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subgroup analysis. Analysis weights were appropriately revised following the recommended procedures for combining NHANES survey data.3 Data are weighted to reflect population estimates. Unweighted sample size is shown in the data tables in Appendix F.

Sodium from Foods

Estimates of food intake are derived from two 24-hour dietary recalls.4 The day 1 interview was conducted in person in the Mobile Examination Center of NHANES. The day 2 interview was conducted by telephone 3–10 days later. As part of the NHANES 24-hour recall interview on day 1, respondents are probed to provide details of the food consumed. These probes elicit information such as brand names, preparation method, the form of the food (such as frozen, canned, or fresh), and the type of food to assist in clarifying levels of sodium in the food consumed, as well as fat, calories, and other components and where the foods were obtained. Questions are not asked about salt used in cooking, recipes, or food preparation as part of the 24-hour recall. Rather, a set of health-related questions is administered separately and includes questions about salt use. Respondents are asked how often salt is used in cooking inside the home; this question refers only to ordinary or seasoned salt and not “lite” salt or salt substitutes. Response options include “never,” “rarely,” “occasionally,” and “very often.” This information is applied to algorithms for recipes and sodium absorbed in cooking (Moshfegh, 2009).

A statistical method for estimating usual intake distributions and the proportion below or above defined cutoff values has been developed at Iowa State University and makes use of the second-day dietary recall for this purpose (Carriquiry, 2003). This method was applied to estimates of sodium intake for this study, where possible. Certain measures of interest were not applicable to use of this software and were reported as 1-day means; these include estimates of sodium intake from other sources such as tap water.

Sodium from Other Sources

Other sources of sodium include salt added at the table, tap water, and dietary supplements. The approach used to estimate this intake was developed for the Healthy People 2010 Progress Review, Focus Area 19,


Available online: (accessed March 25, 2010).


Available online: (accessed October 26, 2009).

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