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Echinacea for Prevention and Treatment of Adults' Colds
On July 28, 2005, the New England Journal of Medicine published the results of an NCCAM-funded clinical trial of echinacea for the prevention and treatment of the common cold in adults. The research was conducted by Dr. Ronald Turner, of the University of Virginia School of Medicine; Dr. Rudolf Bauer, Karl-Franzens-Universität, Graz, Austria; and collaborators at Clemson University in South Carolina.
In this study, the research team found that none of three different preparations of the root of Echinacea angustifolia at 900 mg per day had significant effects on whether volunteers became infected with a cold virus, or on the severity or duration of symptoms among those who developed colds. The study included 437 healthy adult volunteers who were assigned at random to receive one of the echinacea preparations or a placebo. (There are critics of this study who believe that the dosage of echinacea used was too low.)
The trial was designed to test if echinacea would help prevent or treat cold symptoms, because this is how echinacea is often used. Echinacea angustifolia was chosen as it is one of the species endorsed by the World Health Organization for treating the common cold. Earlier, smaller studies had found that the three preparations used benefited adults with the common cold, and these preparations represent some of the different ways that echinacea is available and used for colds.
Research on botanicals, including echinacea, presents a number of challenges in terms of determining the product's active elements, standardizing the product, and deciding on an appropriate dosage. Challenges to echinacea research include:
- Determining whether the roots, leaves, flowers, seeds, or stems are the most effective parts of the plant
- Investigating the differences between echinacea species
- Determining the proper dose
It is only after these questions have been answered and standardized echinacea preparations have been developed that additional large-scale studies in people can be conducted.
NCCAM will continue to support research on echinacea. A number of smaller studies are currently under way. This research is being done both because of the public health burden of the common cold and the public's widespread use of echinacea. A recent survey of CAM use by U.S. adults found echinacea is the most commonly used natural product.
