Echinacea does not prevent or help treat the common cold

Main Category: Complementary Medicine / Alternative Medicine
Also Included In: Preventive Medicine
Article Date: 01 Aug 2005 - 5:00 PDT

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The New England Journal of Medicine published the results of a National Center for Complementary and Alternative Medicine (NCCAM)-funded clinical trial of echinacea for the prevention and treatment of the common cold. The researchers were from the University of Virginia School of Medicine, Charlottesville (principal investigator Ronald B. Turner, M.D.), Karl-Franzens Universitaet, Graz, Austria, and Clemson University, Clemson, South Carolina. An abstract summarizing this randomized, double-blind, placebo-controlled study is posted on the The New England Journal of Medicine Web site.

The research team tested three laboratory-made preparations made from the roots of a species of echinacea called Echinacea angustifolia. The extracts were made at three different strengths that are most represented in the worldwide literature on echinacea for the common cold. This design allowed clinical effects from different strengths of echinacea to be observed.

Four hundred and thirty-seven healthy, young-adult volunteers were assigned at random to receive either one of the echinacea preparations or a placebo. There were seven subgroups among the volunteers that 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 mist containing common-cold virus. Then, they were isolated for 5 days while the team observed and tested them, using state-of-the art measurements and instruments, as to the appearance and severity of cold symptoms.

The team found that taking echinacea had no clinical or significant effects on whether volunteers became infected with a cold or, in those who developed colds, on how severe their symptoms were or how long those symptoms lasted.

Stephen E. Straus, M.D., Director of NCCAM, offered the following comments:

Echinacea is a popular therapy within the area of complementary and alternative medicine (CAM). In fact, a 2004 national survey on CAM use by Americans found that among those who used natural products, echinacea was the most popular product that they used.

The common cold is a major burden on society, and there is not much that conventional medicine can do to prevent it or ease its symptoms. Thus, there is a lot of appeal in the idea of a readily available remedy that might prevent us from getting a cold or make us feel better if we do get one. However, it's important to ask whether science has proven that echinacea really does work for these purposes.

This well-designed study, led by a team with expertise in the preparation and study of herbal medicines and the treatment and prevention of respiratory virus infections, clearly showed that echinacea did not prevent or treat the common cold. These results confirm and extend those of a previous NCCAM study published in 2003 that found a popular echinacea product was not effective in treating colds in children.

There have been criticisms of many prior studies of herbal supplements, such as products not being consistent, dosages being too low or infrequent, or treatment having been started too late or too soon. However, this study addressed these issues through testing to ensure the echinacea products were chemically consistent throughout the study, using internationally recognized doses, and using the current most-powerful approach for testing treatments for the cold virus.

NCCAM is supporting other studies to find out more about echinacea and about other biologically based CAM therapies. These range from studies in the laboratory, to studies carefully establishing dosages, to studies of these therapies for diseases and conditions, building on promising and compelling earlier evidence.

Preparations of echinacea, like any herb, can be variable--what's on the label may not always be what's in the bottle. In addition, herbs are biologically active, so there can be side effects or potential herb-drug interactions. Talk with your health care provider if you are using herbal products or are thinking about using them.

References:

Turner RB, Bauer R, Woelkart K, et al. An evaluation of Echinacea angustifolia in experimental rhinovirus infections. The New England Journal of Medicine. 2005 353(4): 341-348.

Taylor JA, Weber W, Standish L, et al. Efficacy and safety of echinacea in treating upper respiratory tract infections in children: a randomized controlled trial. Journal of the American Medical Association. 2003 290(21):2824-2830.

nccam.nih.gov/clinicaltrials/echinacea_rr.htm