for concern at serum 25OHD levels above 125 nmol/L (50 ng/mL). Given the concern about high serum 25OHD levels as well as the desirability of avoiding mis-classification of vitamin D deficiency, there is a critical public health and clinical practice need for consensus cut-points for serum 25OHD. The current lack of evidence-based consensus guidelines is problematic and of concern because individuals with levels of 25OHD serum above 50 nmol/L (20 ng/mL) may at times be diagnosed as deficient and treated with high-dose supplements of vitamin D containing many times the levels of intake outlined in this report.
Although this report identifies upper levels of intake below which adverse effects are not expected to arise, ULs are intended to serve as a lifetime public health measure for a free-living, unmonitored population. Those responsible for determining the appropriate dosages of nutrients to be studied in carefully controlled experimental trials conducted with appropriate adverse event and safety monitoring have the opportunity to bring other considerations into play when deciding on the levels of nutrients that are acceptable and appropriate for subjects taking part and being monitored in such studies. Research using intakes higher than those specified in the ULs can be justified under a number of circumstances after careful review of the literature and through the use of appropriate study protocols. Indeed, such studies are likely to be informative to the understanding of dose–response relationships and the health benefits or risks associated with calcium and vitamin D intakes.
As described in Chapter 1, the DRI development process has recently been subjected to a review as well as targeted discussions about the process and ways to enhance it (IOM, 2008). As an overall result of these discussions, DRI development is now placed more clearly in the context of the risk assessment approach—that is, an organizing framework for conducting evaluations with public health implications often made with evidentiary uncertainties. There is also a series of existing “gap issues”—specifically, needed methodologies and guidelines—that have been identified as important to improving and enhancing the process for developing DRIs and would benefit from targeted efforts to resolve the gaps (Taylor, 2008).
The report of this committee is the first DRI report to be completed subsequent to the 2004 to 2008 evaluation of the DRI development process. It has been structured to be consistent with the risk assessment pro-