness in more severe dementia was lacking. One review reported that ginkgo may be effective in relieving tinnitus, while another reported that there was insufficient evidence of effectiveness in macular degeneration. Nine review articles discussed St. John's wort as a treatment for depression. The reviews reached similar conclusions, reporting that St. John's wort appears to be equivalent to other antidepressants and superior to placebo for treating mild to moderate depression. The herb also has fewer side effects than other antidepressants, but its long-term safety and effectiveness still need to be established. Eight review articles discussed garlic for reducing cardiovascular risk factors and atherosclerosis. "A modest short-term effect over placebo on lipid-lowering seems to be established, but the clinical relevance of these effects is uncertain," the authors report. Also, the effects of garlic on blood pressure appear to be minor, and its influence on platelet aggregation and fibrinolytic activity seem promising but preliminary, the authors say. Research on garlic is difficult to interpret because many different garlic preparations have been used, and they generally do not contain the same amounts of bioactive ingredients. The authors conclude that their review must be interpreted with caution. "What we performed is a systematic review of systematic reviews, which inherently bears a large risk of oversimplification," they note. Readers who wish to evaluate the research evidence about a specific herb for a certain condition should read the individual review articles rather than relying on the present article, the authors say. The goal of the present article was to facilitate access to the relevant reviews and give readers a sense of the quantity of data available. In addition, the authors comment that systematic reviews regarding the traditional uses of many herbs in Third World countries are usually not available. Instead, the available studies focus on herbal products marketed and used in developed countries. Many traditional healers combine herbs and individualize these combinations for each patient. These practices will most likely remain under-researched because of methodological difficulties and a lack of financial incentive for demonstrating the effectiveness of such practices. Finally, the authors caution readers that herbal medicines can cause serious side effects and can interact with other herbs and drugs, even though herbal medicines are generally considered to be reasonably safe. —Christina Chase, MS, RD
Enclosure: Referenced article reprinted with permission from BioMed Central.
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