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Echinacea: Mixed results from recent trials

The research record on echinacea for the treatment and prevention of colds paints a confusing picture, with tantalizing clues to mechanisms of action and a combination of clinical and laboratory evidence of immune system stimulation. The most recent studies do little to clear the record, but present a mostly positive outcome. Perhaps the most compelling conclusion to be drawn from a review of the following three recent studies is that echinacea appears to work more effectively when taken at the first sign of a cold than when used as a daily preventative.

The first of these recent studies failed to support the use of daily doses of echinacea extract for preventing the common cold [Melchart et al., 1998]. In this double-blind, placebo-controlled German clinical trial involving more than 300 healthy volunteers, extracts of roots of Echinacea angustifolia DC, Asteraceae and E. purpurea (L.) Moench were not significantly better than placebo in preventing colds. The 12-week trial was intended to test the prophylactic (preventive) effect of the two different echinacea species against colds, with participants recruited from four military sites and one factory. Over the course of the study, each took 50 drops of echinacea extract (1:11, 30% alcohol) or placebo twice a day from Monday to Friday, and recorded any cold symptoms during the test. The two echinacea groups did experience fewer colds, but the difference was too slight to be statistically significant. In the placebo group, 37 percent caught colds, compared to 32 percent of those taking E. angustifolia and 29 percent of those taking E. purpurea. Although this result does not meet the criteria for statistical significance, the authors noted that echinacea may have provided a protective effect of about 10 to 20 percent. They also noted that in other trials, echinacea taken at the first sign of a cold significantly reduced the number of people who developed a "full" cold and decreased the duration of symptoms. Many echinacea users and herbalists believe that using echinacea at the first sign of a cold is more effective than long-term daily use. There are also questions concerning the dosage used in this study. The 1:11 extract used by the researchers is less than half the strength of the 1:5 extract used in the often-cited 1992 study by Braunig et al., which demonstrated that E. purpurea root had a significant effect on reducing the duration and severity of colds and flu.

Another placebo-controlled, double-blind study offers a much more positive outlook, based not on daily preventive echinacea use but on an early intervention model [Brinkeborn et al., 1998]. In this Swedish trial, 199 patients with colds took echinacea extract or placebo at the first sign of a cold. Physicians judged echinacea extract effective in 68 percent of cases, and 78 percent of patients considered it effective. The hydroalcoholic extract of fresh E. purpurea aerial parts (95%) and roots (5%) was taken in doses of two tablets three times a day over a period of eight days. The tablets contained a dosage of extract equivalent to around 240 mg of echinacea per day. Patients and physicians agreed that the preparation (Echinaforce®, Bioforce AG, Switzerland) "resulted in a clearly greater reduction in clinical symptoms than that seen with placebo."

This study, supervised by infectious disease specialist Dr. R. Brinkeborn, was also significant in that it concentrated on volunteers who considered themselves especially susceptible to colds. Patients were instructed to begin taking the echinacea extract at the first sign of a cold, and both patients and physicians evaluated effectiveness on the basis of ratings of 12 specific cold symptoms. It should be noted that placebo was judged effective by physicians in around 40 percent of cases and by patients in nearly 50 percent of cases. However, the superior showing in the echinacea group was statistically significant, and the authors concluded that echinacea "may be recommended as well suited to the treatment of colds in the acute stage."

Following a similar treatment protocol, a Swedish and German research team reported positive results from the use of an echinacea preparation (Echinagard®, Nature's Way, Utah) consisting of squeezed sap of E. purpurea [Hoheisel et al., 1997]. Sixty percent of those who took echinacea at the first sign of a cold avoided developing full colds, and those who did recovered quickly. In this randomized, double-blind, placebo-controlled clinical trial, 120 patients with initial cold symptoms took 20 drops of the echinacea preparation every two hours for the first day, and three times a day thereafter for up to 10 days. According to patient evaluations, the symptoms progressed to a "real" cold ("i.e., fully expressed disease") in only 40 percent of those taking echinacea, compared to 60 percent of those in the placebo group. In addition to a 20 percent reduction in the numbers who experienced "real" colds, those in the echinacea group who did experience significant symptoms recovered from their colds twice as fast (four days versus eight days in the placebo group).

This study included only persons especially susceptible to colds, each having experienced three or more respiratory infections in the six months before the study. The authors concluded that the echinacea preparation tested "is a safe and effective therapy when taken at the first signs of a common cold." - Rob McCaleb (HRF)

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[Braunig B, Dorn M, Knick E. Echinacea purpureae radix for strengthening the immune response in flu-like infections (German). Zeitschrift für Phytotherapie 1992; 13: 7-13.

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Brinkeborn R, Shah D, Geissbühler S, Degenring FH. Echinaforce® in the treatment of acute colds. Schweiz Zschr GansheitsMedizin 1998; 10: 26-29.

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Hoheisel O, Sandberg M, Bertram S, Bulitta M, Schäfer M. Echinagard treatment shortens the course of the common cold: a double-blind, placebo-controlled clinical trial. European Journal of Clinical Research 1997; 9: 261-268.

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Melchart D, Walther E, Linde K, Brandmaier R, Lersch C. Echinacea root extracts for the prevention of upper respiratory tract infections. Archives of Family Medicine 1998; 7: 541-545.]

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