FDA is finding an alarming number of OTC supplements are adulterated. Chemicals and drugs have been deliberately placed into them in violation of the law and without any warning on the label. It is unclear whether this practice has yet caused any serious medical problems or deaths but the potential for such is huge.
Why would manufacturers deliberately adulterate their own products?
Generally either to make them "work" better and therefore sell better; or to save money (it's cheaper to spray alfalfa with a drug and call it something exotic than it is to grow the actual exotic plant itself). Examples of this are
How is this "allowed" to continue?
It isn't; the FDA is very busy these days screening supplements, banning those found to be adulterated and in some cases, prosecuting individuals responsible. The problem is that there are a vast number of different products sold over the counter and online, and screening each one for possible adulteration is expensive and time-consuming.
Beware These Kinds of Supplements
In my view, at the moment (late March, 2011), people should not take OTC supplements claiming to help any of the following conditions:
Supply Chain Issues
Manufacturers often do not know that their own products are adulterated because they generally do not test each ingredient in a supplement for such adulteration and because many of the ingredients that they purchase to produce their products are imported from other countries; countries that often have very lax or no food and drug laws. The image of a company carefully growing and tending its own herbs and ingredients is a fantasy. Like all manufactured products, OTC supplements are made from raw materials that are usually purchased on the basis of price.