Although each chapter strives to describe all types of information that may be available, it is important to recognize that for most dietary supplement ingredients, it will be difficult, if not impossible, to find useful information from all data categories. The following section provides an overview of the types of information that may be encountered and summarizes general scientific guidelines for assessing the relevance and quality of the available information from each data category (Box 3-3). More specific information and details are provided in Chapters 4 through 9.

As briefly outlined in the process description earlier in this chapter, included in the Framework is a qualitative method to evaluate the nature of the evidence for a specific piece of information within a particular data category (i.e., human, animal, in vitro, or information about related substances). Distinguishing characteristics of evidence determine where a piece of information falls on the continuum of lower to higher level of concern. This is summarized in diagrams referred to as spectra of concern. Evidence that results in a higher level of concern indicates a more immediate priority for investigating further whether an unreasonable risk to public health exists, because a higher level of concern suggests a potential risk to public health. In contrast, a single piece of information resulting in a lower level of concern may suggest continued routine monitoring for new evidence that might elevate the level of concern and thus initiate increased scrutiny.

Information about human use of dietary supplement ingredients may be in the form of formal studies, such as clinical studies or trials and epidemiological studies; in the form of spontaneously reported adverse event reports or literature case reports; or in the form of information about historical use of the ingredient. Because there is no requirement that dietary supplement ingredients undergo formal studies prior to marketing, formal study data on a dietary supplement ingredient will be less commonly available than spontaneous adverse event reports and information about historical use. The lack of such data, however, does not diminish their importance.

Data about human intake can be useful either as indicators of possible risk or, conversely, as mitigators of concerns raised by other categories of data. Within each type of human data, questions can be asked about the nature and quality of the scientific information to determine whether the information raises the level of concern regarding the probability to cause harm. While discussed in detail in Chapter 4, the general spectra of concern