Monitoring sodium intake of the US population: impact and implications of a change in what we eat in America, National Health and Nutrition Examination Survey dietary data processing

Abstract

Accurate monitoring of US sodium intake requires familiarity with national dietary data collection and processing procedures. This article describes a data processing step that impacts sodium intake estimates, reasons for discontinuing the step, and implications of its discontinuation. This step, termed salt adjustment, was performed in US Department of Agriculture (USDA) dietary intake surveys from 1985 through 2008. In What We Eat in America (WWEIA), the dietary intake interview component of the National Health and Nutrition Examination Survey (NHANES), the salt content of specific foods was reduced on the basis of a question about household use of salt in cooking. For individuals whose households used salt in cooking occasionally or less often, some or all of the salt attributable to home preparation was removed from foods that typically have salt added during preparation and were obtained from the store. The growing availability of preprepared foods in stores challenges the validity of using store purchase as a proxy indicator of home food preparation, and increased restaurant/fast-food consumption implies fewer reported foods are eligible for the procedure. In addition, USDA's Automated Multiple-Pass Method for the 24-hour dietary recall provides accurate sodium intake estimates without applying the salt-adjustment step. The final WWEIA, NHANES data release to contain salt-adjusted sodium data was 2007-2008. When assessing the effectiveness of sodium-reduction efforts over time, the nutrition community (eg, researchers, analysts, providers) must be aware of this change in WWEIA, NHANES beginning in 2009-2010 and account for it using appropriate baseline estimates.