Herbal remedies continue to grow in popularity in the U.S. as demonstrated by expanding sales with seemingly no correlation to scientific research. Echinacea preparations have developed into the best-selling herbal immunostimulants. Nine species of the genus Echinacea are found today in the U.S. and Canada. Native Americans used Echinacea to treat wounds, snakebites and other animal bites, tonsillitis, headache, and cold symptoms. In the early 1900s in the U.S., Echinacea was the most utilized indigenous medicinal plant. After the introduction of antibiotics, its use declined in the U.S., although today it remains popular in Europe.
Although Echinacea is processed and sold around the world, Switzerland and Germany have been in the forefront by marketing more than 800 homeopathic products and drugs containing Echinacea (). Analyses of these preparations have shown that three different species of Echinacea are used in medicine and homeopathy: Echinacea angustifolia DC, Echinacea pallida (Nutt.) Nutt., and Echinacea purpurea (L.) Moench. (Asteraceae). Even though a number of species of Echinacea have shown an immunostimulating effect, E. purpurea has been the type most often used for relief of symptoms of flu, cold, and upper respiratory illnesses. When the aqueous extracts of the aerial parts of the E. purpurea were subjected to systematic fractionation and pharmacological testing, the result was the isolation of two polysaccharides with immunostimulating properties. These polysaccharides were found both to stimulate phagocystosis in vitro and in vivo, and to augment the production of oxygen radicals by macrophages in a dose-dependent manner. Problems with analyses of these components continue since the methods are still evolving. Polysaccharides in Echinacea are analyzed through specific determination by isolation and structure elucidation or by nonspecific determination by hydrolysis of monosaccharides; neither of these methods is yet commercially obtainable. E. angustifolia (a component of Echinacea Plus®) has also been shown, when combined with other types of Echinacea, to have an immunostimulating effect in relieving cold and flu symptoms.
Researchers have studied various time intervals for Echinacea in the prevention and treatment of cold and flu symptoms. Some differences have been determined in research findings on the efficacy of Echinacea as a prophylactic over time. In a 6-month double-blind placebo study, the Echinacea treatment group had fewer respiratory reinfections (19% vs. 32%), an increase in time interval between such reinfections (25 vs. 40 days), a reduction in the average length of colds (5.3 vs. 7.5 days), and less severe symptoms. Grimm and Muller, however, found that Echinacea taken prophylactically during a 3-month period did not significantly decrease the incidence, duration, or severity of colds compared to a placebo. There is also conjecture, but no formal research findings, that Echinacea reduces the strength of the immune system response when used continuously over time.
Recent research has to a great extent concentrated on early Echinacea intervention for relieving the symptoms and duration of colds and flu-like infections. For example, Braunig et al. demonstrated a statistically significant improvement of symptoms over placebo with early intervention, that is, when symptoms first appear. Hoheisel et al. in a randomized, double-blind, single-center placebo-controlled study demonstrated that the use of an expressed juice of E. purpurea, given orally from the onset of the initial symptoms of an upper respiratory infection or cold, inhibits the full expression of the infection and, moreover, shortens the recovery time. Melchart et al. conducted a meta-analysis of 26 controlled clinical trials (18 randomized, 11 double blind) on the immunomodulatory effects of Echinacea; 16 of the 18 randomized trials claimed positive results, suggesting that preparations containing extracts of Echinacea can be clinically effective immunomodulators. Melchart et al. subsequently reviewed 16 trials and found that some Echinacea compounds may have stronger effects than a placebo. Most of the research studies showed positive results but without enough evidence to support any specific Echinacea product. Another issue has been that of the efficacy of tablet vs. liquid extract. Quite a few articles and research studies have reviewed the digestibility and absorption of the tablet forms of Echinacea. The majority of researchers agree that the liquid forms, either in a tea or an alcohol base, are best for maximum absorption and thus maximum efficacy (British Herbal Medicine Association).
In a research study, Lindenmuth tested the efficacy of an Echinacea-compound herbal tea compound on duration and severity of symptoms of cold and flu — specifically, scratchy throat, runny nose, and fever — using a randomized double-blind study. Subjects of the study were employees of Rest Haven-York Nursing and Rehabilitation Center, a 167-bed facility in York, PA. Employees were eligible for the study if they reported the earliest symptoms of cold or flu: runny nose, scratchy throat, or fever. Persons excluded from the study were pregnant women, nursing mothers, those with known allergies to coneflowers, those who stated that they were allergic to any flowering plants or pollens, and those with acute infections and already taking antibiotics.
