The Science Behind Echinacea

Almost everyone has heard of echinacea, an herb best known for its benefits in the treatment of the common cold. But there's more to it. Americans spend well over $100 million annually on this top herbal supplement. But despite echinacea’s long-standing popularity, you may be aware of some controversy regarding its effectiveness for immune support. Here’s how you can lay such concerns to rest—and learn of echinacea’s other potential benefits. Key Constituents There are three species of echinacea commonly used in herbal medicine: Echinacea purpurea, E. angustifolia, and E. pallida (of these, the first two are most popular). The aerial (above ground) parts of the herb as well as the root contain the medicinal components. These include phenolics, caffeic acid esters (e.g., echinacosides), flavonoids, alkylamides, volatile oils, polysaccharides, and polyacetylenes. Evidence-Based Uses Echinacea acts as an immune stimulant and provides excellent support in the prevention and treatment of colds and influenza. Research suggests that echinacea boosts the immune system by activating white blood cells (lymphocytes and macrophages). In addition, echinacea appears to increase the production of interferon, which is important to the immune response of viral infections. A number of double-blind, clinical studies have indicated that echinacea helps alleviate the symptoms of colds and flu. However, some research finds that this herb may be most effective if used at the onset of these conditions. One study involving 238 subjects reported that echinacea was safe and effective in producing a rapid improvement of cold symptoms. In the subgroup of patients who started therapy at an early phase of their cold, the effectiveness of echinacea was most pronounced. In a similar study, 246 subjects with colds were treated with echinacea preparations or a placebo. Those treated with the echinacea preparations experienced a more significant reduction of symptoms than those in the placebo group. The researchers concluded that the echinacea preparations “represent a low-risk and effective alternative to the standard symptomatic medicines in the acute treatment of common cold. The Latest News In a much-publicized study from the July 28, 2005 issue of the New England Journal of Medicine, investigators concluded that echinacea did not have a significant effect on infection with a rhinovirus (one of the 200 viruses that can cause the common cold). This trial’s methodology, however, has been strongly questioned by herbal experts—including myself. Methodological errors include the fact that the study did not use a commercially available product and that the tested dosage was lower than the dose typically used in research and common herbal practice. By contrast, in a recent meta-analysis (a careful, scientific review of many like studies) of 14 trials, researchers at the University of Connecticut School of Pharmacy found that taking echinacea appeared to cut the risk of catching the common cold by 58 percent—and if subjects already had a cold at the trial’s outset, supplementation decreased the duration by an average 1.4 days. In one of the analyzed studies, echinacea taken in combination with vitamin C and propolis reduced cold incidence by 86 percent. When the herbal product was used alone, the incidence of cold was reduced by 65 percent. The bottom line is that, when used appropriately, echinacea is certainly an effective tool in preventing the common cold and improving symptoms. Germany's Commission E Monographs (an internationally authoritative source of credible information on the use of herbs for various disorders) indicates that among echinacea’s other uses, this herb may also be helpful for chronic infections of the respiratory tract. Other current and evidence-based uses of echinacea appear to include vaginal candidiasis; ear, urinary, and sinus infections; and more. Dosage Range and Cautions Typical dosages of this herb are 200 to 400 mg extract with 4 percent total phenolics (including cichoric acid, chlorogenic acid, captaric acid) and/or 4 percent echinacoside, taken three to five times daily for acute infection. Some sources have cautioned that echinacea should not be used with drugs intended to suppress the immune system. Rare allergic reactions may occur in people sensitive to echinacea aerial parts or to the daisy (compositae) plant family.