Echinacea: Maybe this Herbal Remedy Works After All
For about a decade now, I’ve cringed whenever I’ve seen someone selling or buying echinacea. The echinacea flower is awfully pretty, curing a boring yard of a case of the summer doldrums. But a series of three studies published in top-of-the-line medical journals in 2005 — Journal of the American Medical Association, New England Journal of Medicine, Annals of Internal Medicine — appeared to show that echinacea does not prevent the common cold, as herbalists have long claimed it does.
However, it has recently come to my attention that a meta-analysis of studies using the stringent standards of a Cochrane Review has been published in JAMA. This “meta-analysis” is valuable because it pools together the results of many studies, rather than relying on just one, which allows for greater predictive power based on a large number of cases. The additional approach of a Cochrane Review — in a nutshell, to only include the results of studies meeting the highest methodological standards — further strengthens the confidence of the results of the meta-analysis.
Here’s the bottom line: when results from the best studies are pooled together, it turns out that of people taking echinacea regularly, 42.8% develop a cold. Of people who do take echinacea regularly, 55.7% develop a cold.
There are limitations to these findings:
- First, clearly, taking echinacea is not a guarantee of health; it seems to just lower the risk of contracting a cold to a mild degree.
- Second, the authors of the meta-analysis note that there is wide variation in what parts of the plant were used in these studies, in what variety of the echinacea plant was harvested, and in what method was used to turn the flower into a medicine.
- Third, the authors note that some “publication bias” is possible. That is, positive results are more likely to be published than negative results, because as fallible human beings journal editors find positive results to be more appealing and newsworthy. This means that, you guessed it, further research is needed, most likely a single large study with a large number of participants, the results of which are committed to be published before the direction of the results in known.
- Finally, unless you harvest your own, you can’t be sure what you have is really echinacea. Consumer Reports investigated echinacea sellers a decade ago and found that a number of “echinacea” products being sold on the market had little to no actual echinacea in them, and that some of what they bought was contaminated with toxic lead.
With all these limitations acknowledged, however, it’s important to acknowledge that the weight of evidence has shifted in favor of echinacea’s at-least-mild efficacy. Given the relative harmlessness of echinacea to the human body (unless your products are contaminated with lead), it might not be a bad idea to take the stuff to stave off the sniffles.
Science is not about coming up with a single infallible result that applies for ever and ever. It is the opposite: a commitment to careful procedure, to ferreting out possible sources of bias, to questioning the basis for conclusions. Science must be comfortable with doubt, to accept that as bias is rooted out and evidence becomes more clear, we just might have to change our minds.