In December 1998, employees of the nursing and rehabilitation center were advised of the study and received information sheets about Echinacea. They were informed that from 1 January 1999 through 30 March 1999, at the earliest sign of a cold or flu symptoms (runny nose, scratchy throat, fever) they could on a voluntary basis be participants in an experimental research study for the purpose of testing the effectiveness of Echinacea. Those persons with symptoms who volunteered to be in the study were then randomly assigned throughout the time period to either the experimental group (Echinacea) or control group (placebo). The assignment was conducted by specially trained secretarial personnel not associated with the study who had no knowledge of which of two boxes contained packets of Echinacea Plus or Eaters Digest (placebo) tea bags. Upon reporting to the secretarial personnel, each subject received a packet containing 21 tea bags of like appearance (wrappings) of either Echinacea Plus or the placebo. Subjects were assigned numbers, as were the boxes of tea bag packets.
The herbal dietary supplement, Echinacea Plus, was prepared and packaged by Traditional Medicinals®, Inc. of Sebastopol, CA. Echinacea Plus contains a proprietary blend of the leaves, flowers, and stems of organically grown E. purpurea and E. angustifolia, plus a water soluble dry extract of E. purpurea root (6:1). In combination, this delivers the equivalent of 1.275 mg of dried herb and root per tea bag serving. When prepared according to label directions, a minimum of 31.5 mg of total phenolic compounds (calculated as caftaric acid, cichoric acid, chlorogenic acid, and echinacoside) are yielded into one dose of brewed tea, as determined by high-performance liquid chromatography (HPLC). The herbal mixture additionally contains small amounts of two adjuvant components, lemongrass leaf (Cymbopogon citratus [DC. ex Nees] Stapf.) and spearmint leaf (Mentha spicata L.). At higher dosages these components might have an effect; however, both lemongrass leaf and spearmint leaf occur in the formula as “flavor corrigents,” which are allowed in an herbal tea formula at up to 20% of the formula. This makes the tea palatable in order to ensure patient compliance and tolerance; mint leaf is a widely used flavor corrective in medicinal herbal preparations.. Specific instructions for boiling, steeping, and dosage were given to each subject as follows: Pour 8 oz. of boiling water over one tea bag and steep, covered, for 10 to 15 minutes. Drink 5 to 6 cups on the first day of symptoms, titrating to 1 cup by the 5th day.
The placebo for the control group, “Eater’s Digest” herbal tea from Traditional Medicinals, was chosen because the product promotes healthy digestion and has no history of having any effect on cold or flu symptoms. The cinnamon, ginger, and peppermint inclusions could possibly have an effect if given in a higher dosage; in the indicated amounts, they serve as flavor correctives. Moreover, this tea contains no stimulants and has no obvious or easily recognizable aroma or flavor characteristics that would cause it to be easily discernible from the Echinacea Plus tea by a person with an untrained palate. Subjects would not be likely to have the capability to determine the taste of the Echinacea compound, especially since the tea is a multiherb formula containing mint leaf. Furthermore, both the treatment group and control group teas in this study contained mint leaf. A natural flavor could have been added to both teas in an attempt to mask any recognizable or known characteristic flavors, but the problems with that approach are twofold. Subjects may have needed to believe that they were drinking medicinal herbal tea; a flavored tea might have had an influence on the results due to generally not being perceived as medicinal. Second, by adding an ingredient to the existing formula, the drug being studied is no longer the same as the drug in commerce (Echinacea Plus). Additionally, each tea bag (treatment and control) was specially wrapped in the same lining and paper to prevent olfactory and visual differentiation by subjects.
The control tea contained peppermint leaf (Mentha x piperita Linne); sweet fennel seed (Foeniculum vulgare Miller ssp. vulgare, var. duke [Miller] Thellung); ginger rhizome (Zingiber officinale Roscoe); rose hip (Rosa canina L.); papaya leaf (Caricapapaya L.); alfalfa leaf (Medicago saliva L.); and cinnamon bark (Cinnamomum cassia J. Presl.). Directions for preparation given subjects in the control and treatment groups were the same.
Braunig and Knick reported a study in which a daily dosage of 90 drops of a hydroalcoholic tincture (1:5) (equal to 900 mg of dried Echinacea root) is effective in reducing cold-type symptoms in comparison to a daily dosage of 450 mg of dried Echinacea root in a second group. Traditional Medicinals recommends 3 to 5 cups per day of the Echinacea formula, containing 1000+ mg of Echinacea per cup of tea (one bag). The protocol for this study was established at 5 to 6 cups of the tea on the first day of symptoms, titrating to 1 per day for the last of the 5 days. The control (placebo) group was placed on the same schedule.
A questionnaire was designed in a brief format in order to encourage subjects to not only complete it but also to do so with accuracy. It was administered to each subject 14 days after having started the program. Question 1 addressed the effectiveness of the tea in relieving cold or flu symptoms; question 2 requested the number of days that cold and flu symptoms lasted; question 3 asked for the time it took for the subjects to notice any difference in their symptoms. Our hypotheses anticipated a significant difference in effectiveness of relieving cold or flu symptoms between the experimental group (Echinacea) and control group (placebo), a significant difference between the experimental group (Echinacea) and control group (placebo) in the number of days the symptoms lasted, and a significant difference between the experimental group (Echinacea) and control group (placebo) in the number of days it took for subjects to notice a change. Means, standard deviations (SDs), and f-tests were run for each question. Confidence intervals of 95% were utilized with statistical significance set atp < 0.05 level (two-tailed).
