Echinacea Does Not Prevent Colds, More Evidence Shows
The herbal supplement echinacea, when taken in certain forms, may help shorten the duration and severity of cold symptoms but is not effective for preventing the common cold, according to a systematic review of current evidence.
“Frankly, I would not actively recommend that consumers take echinacea preparations at the moment,” said lead study author Dr. Klaus Linde of the Center for Complementary Medicine Research, Technical University of Munich.
Echinacea is a top-selling herb in the United States and Europe for the treatment and prevention of colds. The above-ground (aerial) parts of the plant and roots are used fresh or dried to make teas, squeezed (expressed) juice, extracts or preparations for external use. Of the nine known species of echinacea, all native to the United States and southern Canada - the most commonly used, echinacea purpurea, is believed to be the most potent.
“There is some evidence that preparations based on the aerial parts of echinacea purpurea might be effective for the early treatment of colds in adults but results are not fully consistent,” the authors write. They add that the number of echinacea preparations on the market and the different parts of the plant used in each preparation make it more difficult to assess data from clinical trials.
“If someone wants to try echinacea, I would indeed recommend the use, if available, of the products tested positively in clinical trials,” Linde said. “If you use other products, you cannot be certain whether they have a similar composition and effect. Consumers must be aware that ingredients of quality of available products vary greatly - there might be products which are better than those tested, but we don’t know about them.”
The review appears in the most recent issue of The Cochrane Library, a publication of The Cochrane Collaboration, an international organization that evaluates medical research. Systematic reviews draw evidence-based conclusions about medical practice after considering both the content and quality of existing medical trials on a topic.
“My interpretation of the data, including the data on E. purpurea, is that the benefit of echinacea remains to be proven in well-designed studies,” said Ronald B. Turner, M.D., of the University of Virginia.
Turner recently led a study funded by the U.S. National Center for Complementary and Alternative Medicine, that also found echinacea was not effective in preventing colds. “I do not believe echinacea should be recommended as a common cold treatment or preventative based on currently available data. The debate about echinacea is contentious because the data are poor. As described in this review, it is hard to do definitive studies and make clear conclusions because of the great variety and variability of the preparations,” Turner said.
The current review includes 16 clinical trials, 11 of them new, the majority of which compared echinacea to placebo or to no treatment in the prevention or treatment of colds. The most common form of the supplement used in the studies was pressed juices, echinacea suspended in alcohol or tablets made from dried extracts.
The authors write that the latest review provides new information because it includes only studies that used preparations of echinacea that do not contain other herbs.
Studies included participants with viral upper respiratory infections diagnosed as a cold and those with flu symptoms. Six of the studies reported on the duration and severity of symptoms after two to four days of treatment with echinacea, and a statistically significant effect was found for those given the pressed juice from the aerial parts of the plant and echinacea standardized on three bioactive components. In 10 other studies, duration and symptoms were assessed after five to 10 days, and in five of those studies, patients who took the standardized preparation or a high dose of echinacea root extract had colds that resolved more quickly and with less severe symptoms than those on placebo treatment.
The supplement was not shown to be effective in the prevention of colds, and was not effective for treatment or prevention in children. Side effects were mild and rare, and included rash and gastrointestinal disturbances.
“There is clearly some plausibility why echinacea could work; this is true for many herbal drugs,” said Linde. “On the other hand, a lot of money is made by people selling herbal products of questionable quality without research evidence.
“A major problem is that herbal extracts are not patentable. Therefore, if a manufacturer - most of them are rather small - invests huge amounts of money in clinical research on an extract, his competitors can easily use this research for their products, too,” Linde added.
The review notes that of its five authors, four were involved in one of the included studies.
Linde K, et al. Echinacea for preventing and treating the common cold. The Cochrane Database of Systematic Reviews 2006, Issue 1.
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