We've lost count of the number of studies on echinacea, the popular herbal remedy that many people take for colds. And now another one is hitting the headline - this time the verdict is that it's not effective against colds, and that taking it isn't worthwhile.
Published in the journal Annals of Internal Medicine, the study was carried out by researchers at the American College of Physicians. They studied 719 people with early cold symptoms and gave them either nothing at all, a pill containing echinacea or a dummy pill (placebo).
The result was that the volunteers who took echinacea didn't have any less severe symptoms but that they did have slightly shorter colds - but only three hours shorter, which the researchers deemed statistically insignificant.
Well that's that, you might think. But some earlier studies have suggested otherwise. A 2007 study, published in The Lancet, for instance, supported the use of echinacea as a means of shortening the amount of time you have a cold.
And there have been countless others, many of which say there's something in echinacea's reputation as a cold defence herb, and many that say taking it is a waste of time. In the future we expect even more studies will do the same.
So if there's all this doubt about whether or not echinacea works, why are people still buying it? While the plant may or may not have immune-boosting properties, perhaps it has something to do with the fact that people believe it could help them.
Studies show that having a positive attitude may protect against many illnesses, including colds, so if echinacea helps you believe you're doing something to help yourself, isn't that a good thing?
Will you be taking echinacea this winter? Or do you think it's a waste of money?