Nov 08 2018

Echinacea Does Not Work for the Cold

We are heading into cold and flu season, so Time magazine decided to helpfully tell us what the science says about echinacea and the common cold. Unfortunately, they completely bungled their report, getting the bottom line wrong. Exactly where they go wrong, however, is extremely common and instructive.

The terrible article is partly not the fault of the author. They spoke to experts and tried to do a balanced piece. Unfortunately, there are experts out there who are biased and just wrong. The author was not able to make sense of the evidence themselves, and so they helplessly just passed along whatever nonsense they were told. This is another manifestation of the infiltration of “alternative” medicine into our system – there are always going to be “experts” out there who are just alternative cranks, but they will get quoted along side more serious scientists.

For example, they write:

Other experts say there is evidence that echinacea can be helpful. “Echinacea is popular because it does work for at least some people,” says Kelly Kindscher, a professor of environmental studies at the University of Kansas who has written a textbook on echinacea. While some clinical trials have not shown echinacea to be effective, Kindscher says others have found benefits.

I understand listening to someone who wrote a textbook on the topic, but this conclusion flies in the face of published reviews. The next statement shows where they go wrong:

A 2010 study published in the Annals of Internal Medicine compared echinacea to a placebo and to no treatment at all. It found evidence that echinacea outperformed both when it came to reducing the duration of the common cold — but these benefits were too small to be considered statistically significant.

You see, when the results are not statistically significant, that means the treatment did not work. This is a negative study, but the author is portraying a
“trend” as if it means something. This is hopelessly naive, as there is often a trend based entirely on researcher bias or less than completely rigorous study design. Even when the results are statistically significant that may not be enough – we need to see a dose response, and a clinically significant result with reasonable effect sizes. Further, this needs to reliably replicate.

It gets worse as the author quotes experts from herbalism-loving Germany, and departments of alternative nonsense. They essentially say that while the evidence is not technically positive, there is a persistent trend to some effect, so why not give it a try?

But they, and by extension the author, are asking the wrong question. The real question is – when we look at the entire scientific literature relevant to the question of whether or not echinacea is effective for the cold or flu symptoms or prevention, what conclusion is the pattern of total evidence consistent with? The answer is, the evidence is strongly consistent with the conclusion that echinacea is of zero benefit, there is no effect there.

The Evidence

Here are what published reviews of the evidence show. A 2014 review of echinacea simply concluded there was no statistically significant difference from placebo, and therefore echinacea is of “no benefit.”

A 2014 Cochrane systematic review concluded:

Echinacea products have not here been shown to provide benefits for treating colds, although, it is possible there is a weak benefit from some Echinacea products: the results of individual prophylaxis trials consistently show positive (if non-significant) trends, although potential effects are of questionable clinical relevance.

Translation – it doesn’t work. The Cochrane reviews are methodologically extremely rigorous, but they are the epitome of evidence-based medicine, including its serious limitations. You often end up with ridiculous conclusions like this one, thinking that non-significant trends are anything but bias and noise. But also don’t miss the last statement – “questionable clinical relevance” means that effect sizes were tiny. This not only means that echinacea is not useful, even if the small effects were real, it also means the effects are so small they are probably not real.

That is a point often missed by biased or naive reviewers. Tiny effect sizes are more likely to be due to bias or sloppy methods. They are essentially down in the noise, and they do call into question the reality of the effect itself.

So just looking at the clinical evidence, there is no clear effect at all, and even the most generous interpretation is that there may be a clinically insignificant effect. This makes the bottom line simple – don’t waste your money on echinacea.

But a science-based approach takes a look at more than just the direct clinical evidence (although the clinical evidence is the most important). One might ask, for example, why anyone thought echinacea would be effective in the first place. The history of echinacea actually does not go back that far. In the 1800s it was used by Native Americans for a host of ailments:

Information about the use of the plant from traditional healers ranges from external application for wounds, burns and insect bites to the chewing of roots for toothache and throat infections, and internal application for pain, coughs, stomach cramps and snake bites.

It was then picked up by a good old-fashioned snake oil salesman, H.C.F. Meyer, who sold a concoction of echinacea as Meyers Blood Purifier. He leveraged the Native American connection for marketing purposes. From there the herb took on a life of its own. But there was never any history to even suggest a traditional use (not that this would mean much anyway) to support an effect for the common cold.

It is also worth pointing out that purchasing an echinacea product is a crapshoot. Multiple studies show the poor regulation of the industry. A 2018 study, for example, found:

All of the tested herbal products showed considerable discrepancies between ingredients listed on the label and the ones detected using DNA metabarcoding, registering an overall ingredient fidelity of only 43%.

So your chance of getting what’s on the label is less than half. In addition, other studies show that commonly purchased herbal supplements contained contaminants 20% of the time.

So here is the bottom line that Time magazine should have told its readers – Echinacea is marketed for cold and flu symptoms, but there was never any reason to suspect that it worked. Hundreds of studies have failed to show any significant benefit, either statistically or clinically, which means it basically does not work. Further, the industry is so poorly regulated you can never know what you are actually getting. It’s basically a con – don’t fall for it.


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