As we have previously noted (go here, for instance), dietary supplements are like drugs–that is, they are claimed to treat or prevent disease and have a physiological effect on the human body. And they are marketed like drugs–that is, they are marketed for their claimed beneficial physiological effects on the human body.
But because they are made from "natural" substances, they are not regulated as drugs. The most imporant loophole is that the manufacturer doesn't have to show that a dietary supplement is safe and effective for its intended use before it can be mass marketed (as is generally the case for a drug). So, it is useful for consumers to remember that dietary supplements can be harmful and that they can't rely on the government for protection from those harms.
This article by Dr. Janani Rangaswam provides some consumer-protection information. Here's an excerpt:
I recently cared for a patient with worsening kidney failure. After a full investigation, I could find no cause but a coincidence that he had used "Kangaroo," a sex-enhancing supplement, around the time he got sick. While there is no way to prove or disprove the link between the pill and the ailment, it made me consider how little we know about the toxicity of supplements despite how common they are, and the significant number of deaths and life-threatening events they cause each year. Americans today spend about $30 billion directly on supplements such as vitamins, minerals, amino acids, and herbal remedies. The Food and Drug Administration received more than 6,000 adverse-event reports involving supplements from 2008 to 2011, with about 2 to 3 percent linked to deaths. In the same period, poison control centers nationally received 145,000 supplements-related queries, of which about 4,800 were believed to be major adverse events.
