Problems and Prospects: Public Health Regulation of Dietary Supplements.

Dietary supplements are a global business worth more than US$100 billion annually. These supplements are taken by up to 50% of adults and perhaps one-third of children in economically advanced economies. Definitions of dietary supplements differ from country to country, and regulation is generally lax and often seems to be directed more toward promoting commerce than protecting public health. Supplements may directly cause toxic reactions or may interact with other supplements or pharmaceuticals. Some supplements are found to have been contaminated with heavy metals, and others do not contain the expected quantities of active ingredients. In general, supplements are not needed except in cases of established deficiencies, and excess of some nutrients can increase cancer rates. There are important public health reasons for taking some supplements, including folate and iodine in pregnancy. This review discusses the public health concerns associated with dietary supplements and suggests directions for further regulation.