Methodologic differences in dietary supplements data collection and processing between the Third National Health and Nutrition Examination Survey (NHANES III) and the continuous NHANES (1999‐2006)

Abstract

Dietary supplement data has been collected for many years in the National Health and Nutrition Examination Survey (NHANES). Over time, the methods used to collect self‐reported information on dietary supplement use have changed within NHANES. For example, different questions have been asked at different time periods. In addition, the methods of attaining and coding ingredient information about the supplement products have also changed. An example is the use of different methods for assigning default strengths to single and multiple nutrient/ingredient products. The overall prevalence of dietary supplement use increased from 41.3% (NHANES III) to 53.4% (NHANES 2003‐2006). The purpose of this study was to determine if it is possible to quantify how much (if any) of this observed increase in dietary supplement use might be due to the changes in collection, processing and coding of the data that occurred between the two survey time periods.