Echinacea for the Prevention and Treatment of Colds in Adults

On July 28, 2005, The New England Journal of Medicine published the results of a study of Echinacea for the prevention and treatment of the common cold that was funded by the National Center for Complementary and Alternative Medicine (NCCAM).1 The research was conducted by Dr. Ronald Turner, of the University of Virginia School of Medicine, Dr. Rudolf Bauer, Karl-Franzens Universitaet, Graz, Austria, and collaborators at Clemson University in South Carolina.

The research team tested three preparations of the roots of a species of Echinacea called Echinacea angustifolia, which prior smaller studies had found to benefit adults with the common cold. The three preparations were made by extracting the root of E. angustifolia using procedures that represent some of the different ways that Echinacea is available and used to treat the common cold.

E. angustifolia was chosen for the study as it is one of the species endorsed by the World Health Organization for treating the common cold.2 The study was designed to test if Echinacea would help prevent or treat cold symptoms, since this is how Echinacea is often used by consumers.

In the study, 437 healthy adult volunteers were assigned at random to receive one of the three E. angustifolia preparations or a placebo. The volunteers received various combinations of Echinacea and/or a placebo in two phases: a "prophylaxis" (i.e., preventative) phase and a treatment phase. The prophylaxis phase lasted 7 days. On the seventh day, the already treated volunteers were exposed to a nasal spray containing a virus that induces signs and symptoms of a cold in about 2 days. Then, the volunteers were isolated for 5 days while the research team observed and tested them, using state-of-the-art measurements and instruments, as to the appearance and severity of cold signs and symptoms.

In this study, the researchers found that none of the three preparations of E. angustifolia at the 900 mg per day dose had significant effects on whether volunteers became infected with the cold virus or on the severity or duration of symptoms among those who developed colds. However, critics of this study believe the dose of E. angustifolia used was too low.

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