Potential risks associated with the use of herbal anti-obesity products.

The public wants an easy way to control obesity. Herbal anti-obesity products attract users because of their health claims, assumed safety, easy availability and extensive marketing. These products can be very heterogeneous in nature and have unpredictable levels of active ingredients, and unpredictable and potentially harmful effects. They may contain highly toxic herbs (e.g. Aristolochia species), potent herbs not recommended for use in weight control (e.g. Ephedra sinica) and herbal laxatives with potential hepatotoxic and nephrotoxic effects (e.g. anthraquinones). However, the presence of such herbs may not be disclosed on the product label. They may contain adulterants (e.g. drugs, drug analogues and thyroid extracts), including drugs that have been withdrawn from the market (e.g. fenfluramine). For all these reasons, herbal anti-obesity products can cause direct toxicity or adverse interactions with concurrent medications. Physicians and other healthcare professionals need to be aware of the problem. They should warn their patients about the heterogeneous nature of these agents and the potential risks associated with their use. They should report suspected adverse reactions to their national spontaneous reporting system.