. "Appendix E: Background on the National Health and Nutrition Examination Surveys and Data Analysis Methods." Strategies to Reduce Sodium Intake in the United States. Washington, DC: The National Academies Press, 2010.
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Strategies to Reduce Sodium Intake in the United States
presented April 20085,6 and described as part of the Healthy People 2010 tracking system.7
Accurate reporting of salt used at the table relies on subjects’ ability to estimate the quantity and frequency with which salt is added to foods. For NHANES, respondents are asked to indicate how often salt is added at the table.8 Response options include “never,” “rarely,” “occasionally,” and “very often.” Sea salt, flavored salts (such as garlic or onion salt), and seasoning salts were counted as ordinary salts. So-called lite salt was recorded as such and has a reduced sodium content. Salt substitutes do not contain sodium. When an analysis incorporates use of salt at the table in the estimation of sodium intake, the amount of sodium depending on salt type is multiplied by the frequency value (i.e., sodium in type of salt multiplied by frequency amount of sodium from table salt added per day) to obtain a daily amount for each person. Regarding type of salt, a zero sodium value is assigned for reports of “none” and “salt substitute.” When “very often” was reported for use, ordinary salt is assigned as 290 mg sodium for persons ages 2–19 years, and 580 mg for persons over 20 years of age. If salt use was reported as “occasionally,” the value for “very often” was multiplied by one-half; for reports of use as “rarely,” the value for “very often” was multiplied by one-fourth.
When an analysis incorporates sodium from drinking water, water derived from a water softening or conditioning system is identified as containing 3 mg of sodium per fluid ounce. Otherwise, water is counted as unsoftened. One mg sodium per fluid ounce is used for “regular” municipal water based on the USDA food composition database. In WWEIA 2003–2004, only sweetened bottled waters were captured in the 24-hour recall. Information on plain water, tap water (and source), and plain carbonated water was captured in survey questions following the 24-hour recall. For the analysis in this report, waters were categorized as tap water (for the tap water contribution), and other bottled and sweetened waters were categorized as foods in the beverage category.
Finally, data on dietary supplements are collected as part of NHANES, but the incorporation of sodium from dietary supplements requires additional data permutations to link the dietary supplement data set to the foods intake data set. To make this calculation, the content of each dietary supplement reported by the respondent and the frequency of use in the past