Herbal placebo?

While some traditional herbal medicines (foxglove, opium, willow, qinghaosu) turn out to actually work when studied carefully, others don’t. The most likely explanation for the reported benefits in some ineffective herbal products is some sort of placebo effect. That’s become more likely following recent research that tested 44 herbal products on sale in the USA and found that a third of them were completely missing the active ingredient, with some of the others containing inactive fillers such as oats or potentially active (or allergenic) plants other than those on the label.

The researchers used DNA barcodes: measurements of short DNA regions that are variable enough to distinguish most plant species, they didn’t measure the putatively active compounds in the herbs.  The DNA approach is much more efficient, but it can give an unrealistically favorable view of the situation: it’s possible that even where the right plant was present, it didn’t have a meaningful concentration of the right compounds.

There was a bit of publicity over this when it came out a few weeks ago (I wrote about it on my blog), but now the New York Times has picked the story up and has a lot more detail.