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DRI Dietary Reference Intakes Calcium Vitamin D
levels for Canadians are collected for persons between the ages of 6 and 79 years. However, in arranging these data from survey age/sex groups into the DRI life stage groups, sample sizes did not allow adequate representation for children less than 9 years of age. Therefore, the data were used to construct values for the DRI life stage groups only between ages 9 to 79 years for Canadians. In addition, neither country reports data for infants 0 to 12 months of age or for pregnant and lactating women; sample sizes for these groups are too low in the surveys to provide nationally representative estimates.
United States: The National Health andNutrition Examination Survey
Information about the U.S. National Health and Nutrition Examination Survey (NHANES) is available from the survey’s main website,1 and is therefore only summarized here. In the 1960s, the U.S. government initiated the National Health Examination Survey to assess the health status of individuals ages 6 months through 74 years. Nutritional intake was added as a survey component in the 1970s, beginning with the first NHANES, known as NHANES I (1971 to 1974). NHANES II covered the time period 1976 to 1980, and NHANES IIII encompassed 1988 to 1994. NHANES has reflected a continuous and standardized data collection based on a representative sample of the U.S. population and provides critical diet and health measures for federal program planning and policy making. The survey relies on the gold standard for dietary intake measures, two or more 24-hour dietary recalls per person (IOM, 2000). The U.S. Department of Agriculture’s (USDA’s) food composition database has provided the sources of information that allow the estimates of food intake collected in the NHANES to be translated into quantitative nutrient intake (Bodner-Montville et al., 2006; Briefel, 2006).
In 1999, the survey became a continuous program that has a changing focus on a variety of health and nutrition measurements to meet emerging needs;2 the survey data are reported on the basis of 2-year periods. The survey now examines a nationally representative sample of about 5,000 persons each year. These persons are located in counties across the country, 15 of which are visited each year.3 The NHANES and related food intake surveys conducted by the USDA were integrated in 2002; at that time, the
