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Dietary Supplements: A Framework for Evaluating Safety
A FORMULAIC APPROACH FOR INTEGRATING DATA IS NOT PRACTICAL
Under the current legal and regulatory framework, the safety of many dietary supplement ingredients is more difficult to evaluate than other substances because of a general lack of quality data in the public domain, as well as the lack of requirement for premarket safety evaluation to drive future safety studies.1 In the absence of scientific studies specifically designed to assess the safety of dietary supplement ingredients, it is not possible to apply a specific algorithmic or formulaic approach to determining safety, and expert2 judgment in the interpretation of data is likely to be important, as it is for other substances. The Framework outlined in this report is different than frameworks that have formulaic components or that rely largely on assumptions that apply to the particular type of product being evaluated (see Appendix A). For example, the Flavor and Extract Manufacturers Association process relies largely on the fact that flavors will not be ingested in large amounts, and the Cosmetic Ingredient Review is unique in that many of the ingredients it evaluates are not bioavailable. The framework for Dietary Reference Intakes of the Institute of Medicine’s (IOM’s) Food and Nutrition Board includes a model for determining tolerable upper intake levels for ingestion of vitamins and minerals (IOM, 1998). The model is based on applying an uncertainty factor to the level at which no adverse events are observed from consumption of a nutrient, or if no data are available, to the lowest level of chronic intake at which adverse events are observed.
It is also not appropriate to develop a hierarchical approach to considering the different types of data—human data, animal data, in vitro data, or information about related substances—for various reasons. In part, such an approach is not feasible because of limitations in the quality of the data and what different types of studies can reveal, but these limitations can be overcome with other types of data. Although a hierarchical approach is not practical, it is possible to weigh the various types of data available to make conclusions regarding risk to human health. The second part of this chapter provides guidance on comparing animal and human studies with seemingly inconsistent results, but each situation will need to be evaluated to weigh the data appropriately.
Exceptions to this include some nutrients and dietary supplements that have been evaluated for specific medicinal use as drugs (e.g., niacin and melatonin).
Note that “expert” could describe a number of different types of experts, with several persons providing different viewpoints, including a perspective on the historical use of the substance.