Using Output-related FAQs


How do I calculate nutrient intake from food and dietary supplement sources?

Overview

If dietary supplement use was assessed using the Dietary Supplement Assessment Module (DSAM), nutrient intakes from food and dietary supplement sources combined may be calculated using Output File data in File 04 (Intake Properties Totals File) and File 12 (DSAM Total 24-hour Supplement Intake File). File 04 contains total daily nutrient intake estimates from the 24-hour dietary recall record (e.g., total daily vitamin C intake from the 24-hour dietary recall record). File 12 includes total daily nutrient intake estimates from the DSAM interview (e.g., total daily vitamin C intake from the 24-hour dietary supplement recall interview). By summing nutrient intake estimates from File 04 and File 12, total daily intake of nutrients from food and supplement sources may be calculated (e.g., vitamin C intake from 24-hour dietary recall record + vitamin C intake from 24-hour dietary supplement recall interview = total vitamin C intake from all sources combined).
 
Nutrients and Food Components for Which Totals May be Calculated
Nutrients with common units and definitions in File 04 and File 12 may be combined to calculate total intake estimates. A listing of variable names and file locations (column numbers) for nutrients with the same units in File 04 and File 12 are provided herein to assist in this process (pdf).  Comments are provided to explain the rationale for some of the combinations.

 

It is important to note that File 04 contains some nutrients and food components that are not included in File 12. For example, the variable ‘maltose’ is included in File 04 but is not available in File 12. Conversely, File 12 contains some nutrients and dietary supplement components that are not included in File 04. For example, the variable ‘chromium’ is included in File 12 but is not available in File 04. Consequently, total intake estimates from food and dietary supplement sources combined may not be calculated for these nutrients and food components.
 
It is also important to note that nutrients with different units or descriptions should not be combined unless conversion factors are available (see the Alerts and Footnotes in the pdf). For example, multiply the Synthetic Folate (folic acid) value in Supplements by a factor of 1.7 to convert to Dietary Folate Equivalents in Supplements or divide the Omega-3 Fatty Acids value in Supplements by 1000 to convert from milligrams to grams.
 
Dietary Supplement Intake Data Caveats
All nutrient values and other components assigned to dietary supplements in the DSAM database are limited to the information provided on the product’s Supplement Facts panel. Dietary supplement manufacturers have some discretion with respect to the information they provide on this panel. Most notably, they are not required to list on the Supplement Facts panel all of the nutrients the product contains. Since NCC does not calculate or impute nutrients for dietary supplements, the level of completeness for some nutrients and components may therefore be low. Due to this limitation, the nutrient totals may be under-estimated for some nutrients because the DSAM database does not contain the usual relationships to other nutrients or components.
 
Some examples of nutrients and other supplement components for which completeness may be an issue are as follows:
 
Amino Acids
The amount of protein contained in a ‘serving’ of a dietary supplement must be provided on the Supplement Facts panel if a product contains protein. The individual amino acids in a protein containing supplement may be listed, but inclusion on the Supplement Facts panel is not mandatory. As a result, amino acid information for protein containing products may be incomplete.
 
Fatty Acids
The amount of fat contained in a ‘serving’ of a dietary supplement must be provided on the Supplement Facts panel if a product contains fat. Likewise, the total saturated and trans fatty acid content must be listed. Other classes of fatty acids and individual fatty acids do not have to be provided. However, manufacturers may provide this information if they wish. Consequently, fatty acid information for fat containing products may be incomplete.
 
Soluble and Insoluble Fiber
The amount of fiber contained in a ‘serving’ of a dietary supplement must be provided on the Supplement Facts panel of fiber containing supplements. The amounts of soluble and insoluble fiber do not have to be provided. However, manufacturers may provide this information if they wish. As a result, soluble and insoluble fiber information may be incomplete for some fiber containing products.
 
Total Vitamin A
Starting in 2016 when the FDA published the final rule for the new Nutrition Facts panel for foods and Supplement Facts panel for dietary supplements, vitamin A could be included on product labels in either Retinol Activity Equivalents (RAE) (mcg) or International Units (IU).  The new Supplement Facts panel, which manufacturers could begin using anytime between the final rule and mandatory implementation in 2020, requires vitamin A to be listed on the label in the unit of mcg RAE whereas the old label required listing vitamin A in IU.  As a result of this labeling change, starting in NDSR 2020 vitamin A containing products in the DSAM database may include vitamin A values in either mcg RAE or IU.
 
