That products (in this case herbal supplements, as discussed in this article) are not as they seem is only a problem if one takes seriously the value of and need for such products. Evidence supported by quality peer-reviewed science as to the value of such supplements is sorely lacking.
A decent balanced diet emphasizing variety of food and moderate quantities is more than sufficient to meet nutritional needs. To avoid adulterated supplements, it is most effective to avoid supplements, and be healthier and a bit wealthier in the process. The money saved can be put to much better use.