Review of the information does not need to prove toxicity, only that there is an unreasonable risk of its occurrence (see Box 3-2). Such an analysis is captured in the monograph. The evaluation of the totality of the scientific evidence is thus summarized in conclusions about risk based on the high level of concern resulting from the in-depth review and analysis of the available information.
To guide those making conclusions about risk as a result of the integrative evaluation component, it might be possible to develop a taxonomy of levels of risk—such as “no basis for concern,” “some grounds for further monitoring,” “some basis for concern about risk,” or “presents a risk that warrants regulation under the FDCA as amended by DSHEA.” This was not done in this report because the definitions might become too prescriptive given the variety of information and types of dietary supplement ingre-
It has been said that the “… dose differentiates a poison from a remedy.” Even essential substances for humans, such as oxygen and water, can be toxic in high concentration or if imbibed in large amounts. Thus no substance is completely “safe.” Safety is a qualitative term that is applied to a variety of situations or environmental factors and is related to the context in which it is evaluated. What is safe in one situation (e.g., driving 50 mph) might be considered unsafe in another. In relation to ingested substances, in some cases it is possible that concerns related to adverse effects resulting from consumption may be mitigated by benefits derived from the substance when ingested.
For drugs and medical devices, safety is evaluated as a measure of potential harm relative to benefit (see Chapter 1). For food additives, safety is defined as the reasonable certainty of no harm, without consideration of benefit beyond that of improving the functional characteristics of the resulting food product, such as retarding microbial growth or maintaining texture. The DSHEA classifies dietary supplements similarly to food, and therefore supplements are considered, like conventional foods, to be reasonably safe.
While dietary supplements are biologically active substances that may have desirable health benefits, they may also cause adverse health outcomes. DSHEA requires that the FDA determine that a dietary supplement ingredient is unsafe (i.e., consumption results in unreasonable risk of illness or injury at recommended intake levels) rather than requiring that a manufacturer provide data supporting its safety, as it does for food additives, drugs, and medical devices.
Since FDA’s authority is limited to evaluating a dietary supplement ingredient for potential to cause illness or injury, but it cannot take into account possible beneficial effects on health, any safety framework for a dietary supplement ingredient must depend on (1) the accumulation of evidence indicating potential for harm and (2) the determination of when this accumulated evidence raises concern to a point that a significant or unreasonable risk exists.