There is no direct conversion factor from the vitamin A declared on labels in IU to mcg RAE, only individual conversion factors for provitamin A carotenoids and pre-formed vitamin (https://www.fda.gov/media/129863/download).  Consequently, Total Vitamin A Activity (International Units) (IU) from Files 04 and 12 can be combined and Total Vitamin A Activity (Retinol Activity Equivalents) (mcg) from Files 04 and 12 can be combined but the two cannot be combined to calculate one Total Vitamin A value from foods and supplements.
 
Total Vitamin E
Starting in 2016 when the FDA published the final rule for the new Nutrition Facts panel for foods and Supplement Facts panel for dietary supplements, vitamin E could be included on product labels in either Total Alpha-Tocopherol (mg) or International Units (IU). The new Supplement Facts panel, which manufacturers could begin using anytime between the final rule and mandatory implementation in 2020, requires vitamin E to be listed on the label in the unit of Total Alpha-Tocopherol (mg) whereas the old label required listing vitamin E in IU.  As a result of this labeling change, starting in NDSR 2020 vitamin E containing products in the DSAM database may include vitamin E values in either Total Alpha-Tocopherol (mg) or IU.
 
Without knowing the form of vitamin E (i.e. natural RRR-α-tocopherol vs. synthetic all-rac-α-tocopherol), there is no direct conversion factor from the vitamin E declared on labels in IU to mg of Total Alpha-Tocopherol.  Consequently, Vitamin E (International Units) (IU) from Files 04 and 12 can be combined and Vitamin E (Total Alpha-Tocopherol) (mcg) from Files 04 and 12 can be combined but the two cannot be combined to calculate one Total Vitamin E value from foods and supplements.

Why doesn't the sum of the sugars, dietary fiber, and starch equal the value for total carbohydrate in NDSR?

The values for the three components of the carbohydrate are often taken from a variety of sources, mainly food analyses appearing in the scientific literature. Generally, for a single food entry, the fiber value is from one data source, the sugar values from another, and the starch value from a third. The total carbohydrate value is usually from the USDA Nutrient Data Laboratory database. Since the data were obtained from a variety of sources, and therefore a variety of food samples, the individual carbohydrate fractions do not necessarily equal the total carbohydrate.
 
Even if the carbohydrate values are all taken from the same source, there may be a difference between the total carbohydrate and the sum of the fractions. This is because the total carbohydrate for 100 grams of food is derived by subtracting the amount of fat, protein, ash, and water from 100 grams. Therefore, the resulting total carbohydrate may include compounds other than sugars, dietary fiber, and starch.
Additionally, the NCC Food and Nutrient Database contains fields for sucrose, glucose, fructose, lactose, maltose, and galactose. There are many other sugars in foods that are not yet included in the database due to inadequate data.

Can I analyze my NDSR data for high fructose corn syrup intake?

The short answer is ‘no’. Some NDSR users have wondered if they could create an estimate of HFCS by totaling fructose and glucose, two sugars that are included in the NCC Food and Nutrient Database. This approach is problematic because high fructose corn syrups are just one source of these sugars.
 
Added Sugars (by Available Carbohydrate) and Added Sugars (by Total Sugars) are included in the database, and depending on your research question, may be useful to you. It is also possible to estimate intake of food categories that tend to include products that contain high fructose corn syrup. For example, servings of sweetened soft drinks may be estimated using the NCC Food Groups Serving Count System.

Why are the grains in ounce equivalents columns blank?

The USDA Food Pattern Equivalent grain variables (total, whole, and refined grains) will not be calculated for data collected from versions prior to NDSR 2013. If older data are rerun, the grain per ounce equivalent categories will be in the output files, but data will be missing or blank for these variables. See “The USDA Food Patterns Equivalents Grain Variables” in Appendix 10, Food Grouping” for more information on equivalent grain variables.

How do I open my output in Microsoft Excel and view it?

If you plan to analyze your data using Excel, you may want to generate the output files with the headers. Once you have generated the output, you will first need to extract the output files. Then open Excel, select Open from the File menu, and browse to the location of the output file you wish to open. Change the “All Excel Files” option to “All Files” in the drop down menu above the Open button, then select the file you want to open. A Text Import Wizard in Excel will pop up and should already recognize that the .txt files are tab delimited. Select “finish” to open the file.