There's been an ongoing battle over the value of herbal supplements. Experts weighing in on both sides as to whether they help, do nothing, or actually hurt. You can't tell from the people taking them because of the extremely powerful placebo effect, researchers are finding has a much bigger effect than they thought possible.
Researchers in Canada, rather than get into that fray, decided to see if the popular supplements were what the label claims. They bought samples in the US and Canada of the 12 most popular supplements. Only 2 were exactly what the label said, 10 were adulterated or contained none of what the label claimed, and two contained Black Walnuts as one of the fillers. That could be dangerous to a nut allergy sufferer.
I can't find the original site where the chart came from but many sites talk about the study.
This one presents both side of the fuss.