Echinacea, currently one of the most popular herbal remedies in Europe, which is taken to treat the common cold, had no effect when tested on a small group of students with colds, report researchers in the US.
Researchers at the University of Wisconsin in Madison, US, assessed the efficacy of dried, encapsulated, whole-plant echinacea as early treatment for the common cold, on a group of 150 students with recently started common colds.
In a randomised, double-blind trial, the team gave half the group an encapsulated mixture of unrefined Echinacea purpurea herb (25 per cent), root (25 per cent) and E. angustifolia root (50 per cent) taken in 1g doses six times on the first day of illness and three times on each subsequent day of illness for a maximum of 10 days. The other half received a placebo.
Published in the latest issue of the Annals of Internal Medicine, the study authors concluded: "No statistically significant differences were detected between the echinacea and placebo groups for any of the measured outcomes."
They report that severity of symptoms over time were nearly identical in the two groups. The cold lasted on average 6.01 days in both groups (5.75 days in the placebo group, and 6.27 days in the echinacea group). After controlling for severity and duration of symptoms before study entry, sex, date of enrollment, and use of nonprotocol medications, researchers found no statistically significant treatment effect.
They concluded that unrefined echinacea provided no detectable benefit, or harm, in the study participants. Previous studies have however shown positive effect from the herb - this may be due to a huge variation of different blends and concentrations available on the market. Some estimate that there are around 200 different forms, from teas to capsules, sold worldwide, but very few have been tested.
The plant chemicals also vary among botanical species, growing conditions, plant part and extraction method, said the team, making it possible that one preparation could be beneficial and another have no effect.
The team is calling for more research on echinacea's immune-boosting potential. Meanwhile companies marketing the herb will have to work even harder to provide the science backing their product.
Echinacea flowers blossom throughout North American plains and were originally used to treat a variety of ailments by Native Americans.