Task 2: Key Concepts about Identifying Food Frequency Variables and File Locations

NHANES food frequency variables cover a range of items related to the consumption of foods and food groups during the previous 12 months.  These variables, and information about the variables, are stored within the DIetary component and are contained in two separate data files that reflect responses to the NHANES Food Frequency Questionnaire (FFQ):

The variables in the FFQ Questionnaire File represent the actual questionnaire responses.  The raw responses were processed using special software (DietCalc) to produce the second file, the FFQ Average Daily Frequency Covariates File.  DietCalc has food grouping algorithms which derive average daily frequencies  

Each survey participant has one record in the FFQ Questionnaire File, whereas each participant has multiple records in the FFQ Average Daily Frequency Covariates File.

The NHANES food frequency variables and their respective files are divided within the Examination component of the survey, as follows:


Variables in the FFQ Questionnaire File:

The file has a large number of variables, so it is especially important to review the codebook and documentation.  The variables in this file include:


Variables in the FFQ Daily Frequency Covariates File:

The file contains five variables as listed below.  Two of these variables are linked to look-up files that provide descriptive information.


For more detail on the food frequency variables, go to Information about Dietary Variables.  Please note, however, that the most complete descriptions of these variables can be found in the Analytic Notes section of the “Docs” files. 



Food frequency data are part of the Dietary component of NHANES 2003-2004.  Other variables necessary for your analysis may be located in other parts of the dataset.


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