FIGURE 3-4 Illustration of the population at risk from excessive nutrient intakes. The fraction of the population consistently consuming a nutrient at intake levels in excess of the UL is potentially at risk of adverse health effects. See text for a discussion of additional factors necessary to judge the significance of the risk. LOAEL = lowest-observed-adverse-effect level; NOAEL = no-observed-adverse-effect level; UL = Tolerable Upper Intake Level.

to reduce risk. Few precedents for nutrients are available for such policy choices, although in the area of food additive or pesticide regulation, federal regulatory agencies have generally sought to ensure that the ninetieth or ninety-fifth percentile intakes fall below the UL (or its approximate equivalent measure of risk). If this goal is achieved, the fraction of the population remaining above the UL is likely to experience intakes only slightly greater than the UL and is likely to be at little or no risk.

For risk management decisions, it is useful to evaluate the public health significance of the risk, and information contained in the risk characterization is critical for that purpose.

Thus, the significance of the risk to a population consuming a nutrient in excess of the UL is determined by the following:

1. the fraction of the population consistently consuming the nutrient at intake levels in excess of the UL,

2. the seriousness of the adverse effects associated with the nutrient,

3. the extent to which the effect is reversible when intakes are reduced to levels less than the UL, and