In the largest clinical trial ever conducted on the popular medicinal herb echinacea, British researchers have concluded that a special Swiss echinacea extract is both safe and effective in helping to prevent symptoms of the common cold.
Researchers tested 755 healthy people to see if the use of an extract of echinacea root and herb was safe and effective in preventing cold symptoms over a four-month period. The randomized, double-blind, placebo-controlled clinical trial used an alcoholic extract of the leaves (95%) and roots (5%) of organically grown echinacea (Echinacea purpurea).
The study took place at the Common Cold Center at Cardiff University in Cardiff, Wales, of the United Kingdom. Healthy subjects were randomized to either echinacea or placebo. At the initial clinical visit, subjects received the extract for one month in addition to completing a diary for documenting potential adverse side effects, incidences of colds and associated symptoms, and the potential use of conventional pharmaceutical medication other than the study treatments. Subjects brought unused treatments and their completed diaries to monthly clinical visits and were also given kits to take nasal swabs for viral identification.
The placebo liquid was comparable in appearance, smell, and taste, with the same percentage of alcohol and identical packaging as the true echinacea extract. The total dosage consisted of 0.9 ml of extract or placebo 3 times per day in water; the subjects were instructed to hold this material in their mouths for 10 seconds in order to achieve maximal local antiviral and anti-inflammatory effects at the pharynx (throat). If subjects had a cold, they were asked to increase dosage from 2,400 mg of the extract daily to 0.9 ml 5 times per day for a total of 4,000 mg of extract.
The results showed that subjects using the Swiss echinacea extract had significantly fewer incidences of cold or flu symptoms (149 colds lasting a combined total of 672 days, while subjects in the placebo group reported 188 colds lasting 850 total days), decreased recurrence of such symptoms (65 vs. 100), respectively), less appearance of influenza-type viral infections, and had to rely less on the use of conventional over-the-counter medicines like acetaminophen or ibuprofen—frequently used by the public to help reduce cold symptoms—than those persons taking the placebo preparation.
An important conclusion of this new study is that even after using the extract for four months, any adverse effects were mild, and because the adverse effects experienced with the echinacea extract were observed to be similar to those in the placebo group, the safety of the extract was evaluated as high. This is consistent with the safety of other echinacea preparations in additional published clinical trials as well as the documented general safety of many echinacea products in general use.
In a summary and critical review of this clinical trial for the nonprofit American Botanical Council’s peer-reviewed journal HerbalGram, author Amy C. Keller, PhD, wrote, “In conclusion…this study claims to be not only the largest ever conducted on clinical effects of echinacea, but the first to employ the detection of specific viruses in this manner. The conclusions from this well-powered, robust clinical trial contribute substantially to the case for the use of echinacea preparations, particularly this specific formulation, in common cold prevention.”
“It is heartening and refreshing to see such positive conclusions coming from this largest echinacea clinical trial ever published,” said Mark Blumenthal, founder and executive director of the American Botanical Council. “While there have been previous clinical studies producing mixed results on the efficacy of various types of echinacea preparations, used at different dosage levels, and in different types of study design, this highly impressive clinical trial is historic due to its size. It employed a high-quality, well-researched echinacea product, a credible study design, and had enough people to produce statistically significant positive results.”
A detailed summary of the new clinical trial can be found in a “Research Review” to be published in the November issue of ABC’s peer-reviewed quarterly journal HerbalGram and currently available online.