Evidence mixed on the usefulness of echinacea for colds

The six authors conducted reviews on this subject in 1998, 2006 and 2008 and wanted to do an update to include several new trials conducted since then. "We've been doing this for so long and are very familiar with past research -- which has been mixed from the very beginning," said author Bruce Barrett, M.D., Ph.D. in the department of family medicine at the University of Wisconsin in Madison.

The research team reviewed 24 randomized controlled trials to determine whether Echinacea was a safe and effective cold prevention and treatment. Trials included 4631 participants and 33 preparations, along with placebo. Echinacea products studied in these trials varied widely according to characteristics of three different plant species, the part of the plant used and method of manufacturing.

People who get colds spend $8 billion annually on pharmaceutical products, including supplements such as Echinacea, Barrett noted. The authors' meta-analyses suggest that at least some Echinacea preparations may reduce the relative risk of catching a cold by 10 to 20 percent, a small effect of unclear clinical significance. The most important recommendation from the review for consumers and clinicians is a caution that Echinacea products differ greatly and that the overwhelming majority of these products have not been tested in clinical trials.

Barrett added that "it looks like taking Echinacea may reduce the incidence of colds. For those who take it as a treatment, some of the trials report real effects -- but many do not. Bottom line: Echinacea may have small preventive or treatment effects, but the evidence is mixed."

"The paper does support the safety and efficacy of Echinacea in treating colds and highlights the main issue of standardizing herbal medicines," commented Ron Eccles, Ph.D., director of the Common Cold Centre & Healthcare Clinical Trials at Cardiff University's School of Biosciences in Wales.