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Echinacea and the Common Cold
What is Echinacea?
Echinacea, a member of the daisy family, is an herb with bright pink or purple flowers. In the center of the flower is a large seed head, usually purple-brown in color, with sharp spines. Nine species of Echinacea grow in the United States, and three of them (Echinacea angustifolia, Echinacea pallida, and Echinacea purpurea) are used for medicinal purposes.
What are People Saying About Echinacea?
According to various websites on the internet, Echinacea boosts the immune system and helps the body fight infections. It is thought to prevent colds, the flu, and upper respiratory infections. Echinacea supposedly reduces the duration of these illnesses as well the symptoms, including cough, runny nose, enlarged lymph glands, fever, and sore throat.
How it Works
Polysaccharides are frequently cited as the active ingredients in Echinacea.
According to http://www.herbs.org/greenpapers/echinacea.html, Echinacea reportedly increases the number and activity of immune system cells. It also reportedly “…inhibits the bacterial enzyme hyaluronidase, which helps prevent bacterial access to healthy cells.”
A second website, http://www.primary.net/~gic/herb/echin.htm, states that the most important components of the herb are large polysaccharides, including inulin, which increase the production of T-cells (a type of white blood cells involved in the body’s immune system).
According to the site, “Fat-soluble alkylamides and a caffeic acid glycoside called echinacoside also contribute to the herb's immune empowering effects.”
Another page, http://www.umm.edu/altmed/ConsHerbs/Echinaceach.html, claims that a combination of polysaccharides from the above-ground part of the herb and volatile oils from the roots make Echinacea an effect immune system booster.
Who Presents This Information?
Websites making these claims about the effectiveness of Echinacea include:
The purpose of these websites is to sell Echinacea to consumers, either in tablet form or combined with other ingredients to create immune-boosting products. In other words, they are maintained by companies whose primary aim is to make money. Of course they tell consumers that their product works! Information obtained from these sites is not necessarily factual and include questionable (if any) references to “scientific” studies.
Echinacea seems to be a relatively safe herb. Side effects are limited and include possible upset stomach and a tingling sensation in the mouth. According to http://www.umm.edu/altmed/ConsHerbs/Echinaceach.html, Echinacea should not be used by people with tuberculosis, leukemia, diabetes, connective tissue disorders, multiple sclerosis, HIV or AIDS, autoimmune diseases, or liver disorders. Allergic reaction is rare but can occur. Also, Echinacea should not be used for more than eight weeks because it stops working and may actually dampen immune system functioning.
What Does Science Say About Echinacea?
Echinacea and Preventing the Common Cold
Scientific studies found that Echinacea is not an effective form of prevention for colds. Turner (2000) treated some participants with Echinacea three times a day for 14 days prior to exposing them to a strain of rhinovirus (the common cold), while a control group received a placebo. The experimental group continued to take the herb for five days after exposure to the cold virus. This study found no statistical differences in the number of individuals who came down with a cold, regardless of whether they received Echinacea or a placebo. There was also no difference in the severity of cold symptoms between the two groups.
Additionally, a study by Sperber et al. and referenced by Zemf (2005) used a similar method. They treated their experimental group with Echinacea three times a day for seven days before inoculating the participants with rhinovirus, and then continued the Echinacea treatment for an additional seven days. The control group received a placebo for all 14 days. Sperber et al. found no difference between the treatment and control group in the number of participants who got a cold.
A third and more complex study by Turner (2005) distributed Echinacea to participants at different points in the experiment. Some participants received the herb three times a day for seven days before the introduction of rhinovirus while others received Echinacea three times a day for five days following exposure to a cold. One group of individuals took Echinacea three times a day both before and after being exposed to the rhinovirus while another received a placebo the whole time. Different groups of participants also received different concentrations (strengths) of Echinacea. Turner (2005) found no significant effects of Echinacea in preventing colds or minimizing the symptoms, regardless of when it was taken or the concentration taken.
Echinacea and Relieving Symptoms of the Common Cold
As illustrated by the Turner (2000, 2005) studies, Echinacea does not appear to be effective in relieving symptoms of the common cold. There was also no difference between the experimental and control groups in the duration of their cold symptoms.
In another study by Yale (2004), participants in the treatment group received Echinacea three times a day at the onset of a cold. They continued taking the herb in this way until their symptoms stopped or at the end of 14 days, whichever came first. The control group took a placebo three times a day for the same amount of time. Participants rated and recorded their symptoms and the severity of their symptoms daily. Yale (2004) found no statistically significant difference in symptom scores or in the time resolution of the cold symptoms between the two groups.
Echinacea in Different Forms
These studies tested different species of Echinacea, experimented with different doses, and administered the herb in different forms (tablet, liquid, tincture, etc.).
Turner (2005) conducted his study using E. angustifolia while Yale (2004) utilized E. Purpurea. As previously stated, neither author found statistically significant differences in the participants taking Echinacea and those taking a placebo.
Yale (2004) gave their participants 100mg doses of Echinacea three times a day, while Turner (2005) provided 300mg doses. Again, neither author found that Echinacea is an effective medication.
Finally, most studies provided Echinacea in tablet form. However, the study by Sperber et al. and referenced by Zempf (2005) distributed Echinacea as a liquid and another study by Turner (2005) distributed Echinacea as a tincture (mixed in with alcohol). Neither author found that Echinacea in these various forms was any more effective in treating or preventing colds. In other words, there is no difference in the efficacy between tablets, liquid, and tincture forms of Echinacea.
Literature reviews (which analyze the available scientific research) by Knight (2005) and Caruso and Gwaltney (2005) also deny the efficacy of Echinacea in treating and preventing colds. Both authors point out that studies claiming to find positive results don’t actually meet clinically based criteria; in other words, they aren’t valid clinical trials or experiments. According to Caruso and Gwaltney, the most common problem is that the experiments are not blind. This means that the subjects knew whether they received placebo pills or Echinacea. Knowing what group they are in (ie whether or not they are receiving an actual treatment) can make a huge difference in what participants report to the researcher. This is called the placebo effect, and it ruins the worth of an experiment.
The Bottom Line
Research studies and literature reviews on the effectiveness of Echinacea are unanimous: Echinacea is not effective for the prevention or treatment of the common cold.
Taylor, J., Weber, W., Standish, L., et al. (2003). Efficacy and safety of Echinacea in treating
upper respiratory tract infections in children: a randomized controlled trial. JAMA, 290, 2824 – 2830.
Yale, S.H., & Liu, K. (2004). Echinacea purpurea therapy for the treatment of the common cold:
a randomized, double-blind, placebo-controlled clinical trial. Arch Intern Med, 164,
1237 – 1241.
Knight, V. (2005). Echinacea treatment for the common cold. Clinical Infectious Diseases,
40(6), 811 – 812.
Caruso, T.J., & Gwaltney, J.M. Jr. (2005). Treatment of the common cold with Echinacea: a
structured review. Clinical Infectious Diseases, 40(6), 807 – 810.
Zepf, B. (2005). Echinacea for prevention and treatment of colds. American Family Physician,
71(4), 800 – 801.
Turner, R.B., Riker, D.K., and Gangemi, J.D. (2000). Ineffectiveness of Echinacea for
prevention of experimental rhinovirus colds. Antimicrobial Agents and Chemotherapy,
44(6), 1708 – 1709.
Turner, R.B., Bauer, R., Woelkart, K., Hulsey, T.C., & Gangemi, J.D. (2005). An evaluation of
Echinacea angustifolia in experimental rhinovirus infections. The New England Journal of Medicine, 353(4), 341 – 351.
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