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DRI Dietary Reference Intakes Calcium Vitamin D
serum 25OHD levels, these signals can be taken into account. Focusing exclusively on vitamin D acute toxicity for the purposes of establishing a UL and ignoring the emerging data related to other adverse events is not in the best interests of public health.
Selection of Indicator for the UL: Vitamin D
The best available data set for establishing a UL for vitamin D is associated with the onset of hypercalcemia and related toxicity. This indicator is selected as the basis for the UL for all age groups except infants, with the caveat that while it serves as a starting point, it is to be subject to adjustment for uncertainty. The adjustment is based on: (1) the recognition of the goal of public health protection, which suggests that avoiding hypervitaminosis D is, of course, desirable, but not necessarily sufficient; and (2) the emerging data concerning other adverse effects at intakes lower than those associated with acute toxicity and at serum 25OHD levels previously considered to be at the high end of physiological values. Taken as a whole, the body of evidence suggests that there is reason to proceed cautiously in assuming that higher levels of vitamin D intake below those expected to cause hypervitaminosis D are harmless, especially in the absence of data to demonstrate benefit at such intake levels. For infants, the long-standing measures related to retarded linear growth serve as the indicator for the UL.
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 as described further below for specific life stage groups.
VITAMIN D UPPER LEVELS: INTAKE-RESPONSE ASSESSMENT AND SPECIFICATION OF UPPER LEVELS
The ULs established for vitamin D are shown in Table 6-4 by life stage group. The ULs for infants are discussed first. This is followed by a discussion of ULs for adults rather than children and adolescents because the UL for adults is used to extrapolate or scale a UL value for children and adolescents. A discussion of ULs during pregnancy and lactation follows.