Adverse Effects of Dietary Supplements

The FDA has the burden of proving that a dietary supplement is adulterated, that it "presents a significant or unreasonable risk of illness or injury." The FDA, however, must rely on the honesty of the industry to ensure safety. Through scientific studies, dietary supplement manufacturers determine that their ingredients present no significant or unreasonable risk to consumers and submit that information to the FDA. Although the FDA does not participate in or oversee the testing of dietary supplements for safety, the FDA is responsible for removing unsafe dietary supplements from the market.
Adverse or suspected adverse effects of dietary supplements should be reported to the FDA. Once the FDA receives such information, it generates alerts and warnings for consumers and letters notifying the manufacturer that their dietary supplement may be associated with harmful adverse events. The results of these actions may range from a consumer warning, labeling change, or product recall to a full-fledged product withdrawal. Dietary supplement manufacturers may voluntarily recall a product, as in the case of a labeling error, product mix-up, contamination, or questionable stability of the product or its components. The FDA may also request or order a product recall based on the above criteria.
Product recalls are expensive and done because there is something wrong with the product. The type of recall for dietary supplements depends on the severity of potential adverse effects. A class I recall means there is reasonable evidence to suggest that use of a product will cause serious adverse effects or death; a class II recall means a product may cause temporary or treatable adverse effects or that the risk of serious adverse effects is low; and a class III recall means the adverse effects are not likely to be serious.
Below is an adaptation of a letter from the FDA's Office of Nutritional Products, Labeling, and Dietary Supplements to the distributor of a hazardous dietary supplement.