research addressing unanswered questions relative to some of the signals detected.

In outlining the task, FDA requested that the Framework include a method based on safety concerns to categorize and prioritize dietary supplement ingredients sold in the United States. Given the variety of types of information that are likely to be available, the Framework classifies scientific information into four broad categories for use in determining the potential for serious harm for a specific dietary supplement ingredient. These categories of data include:

• Human data,

• Animal studies,

• In vitro experiments, and

• Information on related substances.

Subsequent chapters describe the types of information that may be available in each category of data and the strengths and weaknesses of these different data sources in evaluating the potential of a dietary supplement ingredient to cause harm (Chapters 4 through 7). Also described are how to consider the potential for dietary supplement interactions with drugs and other xenobiotics⁷ (Chapter 8), important considerations that should be factored into evaluations when vulnerable populations consume dietary supplements or when supplements are widely consumed (Chapter 9), and considerations for integrating the available data from various sources to determine an overall level of concern (Chapter 10) using a causal model diagram. The level of concern appropriate for a specific piece of information within a particular data category (i.e., human, animal, in vitro, or related substances information) is summarized in diagrams that relate the available evidence to show the level of concern when consuming a dietary supplement ingredient.

Evidence that results in a higher level of concern indicates a more immediate priority for further investigation to determine if an unreasonable risk to public health exists. In contrast, a single piece of information resulting in a lower level of concern may suggest that continued routine monitoring for new evidence is warranted—evidence that might elevate the level of concern and thus its priority for increased scrutiny.