A study in the Journal of Agricultural & Food Chemistry suggests that one reason might be related to the lack of manufacturing standards in the production of this product, which leads to significant variability in the contents of different brands.
Among 11 brands tested, 3 contained an Asian adulterant (Asian Actaea) instead of black cohosh, and 1 contained both genuine black cohosh and the adulterant. For the products containing only black cohosh, there was significant product-to-product variability.
The bottom line?
There are 18 species of Asian Acetaea. Adulteration of black cohosh products with the less costly Chinese Actaea species has be recognized by the American herb industry for more than a decade. For example, in 2005 the AHPA added the Asian Actaea species to its list of potential botanical adulterants.
7/16/06 10:17 JR; Updated 6/18/15 JR