Written by Susan Sweeny Johnson, PhD, Biochem. This literature review suggests that Echinacea can be effective in reducing incidence and duration of the common cold.
Although Echinacea extracts are commonly used for treatment and prevention of colds, (1,2) some studies have not demonstrated a clear benefit. (3) In this literature review, researchers sought to establish whether the species of Echinacea used (E purpurea or E angustifolia), the addition of other supplements to the study, or the method of exposure to cold viruses affected the results of studies of cold duration and incidence.
The researchers selected 14 placebo controlled studies for their analysis encompassing 1356 study participants for incidence and 1630 participants for duration of colds. When all studies were taken together, statistical analysis showed that echinacea decreased the odds of a patient contracting a cold by 58% and decreased the duration of colds by 1.4 days within a 95% confidence interval.
Regardless of whether echinacea was administered in the presence or absence of other supplements, substantial reductions in the incidence of the common cold were seen. Significantly, one study included in the analysis used Vitamin C and propolis along with Echinacea extract and the incidence of cold was reduced 86%.4 Vitamin C is commonly thought to aid in cold therapy and may improve the results of this study.
When study participants were exposed to colds naturally, the Echinacea group showed a 65% reduction in cold incidence but when they were specifically exposed to rhinovirus, the Echinacea group only showed a reduction in incidence of 35%. Researchers suggest that Echinacea may not be as effective against rhinovirus as other cold viruses.
One of the most well known studies is Taylor (2005) (3) in which patients received 900mg of E angustifolia per day and showed no reduction in incidence of cold when exposed to rhinovirus. It should be noted that E purpura, not E angustifolia is approved by the German Commission E5 and the WHO recommends 3 gm per day, (6) three times that used in this study.
In conclusion, the literature review suggests that Echinacea can be effective in reducing incidence and duration of the common cold. Further studies of incidence and duration of cold using consistent species and dosage of echincea and using a controlled method of exposure to cold viruses are needed to firmly establish its benefit.
Source: Shah, Sachin A., Stephen Sander, C. Michael White, Mike Rinaldi, and Craig I. Coleman. “Evaluation of echinacea for the prevention and treatment of the common cold: a meta-analysis.” The Lancet infectious diseases 7, no. 7 (2007): 473-480.
© 2007 Elsevier Ltd. All rights reserved.
Posted August 22, 2008.
References:
- Caruso TJ, Gwaltney JM Jr. Treatment of the common cold with echinacea: a structured review. Clin Infect Dis 2005; 40: 807–10.
- Health Canada. Echinacea angustifolia: natural health products directorate. Draft January, 2004.
- Turner RB, Bauer R, Woelkart K, Hulsey TC, Gangemi JD. An evaluation of Echinacea angustifolia in experimental rhinovirus infections. N Engl J Med 2005; 353: 341–48.
- Cohen HA, Varsano I, Kahan E, Sarrell EM, Uziel Y. Eff ectiveness of an herbal preparation containing echinacea, propolis and vitamin C in preventing respiratory tract infections in children: a randomized, double-blind, placebo-controlled, multicenter study. Arch Pediatr Adolesc Med 2004; 158: 217.
- Blumenthal M, Busse WR, Goldberg A, Hall T, Riggins CW, Rister RS, eds. The complete German Commission E monographs: therapeutic guide to herbal medicines. Austin, TX: American Botanical Council, 1998.
- WHO. Echinacea. In: WHO monographs on selected medicinal plants. Geneva: World Health Organization, 1999: 125–44
