The risk assessment framework, as described in Chapter 1, specifies that, in the case of ULs, the available data pertaining to adverse effects be first examined for evidence of a benchmark intake (BI). Alternatively, either a no observed adverse effect level (NOAEL) or a lowest observed adverse effect level (LOAEL) is considered. In the case of calcium, limited new information has become available since 1997. The indicators selected are calcium excretion for younger age groups, and kidney stone formation for older age groups. The calcium excretion data provide information for a group for which no data were available in 1997. The newer data on kidney stone formation form a basis for a UL that is more akin to conditions experienced by the normal, healthy population than is calcium-alkali syndrome, although the cautions expressed by Patel and Goldfarb (2010) concerning the vulnerability of older persons to calcium-alkali syndrome with the use of calcium supplements are worthy of note.
The available data could not offer a BI or be used to estimate a dose–response relationship. The basis for the ULs is a NOAEL for infants and a LOAEL for adults, as described further below for specific life stage groups.
The ULs for calcium established for the DRI life stage groups are shown in Table 6-2. These values suggest that the levels of intake regarded as consistent with a UL are relatively close to the levels of intake considered to be appropriate for nutritional adequacy.
In the previous 1997 DRI report (IOM, 1997), a UL for calcium for infants was not specified owing to lack of data. The 1997 report noted a small, randomized trial of 81 infants (103 at baseline, ages 2.5 to 5.0 months at entry) designed to examine the tolerance of calcium-supplemented infant formula through 9 months of age (Dalton et al., 1997). The data, as analyzed in 1997 (IOM, 1997), indicated only that infants fed calcium at up to approximately 1,750 mg/day experienced no adverse effect on iron status.