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Herbal Science Group Says Dosage Too Low in New Echinacea Trial


(Austin,TX, July 27, 2005). The nonprofit American Botanical Council (ABC), an Austin,Texas-based research and education organization, has reviewed a new clinicaltrial on the popular herb echinacea for use in a specific kind of induced virus,being published Thursday in the New England Journal of Medicine.1 Thestudy concluded that the echinacea preparations did not prevent or help treatsymptoms of a specific virus applied to the test subjects. ABC has found severalaspects of the design of the study worthy of clarification, and comments on thepotential misinterpretations of the significance of this study.

First,the extracts used were made in a university laboratory and do not correlate withcommercial echinacea products currently available to consumers. Second, the dosagesused in this trial were probably too low. The echinacea preparations used inthe study might have shown activity at more frequent dosing intervals and/orhigher dosage levels - as is often the case with contemporary echinaceause.

The new trial utilized extracts made from the roots of a species of echinaceacalled Echinacea angustifolia. The randomized, double-blind, placebo-controlled,seven-arm trial was conducted on 437 college students who had a particular typeof rhinovirus inserted into their nostrils (the results were calculated on 399subjects). In the trial, the echinacea preparations were tested to see if theyhad a preventive effect or if they could help treat the symptoms caused by therhinovirus. The students who received the three different echinacea preparationsand were sequestered in a hotel room did not experience fewer infections, fewersymptoms, or a reduction in the duration of symptoms, compared with those whoreceived the placebo.

The trial utilized three doses of 1.5 milliliters each ofthe three laboratory-produced echinacea extracts, presumably equivalent to about300 milligrams of the dried powdered root in each dose (equivalent to 900 mgper day of the dried root). This level was chosen for the trial because it isthe dose recommended by the German government’s expert herb panel calledthe Commission E, which had conducted reviews of the research published on varioustypes of echinacea in the scientific and medical literature in the early 1990s.2According to ABC various international monographs have acknowledged the generallyhigher dose used for echinacea root products. The World Health Organization (WHO)monograph for Echinacea root (“Radix Echniaceae”) has a dosage for Echinaceaangustifolia root at the equivalence of 3 gm per day of the dried root.3This same dosage is also acknowledged in the more recently developed draft monographson Echinacea from the Canadian Natural Health Products Directorate.4

Thisdosage level is about 330% higher than the dosage of the echinacea preparationsgiven in the NEJM trial. This supports ABC’s contention that the preparationsmay have been under-dosed and that the trial might have shown a potentially positivetrend if a higher dosage and/or increased frequency of administration had beenfollowed.

“It would have been optimal if this trial had tested the echinaceapreparations at more frequent and/or higher doses,” said Mark Blumenthal,Founder and Executive Director of ABC. “Dosage is one of the most importantaspects in assessing any therapeutic agent. Many clinicians who recommend echinaceafor treatment of upper respiratory tract infections related to colds and flunormally utilize a frequency of use and/or a total daily dose that is higherthan the one used in this trial. This is also true for consumer self-medicationwith many commercial echinacea preparations according to some label dosage suggestions.”

Blumenthaladded. “The researchers have previous experience in researchingechinacea and have done an admirable job in testing a species of echinacea (i.e., E.angustifolia) that has not been adequately researched.” But he hastenedto add, “The most accurate statement that can be said about this trialis this: These specific laboratory-produced echinacea extracts, at the dose givenin the trial, under the specific design of this trial, did not produce any measurableeffect.” He emphasized, “This is not a definitive trial on the efficacy of echinacea,nor should the results be generalized to echinacea preparations widely available.Unfortunately, the conclusion that may be drawn by some media who report thisstudy may state that ‘echinacea is ineffective,’ but this would bean incorrect conclusion based on the design of this study and the evidence inthe existing literature.”

“Dosing people for rhinovirus in a hoteldoes not necessarily mimic real life,” said Bruce Barrett, MD, PhD, anAssistant Professor of Family Medicine University of Wisconsin School of Medicineand an author of several previous critical reviews on echinacea clinical trials.He noted that the patients were possibly relatively resistant to the echinaceatreatment. “Collegekids are immunocompetent,” he stated, referring to the relative healthof the test subjects in the trial. “It may have been better to test olderpeople to see how they might have faired.”However, Dr. Barrett was generally complimentary about the trial in general. “Thisis a very valuable study and quite helpful, although it has some significantlimitations, including product, sample, and population,” he stated. “Ingeneral, you may want to have about 100 people per treatment group for more statisticalsignificance rather than only about 50 per group used in this trial.”

Ingeneral, products marketed as “Echinacea” are extremelypopular in the United States. Echinacea ranked second in sales in mainstreammarket retail stores in 2004, according to an article in ABC’s journal HerbalGram.5Total sales of echinacea products in all channels of trade in the United Statesin 2004 was estimated at about $155 million, according to data compiled by NutritionBusiness Journal. Blumenthal also added that although it was formerly quite popular, therehas been a trend away from using Echinacea angustifolia root in commercialherbal products based on increased concerns by many responsible members of theherb community regarding conservation and sustainability of wild medicinal plants. Echinaceaangustifolia is generally more difficult to cultivate commercially than theother two more popular species of echinacea (E. pallida and E. purpurea),and so more material from these species are found in products on the North Americanmarket.

Blumenthal points to a body of clinical evidence that supports the useof various echinacea preparations for treating symptoms associated with coldsand flus. A therapeuticmonograph on Echinacea isavailable in The ABCClinical Guide to Herbs, ABC’sreference book and continuing medical education module.6 The monograph summarizes21 clinical trials on various echinacea preparations for colds, flus, upper respiratorytract infections, and other uses. ABC has posted the complete echinacea chapterincluding this monograph on its website asan educational service to the public.

Thestudy has generated significant media attention. ABC and Blumenthal have beencontacted by a variety of news sources, including: the Associated Press, BloombergBusiness News, CNN, the Los Angeles Times, NBC Nightly News with BrianWilliams, the New York Times and USA Today.

About the American Botanical Council

The American Botanical Council is the nation's leading nonprofitorganization addressing research and educational issues regarding herbs and medicinalplants. The 17-year-old organization occupies a 2.5 acre site in Austin, Texas,where it publishes HerbalGram ,a peer-reviewed journal. ABC is also the publisher of TheABC Clinical Guide to Herbs,a continuing education and reference book, which contains extensive monographson the safety and efficacy of 29 popular herbs, including echinacea.6 More informationon echinacea is available on ABC’s extensive website,


1. Turner RB, Bauer R, WoelkartK, Hulsey TC, Gangemi DJ. An evaluation of Echinacea angustifolia preparationsin experimental rhinovirus infections. N Engl J Med 2005;353:341-348.

2.Blumenthal M, Busse WR, Goldberg A, Hall T, Riggins CW, Rister RS, eds. KleinS, Rister RS, trans. The Complete German Commission E Monographs - TherapeuticGuide to Herbal Medicines. Boston: Integrative Medicine Communications; Austin,TX: American Botanical Council, 1998.

3. Echinacea Radix. In: WHO monographson selected medicinal plants. Geneva:World Health Organization, 1999.

4. Ehinacea. Natural Health Products Directorate.Health Canada. Draft Jan 2004. Available at: Accessed,Jul 27, 2005.

5.Blumenthal M. Herb sales down 7.4 percent in mainstream market. HerbalGram 2005;66:63.

6.Echinacea. In: Blumenthal M, Hall T, Goldberg A, Kunz T, Dinda K, BrinckmannJ, et al, eds. The ABC ClinicalGuide to Herbs. Austin, TX: American Botanical Council, 2003.