Setting Dietary Reference Intakes with the use of bioavailability data: calcium.

The determination of Dietary Reference Intakes (DRIs) for calcium, especially in children, has relied in significant part on the evaluation of the relation between calcium intake and calcium absorption and retention. At present, most of these studies are conducted with the use of dual-tracer stable isotope, although mass balance or other isotope methods are still used occasionally. Studies carried out to evaluate DRI values need to be conducted under the most controlled conditions possible. However, the achievement of such conditions can be difficult, especially in studies in small children, because strict, long-term dietary monitoring and sample collections are not well tolerated. Other dietary factors, which include vitamin D status and the presence of enhancers and inhibitors of calcium absorption, may have to be considered. However, for most healthy populations who do not have very low calcium intakes or serum 25-hydroxyvitamin D concentrations, other dietary factors will not be major determinants of the net calcium absorption or retention that will be used for the establishment of DRI values. Ultimately, DRI values must be chosen based on an attempt to achieve some targeted value for calcium absorption/retention or to maximize, within constraints, the overall calcium absorbed and retained. In children, it is important to use data obtained at the age and pubertal status being evaluated rather than to interpolate from data performed in other age groups.