quate for the specified criterion, given current knowledge. When an individual's intake is less than the RDA, the risk of an inadequate intake is present. The risk increases as the intake falls further below the RDA. At 2 standard deviations (SD) below the EAR, it would be nearly certain that the individual's requirements would not be met (NRC, 1986). Neither reported dietary intake nor any other single criterion can be used, by itself, to evaluate the nutritional status of individuals. A usual intake that is well below the RDA may be an indication of the need for further assessment of nutritional status by biochemical tests or clinical examination.
An AI is based on observed or experimentally determined approximations of the average nutrient intake, by a defined population or subgroup, that appears to be sufficient to sustain a defined nutritional state in the specified population. It is emphasized that, in contrast to the EAR, which is an estimate of the requirement that applies to individuals, the AI is usually derived from mean intakes of groups —the group rather than the individual is the unit of observation. The AI is therefore higher than the EAR would be, if it could be determined, since by definition, the EAR is the intake that meets the nutrient need of only 50 percent of the individuals in a group. Because of uncertainties about the relationship of the AI to the actual average requirement, the AI provides an imprecise basis for the assessment of nutrient intakes of population groups. Thus, the applications of the AI must be quite different from those of the EAR. However, healthy individuals with an intake at or above the AI are assumed to have a low risk of intake inadequate for a defined state of nutrition.
The UL is the highest level of daily nutrient intake that is likely to pose no risk of adverse health effects to almost all individuals in the general population. As intake increases above the UL, the risk of adverse effects increases. In most cases it applies to usual intakes from all sources, but in the case of magnesium, it does not apply to intake from food or local water supplies.
Similar to the situation for nutrient requirements, the intake at which a given individual will develop adverse effects as a result of taking high amounts of a nutrient from food and/or nonfood sources cannot be known with certainty. If the individual's intake is