NDSR does not classify foods into the four NOVA categories. However, a researcher may carry out this classification for foods entered into NDSR dietary recall, record, and menu record types. There are multiple ways this may be done. Sneed et al. report on one approach using their NDSR data (1). These authors assess inter-rater reliability and note that their data files are available to researchers on request. Below we describe another potential approach.
Potential approach for classifying foods in NDSR dietary recall, record and menu record types into the four NOVA categories.
1) For your set of dietary recalls/records/menus identify all unique food IDs in output file 02 (file that lists foods at the whole food level).
2) Sort the list of unique food IDs by the NCC Database Food Group ID* to facilitate coding.
3) Review the unique food IDs in your dataset, and then develop coding rules that will allow for classifying each food ID into one of the four NOVA categories.
Some of the coding rules you develop may leverage the NCC Database Food Group ID. For example, you may decide to specify in your coding rules that all foods with an NCC Database Food Group ID of 63 (‘Fruits, fresh and unsweetened’) be coded into the NOVA class 1 (‘Unprocessed or minimally processed’) category.
For some types of restaurant and packaged foods you may decide to develop coding rules that require going to the food company website to locate the food’s ingredient statement so that a classification determination may be made. Note that ingredient information is generally not available in output file 01 (component ingredient file) for packaged foods. Ingredient information is generally available for restaurant foods, but it should not be relied on for determining classification because NCC formulations for both packaged and restaurant foods include only those food ingredients that contribute to the nutrient content of the food. As a result, ingredients included in small amounts that do not contribute to nutrient content, such as most food flavorings, colorings, emulsifiers, and preservatives, are generally not included in the formulation.
For some types of restaurant and packaged foods you may develop general rules that do not require locating the product ingredient statement. For example, you may establish a rule that all soft drinks be coded into NOVA class 4 because these products are generally formulated in a way that involves including one or more ingredients that conform with class 4 criteria.
For multi-ingredient home prepared foods (e.g. home-made lasagna, pizza, cookies, etc.) the ingredients used in preparing the food are available in output file 01 (component ingredient file), and may be used to guide food coding decisions for these types of foods.
4) After NOVA classification codes have been assigned to all unique food IDs in file 02, statistical analysis code may be written to assign NOVA classification codes to all foods in all records in file 02. Then, code may be written to create processed food variables of interest for your study (e.g. times per day ultra-processed foods were consumed; percent of total calories from ultra-processed foods, etc.).
* The NCC Database Food Group ID’s, categories, and names are provided in the NDSR file ‘Nccdbfg[insert version].txt in the ‘Database Documentation Files’ folder within the ‘Additional Files’ folder. For Windows installations, the Additional Files are located at C:\Users\Public\Documents\NCC\NDSR [insert version]\Additional Files\Database Documentation.
1. Sneed NM, Ukwuani S, Sommer E, Samuels L, Truesdale K, Matheson D, Noerper T, Barkin S, Heerman W. Reliability and Validity of Assigning Ultra-Processed Food Categories to 24-Hour Dietary Recall Data Collected Using the Nutrition Data System for Research (NDS-R). Current Developments in Nutrition 2022;6:778.
