Recent media reports seem to have strengthened the case for using echinacea to ward off or treat the common cold. But, are they based on valid new evidence?
The LATimes [item no longer available by link] for instance, says researchers carried out an “analysis of 1,600 patients pooled from 14 previously published studies found that echinacea reduced the chances of catching a cold by 58% and shaved 1.4 days off the duration of a cold.”
The researchers who carried out this analysis point out that none of the previous trials was large enough to be valid, but somehow they attempt to give them new credence by mixing together the data from lots more dubious studies. One bad apple can almost certainly spoil the barrel, but throw together a couple of dozen bad apples and that barrel is going to be humming before the day is out, surely?
Meta analyses of solid double-blind, placebo-controlled clinical trials certainly can shed new light on old findings, but what they do not do is create new data points, they are simply a re-analysis of old results pooled.
Craig Coleman of the University of Connecticut whose team carried out the meta analysis, point out that none of the trials analysed individually were big enough to reveal the benefits of Echinacea. Somehow his new analysis of old data demonstrates an almost two-thirds reduction in the risk of catching a cold compared to a person not using Echinacea. But, how could that be, if those earlier trials succumbed to serious wishful thinking and the placebo effect, then the whole argument is in doubt.
Wallace Sampson, an emeritus adjunct professor of medicine at Stanford University School of Medicine is quoted as saying that because the methodologies of some of the earlier studies are so suspect, this casts doubts on the pooled result. Exactly.
The team also reports that of 800 products containing Echinacea they investigated, there are large variations in the quality, which part of the plant was used – flower, stem or root – and how much so-called active ingredient is present. In addition, they suggest that more work is needed to check the safety of the countless formulations available. Their warning echoes other studies that have pointed to toxicity problems associated with long-term use of Echinacea products, although admittedly some of those studies might also be considered invalid because of poor methodology.
So, should we run to our local herbalist on the off-chance that we might catch a cold or if you’ve already caught one quickly down a dose of Echinacea to “shave off” 1.4 days or runny noses and sneezing? I don’t think so, not unless you don’t mind putting up with a whole lot of bad apples.