Echinacea – No Help Against Common Cold?

Studies of Echinacea’s cold-fighting properties show mixed results, with a recent large study1 suggesting no benefit at all. Echinacea did not prevent colds, and it did not ease cold symptoms.

Echinacea is a popular herbal remedy for treating the common cold; however, clinical trials have produced conflicting reports about its effectiveness. Consistent testing of Echinacea is complicated by the fact that a variety of influences, including variable growing conditions of the Echinacea plant, contribute to varying chemical composition between Echinacea preparations.

Native North Americans used the roots of the Echinacea plant (Echinacea angustifolia), also known as “purple coneflower”, to treat a variety of infections and wounds, from snakebites to skin problems such as acne and boils. Echinacea became commercially popular in the late 1800s as a cold remedy, and entered the alternative-therapy commercial mainstream in North America in the 1960s.

The recent study by Turner et al., published in the July 28 issue of the New England Journal of Medicine (NEJM) tested the effectiveness of three different preparations, each with a different plant-chemical composition, of Echinacea against rhinovirus (the virus associated with the common cold).

Study Protocol and Results

A total of 437 volunteers randomly received either preventative treatment with Echinacea (that is, treatment starting seven days before exposure to rhinovirus – also called “virus challenge”) – or treatment with Echinacea (that is, treatment at the time of virus challenge) or placebo. Researchers identified two main efficacy targets: cold prevention and relief of cold symptoms.

Results were taken from 399 volunteers challenged with rhinovirus type 39, who were observed in a closed setting for five days.

No statistically significant differences in infection-rate or symptom severity were seen among volunteers taking any of the Echinacea extracts. Similarly, among treated volunteers, no differences were noted in mucous production volume or in inflammatory markers, such as polymorphonuclear leukocyte or interleukin-8 concentrations in nasal-lavage specimens.

Study results therefore indicate that Echinacea extracts do not offer clinically significant health benefits against the common cold.

In an accompanying editorial2 in the NEJM, Dr. Wallace Sampson of Stanford University argues that the study’s findings should warn against using Echinacea as an effective cold remedy. Dr. Sampson is Editor of Scientific Review of Alternative Medicine.

Because this was a large, multi-centered, randomized, blinded trial, Dr. Sampson notes that, “…unless some obscure protocol violation occurred, the trial results are real."

Turner et al.’s clinical trial was supported by the National Institutes of Health’ National Center for Complementary and Alternative Medicine (NCCAM), which has three additional clinical trials of Echinacea underway, according to Dr. Sampson.

References:

  1. An Evaluation of Echinacea angustifolia in Experimental Rhinovirus Infections, Ronald B. Turner et al., New England Journal of Medicine, Volume 353(Number 4):341-348, July 28, 2005.
  2. Studying Herbal Remedies, Wallace Sampson, MD, New England Journal of Medicine, Volume 353:337-339(Number 4), July 28, 2005.

Posted: August 2005


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