The experimental group was comprised of 48 people, and the control group, 47. Ninety-three percent of all employees were women; women accounted for 41 and 40 subjects in the experimental and control groups, respectively. Age ranged from 24 to 62, with a mean age of 39.7, a median age of 40, and a mode of 28. Subjects included RNs, LPNs, maintenance personnel, nurses’ aides, dietary staff, therapists, administrators, accountants, and MDs. Rest Haven-York Nursing and Rehabilitation Center is located between an inner city area and a suburban area. The participants live in suburban and rural areas (60%) and the inner city (40%). All subjects who began the study completed the tea regimen and the questionnaire, and were included in the analyses. All subjects reported that they followed the dosage directions exactly.
The statistical analyses of the elements of the questionnaire showed the following:
- Question 1: There was a significant difference between the experimental group (Echinacea) vs. the control group (placebo). Experimental group mean = 4.125, SD = 0.9593; control group mean = 2.787, SD = 0.9541; t = 6.814; p < 0.001.
- Question 2: There was a significant difference between the experimental group (Echinacea) vs. the control group (placebo). Experimental group mean = 4.333, SD = 0.9302; control group mean = 2.340, SD = 1.088; t = 9.499; p < 0.001.
- Question 3: There was a significant difference between the experimental group (Echinacea) vs. the control group (placebo). Experimental group, mean = 3.854, SD = 0.9735, control group, mean = 2.297, t = 6.865; SD = 1.204, t = 6.865; p < 0.001.
The Efficacy of Echinacea Tea: Discussion
The efficacy of E. purpurea and E. angustifolia combined in tea form was tested in this randomized double-blind placebo-controlled experiment. The issues were the evaluation of any changes in the severity of cold or flu symptoms and any change in the amount of time for an effect to appear. Statistically evaluated treatment with the Echinacea compound tea taken at the early onset of symptoms was effective at relieving the severity of cold or flu symptoms in a shorter period of time and was noticeably quicker than the placebo in number of days until it had an effect.
During the introduction of the study to the staff, which included the distribution of educational material on Echinacea, the intent was that all potential subjects (whether in treatment or control groups) would be under the impression that the tea would have an effect. This along with randomization and scrutinized, effective controls in the double-blind study reduced the likelihood of extraneous errors. Thus, the differences between the two groups found on the three questions are more likely derived from the independent variable than error or chance.
Interviews after the completion of the questionnaire showed that those in the Echinacea group reported that their acute symptoms of stuffiness, scratchy throat, and fever seemed to subside within a day or two and with only a “slight drip” remaining. The control group, however, reported acute symptoms lasting 6 to 10 days with little or no relief. None of the subjects reported any side effects. The Rest Haven-York Nursing and Rehabilitation Center experienced 28.7% less absenteeism than in the previous year. These results were not tested for statistical significance due to confounding variables such as varying severity in different flu and cold seasons and changes in the employee population over the study period.
The findings of the study must be interpreted within the context of the study’s limitations. The sample was not representative of the population. Since participation in this study was almost exclusively female, it may be inappropriate to generalize the results in terms of both males and females. There is also the concern of all subjects working in the healthcare field and due to that perhaps differing from the general population. A further limitation may be found in the alternation of the assignment process for group formation; it was accomplished in this manner, first, because the ultimate sample size, i.e., individuals with symptoms, could not be predetermined and second, for the maintenance of the double blind and ease for research assistants conducting the study. The questionnaire has shortcomings due to design simplicity, chosen in order to encourage completion of the survey by all subjects irrespective of their educational level. Although limiting, an assessment device without evaluation of level of symptoms was beneficial for the purpose of not confounding the results with extraneous variables such as degrees of cold or flu. A further limitation is associated with the concept of the self-report device; the self-reporting of cold and flu symptoms and their relief has the usual problems associated with self-report methods. Since self-reports were also used in the control group, this bias is perhaps minimized.
Healthcare professionals and the general public have been seeking more scientific research studies on herbal remedies. It appears at this time that when administered at early onset of symptoms, Echinacea reduces the duration and alleviates cold and flu symptoms. Future empirical studies are needed to continue to evaluate the benefits of Echinacea through manipulation of type of Echinacea, of dosage amount, and of dosage timing. As more research is completed and published there will be increased understanding in terms of efficacy.
Selections from the book: “Echinacea. The genus Echinacea”. Edited by Sandra Carol Miller. Series: “Medicinal and Aromatic Plants — Industrial Profiles”. 2004.