Similarities. Both the AI and RDA are to be used as a goal for individual intake. In general, the values are intended to cover the needs of nearly all persons in a life stage group. (For infants, the AI is the mean intake when consuming human milk by infants in the age group. Larger infants may have higher needs, which they meet by consuming more milk.) As with the RDAs, AIs for children and adolescents may be extrapolated from adult values if no other usable data are available.
Differences. There is much less certainty about the AI value than about the RDA value. Because AIs depend on a greater degree of judgment than is applied in estimating the EAR and subsequently an RDA, the AI may deviate significantly from the RDA, if it could have been determined, and may be numerically higher than the RDA, if it were known. For this reason, AIs must be used with greater care than is the case for RDAs. Also, the RDA is always calculated from the EAR, using a formula that takes into account the expected variation in the requirement for the nutrient (see previous section).
The Tolerable Upper Intake Level (UL) is the highest level of daily nutrient intake that is likely to pose no risks of adverse health effects in almost all individuals in the specified life stage group. As intake increases above the UL, the risk of adverse effects increases. It is based on an evaluation conducted using the methodology for risk assessment of nutrients described in Chapter 3 of this report. The need for setting ULs grew out of the increased fortification of foods with nutrients and the use of dietary supplements by more people and in larger doses.
The term tolerable intake was chosen to avoid implying a possible beneficial effect. Instead, the term connotes a level of intake that can, with high probability, be tolerated biologically. The UL is not intended to be a recommended level of intake, and there is no established benefit for healthy individuals if they consume a nutrient in amounts above the recommended intake (RDA or AI). As in the case of applying AIs, professionals should avoid very rigid use of ULs and first assess the characteristics of the individuals and/or group of concern; for example, source of nutrient, physiological state of the individual, length of sustained high intakes, etc.
For some nutrients there may be insufficient data on which to