Intake data from food, water, and, when available, supplements and some over-the-counter medications are used for several purposes in this report: to estimate the average requirement of a nutrient, to determine the lowest-observed-adverse-effect level (LOAEL) or the no-observed-adverse-effect level (NOAEL) of a nutrient, and to characterize the risk of exceeding the UL for a nutrient. They are also used in a few examples of applying DRIs to specific situations.
Availability of nutrients from a range of foods provides useful information when setting nutrient requirements and ULs. Calcium in the United States and Canada is obtained primarily from dairy products (Cleveland et al., 1996; NIN, 1995). Household consumption data show that individuals in the United States consume the equivalent of 2 cups of milk per day (based on the calcium content of various dairy products), while Canadians consume approximately 1.6 cups per day (Cleveland et al., 1996; NIN, 1995).
For this report, consideration of the dietary practices associated with intakes of calcium and related nutrients has been limited to observations within U.S. and Canadian populations. The recommendations for the DRIs may not be generalizable globally, especially where food intake and indigent dietary practices may result in very different bioavailability of mineral elements from sources not considered in traditional diets of Canadians and Americans. For example, both the consumption of bones from fish and meat foods and the practice of geophagia are more common in developing countries than in the United States or Canada. Population variations in the consumption of other diet components such as protein and sodium may significantly affect population calcium and magnesium needs and ULs.
With regard to the need for calcium and related nutrients for bone health, cross-cultural comparisons must also consider variability among populations in activity, weight-bearing practices, and sun exposure. Differences in hip axis length or other structural features may vary across cultures; hip axis length is directly associated with hip fracture risk (Cummings et al., 1993). Until more is learned about the prevalence of osteoporosis and hip fracture risk